THE SPECIFICATIONS AND INFORMATION REGARDING THE PRODUCTS IN THIS MANUAL ARE SUBJECT TO
CHANGE WITHOUT NOTICE. ALL STATEMENTS, INFORMATION, AND RECOMMENDATIONS IN THIS
MANUAL ARE BELIEVED TO BE ACCURATE BUT ARE PRESENTED WITHOUT WARRANTY OF ANY KIND,
EXPRESS OR IMPLIED. USERS MUST TAKE FULL RESPONSIBILITY FOR THEIR APPLICATION OF ANY
PRODUCTS.
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Tel: 408 526-4000
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Text Part Number: OL-17309-02
THE SOFTWARE LICENSE AND LIMITED WARRANTY FOR THE ACCOMPANYING PRODUCT ARE SET FORTH IN THE
INFORMATION PACKET THAT SHIPPED WITH THE PRODUCT AND ARE INCORPORATED HEREIN BY THIS REFERENCE. IF YOU
ARE UNABLE TO LOCATE THE SOFTWARE LICENSE OR LIMITED WARRANTY, CONTACT YOUR CISCO REPRESENTATIVE FOR A
COPY.
The following information is for FCC compliance of Class A devices: This equipment has been tested and found to comply with the limits for a Class
A digital device, pursuant to part 15 of the FCC rules. These limits are designed to provide reasonable protection against harmful interference when
the equipment is operated in a commercial environment. This equipment generates, uses, and can radiate radio-frequency energy and, if not installed
and used in accordance with the instruction manual, may cause harmful interference to radio communications. Operation of this equipment in a
residential area is likely to cause harmful interference, in which case users will be required to correct the interference at their own expense.
The following information is for FCC compliance of Class B devices: The equipment described in this manual generates and may radiate
radio-frequency energy. If it is not installed in accordance with Cisco’s installation instructions, it may cause interference with radio and television
reception. This equipment has been tested and found to comply with the limits for a Class B digital device in accordance with the specifications in
part 15 of the FCC rules. These specifications are designed to provide reasonable protection against such interference in a residential installation.
However, there is no guarantee that interference will not occur in a particular installation.
Modifying the equipment without Cisco’s written authorization may result in the equipment no longer complying with FCC requirements for Class
A or Class B digital devices. In that event, your right to use the equipment may be limited by FCC regulations, and you may be required to correct
any interference to radio or television communications at your own expense.
You can determine whether your equipment is causing interference by turning it off. If the interference stops, it was probably caused by the Cisco
equipment or one of its peripheral devices. If the equipment causes interference to radio or television reception, try to correct the interference by
using one or more of the following measures:
• Turn the television or radio antenna until the interference stops.
• Move the equipment to one side or the other of the television or radio.
• Move the equipment farther away from the television or radio.
• Plug the equipment into an outlet that is on a different circuit from the television or radio. (That is, make certain the equipment and the television
or radio are on circuits controlled by different circuit breakers or fuses.)
Modifications to this product not authorized by Cisco Systems, Inc. could void the FCC approval and negate your authority to operate the product.
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The use of the word partner does not imply a partnership relationship between Cisco and any other company. (1110R)
AC Power2-5
Site Environment2-5
Site Configuration: Maintaining Normal Operation2-6
General Precautions2-6
Power Considerations2-7
Required Network Information2-7
Before You Begin2-7
Installation Tools2-8
Rack-Mount and Cable-Management Kit2-8
Equipment Required to Verify Your Plant’s RF Setup2-9
Shipping Container Contents2-9
Verifying the Shipping Container Contents2-9
Provisioning the Cable Headend2-10
Two-Way Data and VoIP2-10
Headend Certification2-11
Diplex Filters2-11
Receivers2-11
DHCP, DNS, TFTP, and TD Servers2-12
Telco Return2-12
Dial-Up/Remote Access Servers2-12
RADIUS Dial Security Servers2-12
Authentication, Authorization, and Accounting Servers2-13
VoIP Gateways and Gatekeepers2-13
VoIP SGCP Pass-Through2-13
Headend Wiring2-14
Interference Considerations2-14
Distance Limitations and Interface Specifications2-14
Equipment Racks 2-15
Installing Rack-Mount Brackets on the Rear of the Chassis3-7
Installing Rack-Mount Brackets on the Front of the Chassis3-8
Installing Rack-Mount Brackets in the Middle of the Chassis3-9
Installing the Chassis in the Rack3-10
Installing the Chassis in a Workbench or Tabletop Environment3-12
Installing the Cable-Management Bracket on a Cisco uBR7225VXR Router in a Workbench or
Tabletop Environment3-13
Cabling3-13
Connecting Cable Interface Line Card Cables3-14
Console and Auxiliary Port Connection Equipment3-14
Console Port Signals3-15
Auxiliary Port Signals3-15
Protective Grounding3-16
Connecting Power3-16
Connecting to the AC-Input Power Supply3-17
Contents
CHAPTER
Powering On the Cisco uBR7225VXR Router3-18
Configuring the Interfaces3-19
4Connecting the Cisco uBR7225VXR Router to the Cable Headend4-1
Two-Way Data Headend Architecture4-2
One-Way Data Headend Architecture4-3
RF and Digital Data Overview4-3
Connecting and Configuring the Downstream4-4
Installing and Configuring the Upconverter4-4
Measuring the Downstream RF Signal4-4
Measuring the Downstream RF Signal Using the Channel Power Option on a Spectrum Analyzer4-5
Measuring the Downstream IF Signal at the Cisco uBR7225VXR Router4-5
Measuring the Downstream RF Signal at the Upconverter Output4-7
Measuring the Downstream RF Signal Using CATV Mode on a Spectrum Analyzer4-11
Measuring the Downstream IF Signal at the Cisco uBR7225VXR Router Using CATV Mode4-11
Measuring the Downstream RF Signal at the Upconverter Output Using CATV Mode4-14
Connecting and Configuring the Upstream4-18
Connecting the Upstream to the Optical Receiver4-18
Testing the Upstream Configuration4-19
OL-17309-02
Measuring the Upstream RF Signal4-22
Measuring the Upstream RF Signal Using a Spectrum Analyzer4-22
Analyzing the Upstream RF Signal4-25
Using the Zero-Span Method with Adjacent Upstream Channels4-28
This preface describes the objectives, intended audience, and organization of this document and explains
how to find additional information on related products and services.
This preface contains the following sections:
• Document Revision History, page ix
• Document Objectives, page ix
• Audience, page x
• Document Organization, page x
• Document Conventions, page xi
• Obtaining Documentation and Submitting a Service Request, page xii
Document Revision History
The Document Revision History table below records technical changes to this document.
RevisionDateChange Summary
OL-17309-01December 15, 2008 Original publication.
OL-17309-02August 2012Added information about the new 540 W AC-input power
Document Objectives
This guide provides hardware installation instructions for the Cisco uBR7225VXR universal broadband
router.
The guide contains procedures to unpack, install, and connect the Cisco uBR7225VXR router hardware
that enables your cable television (CATV) headend or distribution hub to support digital data and
Voice-over-IP (VoIP) services. The guide includes procedures to characterize your cable plant to ensure
that data services are reliably supported over the cable infrastructure.
This guide is intended for cable system installers and technicians who physically install and connect the
Cisco uBR7225VXR universal broadband router and associated equipment at the cable headend or
distribution hub. Cable system installers and technicians should be familiar with their cable plant base
operating parameters and service offerings.
The guide provides limited configuration information. After following applicable procedures in this
guide, refer to the “Obtaining Documentation and Submitting a Service Request” section on page xii for
related Cisco publications that more completely address configuration.
Warning
Only trained and qualified personnel should be allowed to install, replace, or service this equipment.
Statement 1030
Document Organization
This hardware installation guide is organized into the following chapters and appendixes:
Chapter TitleDescription
Chapter 1, “Cisco uBR7225VXR
Overview”
Chapter 2, “Preparing the
Cisco uBR7225VXR Router for
Installation”
Chapter 3, “Installing the
Cisco uBR7225VXR Router”
Chapter 4, “Connecting the
Cisco uBR7225VXR Router to the
Cable Headend”
Chapter 5, “Maintaining the
Cisco uBR7225VXR Router”
Appendix A, “Cisco uBR7225VXR
Router Specifications”
Appendix B, “RF Specifications”Recommended RF settings at the headend for both Data-over-Cable Service
Appendix C, “Cable Specifications”Cable and cable pinout information for the Cisco uBR7225VXR router.
Appendix D, “Industry-Standard Wiring
Plans”
Appendix E, “Frequency Allocation
Tables ”
About Cisco uBR7225VXR chassis and components.
Safety considerations, tools, and other equipment required to prepare your site.
Installing the chassis and connecting the power and network interface cables.
Connecting the Cisco uBR7225VXR router to a hybrid fiber-coaxial (HFC)
network and configuring and measuring downstream and upstream portions of the
HFC network.
Basic hardware maintenance instructions.
System specifications.
Interface Specifications (DOCSIS) and EuroDOCSIS networks.
The telephone industry color-code schemes for 25-pair wires including the pin
numbers, optical fibers, and small wire pairs.
Information on the National Television System Committee (NTSC) frequency
map for 6-MHz channel bands and the Phase Alternating Line (PAL) and
SEquential Couleur Avec Memoire (SECAM) frequency map for 8-MHz channel
bands.
Appendix F, “Manufacturers for Headend
Provisioning Requirements”
Manufacturers and websites required to prepare and provision a North American
or a European cable headend to support digital data.
Appendix G, “Site Log”Example of a cable headend site log—Use to keep a historical record of actions
relevant to the Cisco uBR7225VXR router installation, operations, and
maintenance.
Document Conventions
This publication uses the following conventions:
• The symbol ^ represents the key labeled Control. For example, the key combination ^z means hold
down the Control key while you press the z key.
Command descriptions use these conventions:
• Examples that contain system prompts denote interactive sessions, indicating the commands that
you should enter at the prompt. The system prompt indicates the current level of the EXEC
command interpreter. For example, the prompt
and the prompt
Router# indicates that you should be at the privileged level.
Access to the privileged level usually requires a password. For additional information, refer to the
related software configuration and reference documentation listed in the Cisco uBR7200 Series Software Configuration Guide at the following URL:
Router> indicates that you should be at the user level,
TimesaverMeans the described action saves time. You can save time by performing the action described in the
paragraph.
TipMeans the following information might help you solve a problem.
For all warning translations, refer to the Regulatory Compliance and Safety Information for Cisco uBR7200 Series Universal Broadband Routers at the following URL:
This warning symbol means danger. You are in a situation that could cause bodily injury. Before you
work on any equipment, be aware of the hazards involved with electrical circuitry and be familiar
with standard practices for preventing accidents. Use the statement number provided at the end of
each warning to locate its translation in the translated safety warnings that accompanied this device.
Statement 1071
SAVE THESE INSTRUCTIONS
Obtaining Documentation and Submitting a Service Request
For information on obtaining documentation, submitting a service request, and gathering additional
information, see the monthly What’s New in Cisco Product Documentation, which also lists all new and
revised Cisco technical documentation, at:
Subscribe to the What’s New in Cisco Product Documentation as a Really Simple Syndication (RSS)
feed and set content to be delivered directly to your desktop using a reader application. The RSS feeds
are a free service and Cisco currently supports RSS version 2.0.
• Supported System Configurations Overview, page 1-6
• Hardware Component Descriptions, page 1-10
Cisco uBR7225VXR Universal Broadband Router
The Cisco uBR7200 series universal broadband routers, part of the Cisco Cable Modem Termination
System (CMTS) solution, allows high-speed data services to be packaged similar to basic cable
television service or video fare.
1
The router is based on Data-over-Cable Service Interface Specifications (DOCSIS) and supports data
and packetized voice connectivity over a bidirectional cable television and IP backbone network. The
Cisco uBR7200 series universal broadband routers typically concentrates traffic from DOCSIS- or
EuroDOCSIS-based cable interfaces and cable modems (or set-top boxes with integrated DOCSIS or
EuroDOCSIS cable modems) on the cable television network and presents that traffic to local and remote
IP hosts. For cable plants not fully upgraded to support two-way cable transmission, the router works in
conjunction with dial-up access products to support upstream traffic from DOCSIS-based cable
interfaces connected to the Public Switched Telephone Network (PSTN). The router supports both
6-MHz North American channel plans using ITU-T J.83 Annex B operation and 8-MHz Phase
Alternating Line (PAL) and SEquential Couleur Avec Memoire (SECAM) channel plans using ITU-T
J.83 Annex A operation.
The Cisco uBR7200 series universal broadband routers contains some or all of the following:
• Cable interface line cards that interface to the cable television network. The Cisco uBR7225VXR
card set includes varying upstream-to-downstream interface ratios with differing bandwidth and
modulation schemes supported, as well as the capability to dynamically perform complex spectrum
management and operate in a 6-MHz or 8-MHz channel width environment.
See the “Cisco Cable Interface Line Cards” section on page 1-12.
• One network processing engine (NPE) that performs system management functions for the chassis.
See the “Network Processing Engine” section on page 1-10.
• The Cisco uBR7225VXR router supports an optional redundant power supply. See the “Power
• A midplane that serves as the interconnect between the cable interface line cards and the other
components of the system. See the “Subchassis and Midplane” section on page 1-17.
• A fan tray, enclosing internal fans that draw cooling air into the chassis to maintain an acceptable
operating temperature. See the “Fan Trays” section on page 1-14.
The cable interface cards, NPE, and power supplies slide into their respective chassis slots and connect
directly to the router midplane. There are no internal cables to connect. The midplane distributes power
from the power supplies to the cable interface cards, fan tray, and NPE.
The Cisco uBR7225VXR universal broadband router may be installed on a tabletop or rack-mounted. A
rack-mount kit ships with each router. The rack-mount kit includes the hardware needed to mount the
router in a standard 19-inch equipment rack or telco-type rack.
The Cisco uBR7200 series universal broadband routers supports:
• Environmental monitoring and reporting functions to resolve adverse environmental conditions
before loss of operation.
• Online insertion and removal (OIR), allowing key system components to be added or removed
without powering off the chassis.
Chapter 1 Cisco uBR7225VXR Overview
CautionYou can remove and replace a cable interface line card with the same type of component without
interrupting the rest of the system or having to reconfigure the system. However, to replace a
cable interface line card with a different type of card (for example, hot swapping from a
Cisco uBR-MC16U cable interface line card to a Cisco uBR-MC28U cable interface line card), you must
copy your startup configuration to your running configuration on the Cisco uBR7225VXR router to
enable the interfaces on the new cable interface line card.
CautionThe NPE does not support OIR. You must power down the chassis before removing the NPE.
NoteFor specific instructions to install, remove, or replace system components, refer to the documentation at
The front of the Cisco uBR7225VXR chassis provides access to two cable interface line cards. See
Figure 1-1.
The rear of the Cisco uBR7225VXR provides access to the network processing engine and up to two
power supplies. See Figure 1-2.
A fully configured Cisco uBR7225VXR router can operate with only one installed power supply;
however, a second, optional power supply of the same type provides hot-swappable, load-sharing, and
redundant power. In a chassis using two power supplies, if one power supply fails or is removed, the
redundant power supply immediately takes over the router’s power requirements and maintains normal
operation without interruption.
The power supply has the router’s main power switch and an AC-input power receptacle. Mounting holes
for a ground lug are located on the far right side on the rear of the chassis, to provide a chassis ground
connection for ESD-preventive equipment. See Figure 3-13 on page 3-16.
Cisco uBR7225VXR Universal Broadband Router
NoteFigure 1-2 shows the rear of a Cisco uBR7225VXR router configured with two 300W AC-input power
supplies.
CautionIf you are using two power supplies, make sure that each one is plugged into a separate branch circuit.
A fully loaded router, with two installed power supplies (300 W) and all chassis slots filled, weighs
approximately 48 pounds (21.8 kg). For clearance requirements and rack-mount installation
considerations, refer to the “Site Environment” section on page 2-5.
This section provides a functional overview of the network interfaces available on the
Cisco uBR7225VXR universal broadband router, cable interface line card slot and logical interface
numbering, as well as the MAC address assignments for cable interface line card interfaces.
Card Slot and Logical Interface Numbering
In the Cisco uBR7200 series universal broadband routers, the slot number is the chassis slot in which a
cable interface card is installed.
Cable interface line card slots maintain the same slot number regardless of whether other cable interface
line cards are installed or removed. However, when you move a cable interface line card to a different
slot, the logical interface number changes to reflect the new slot number.
The MAC-layer or hardware address is a standardized data-link layer address that is required for certain
network interface types. These addresses are specific and unique to each port. The Cisco uBR7225VXR
uses a specific method to assign and control the MAC-layer addresses of its port adapters. For a
description of the MAC-layer address, refer to the “MAC-Layer Address” section on page 1-5.
1-4
The two cable interface line cards in the Cisco uBR7225VXR router provide the connection between the
router’s two PCI buses (mb1 and mb2) and external networks. See Figure 1-3.
Figure 1-3Cisco uBR7255VXR Chassis and Cable Interface Line Cards
Cisco uBR7225VXR Network Interface Overview
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MAC-Layer Address
All LAN interfaces (ports) require unique MAC-layer addresses, also known as hardware addresses.
Typically, the MAC address of an interface is stored on a memory component that resides directly on the
interface circuitry; however, the OIR feature requires a different method. For a description of OIR, refer
to the “Online Insertion and Removal” section on page 5-1.
The OIR feature allows you to remove a cable interface line card and replace it with another identically
configured one. If the new cable interface line card matches the cable interface line card you removed,
the system immediately brings it online. In order to allow OIR, an address allocator with a unique MAC
address is stored in EPROM on the Cisco uBR7225VXR universal broadband router midplane. Each
address is reserved for a specific slot in the router regardless of whether a cable interface line card
resides in that slot.
The MAC addresses are assigned to the slots in sequence. This address scheme allows you to remove
cable interface cards and insert them into other universal broadband routers without causing the MAC
addresses to move around the network or be assigned to multiple devices.
NoteStoring the MAC addresses for every slot in one central location means that the addresses stay with the
memory device on which they are stored.
Cable interface line card slot 2
2
OL-17309-02
For information on the commands used to configure your Cisco uBR7225VXR router, refer to the Cisco
IOS Configuration Fundamentals Configuration Guide at the following URL:
The Cisco uBR7200 series universal broadband routers is installed at a cable television headend or a
distribution hub. Related networking and RF equipment, servers, and other host computers are installed,
along with the Cisco uBR7225VXR router, to support digital data transmission.
To deliver data and VoIP services over the cable television system, TV channels are allocated to carry
digital data. Data is modulated downstream on:
• 6-MHz channels in the 88 to 860 MHz range, using North American channel plans through
Cisco cable interface line cards installed in the chassis. For bidirectional cable plants, a portion of
the 5 to 42 MHz range is used for upstream data transmission. For one-way cable plants or cable
segments yet to be upgraded, DOCSIS-based cable interfaces configured for telco return are also
supported.
• 8-MHz channels in the 108 to 862 MHz range using PAL/SECAM channel plans through
Cisco cable interface line cards installed in the chassis. For bidirectional cable plants, a portion of
the spectrum in the 5 to 65 MHz range is used for upstream data transmission.
• 6-MHz channels in the 70 to 860 MHz range, using J-DOCSIS channel operation (extensions for
Japan and select regions) through Cisco cable interface line cards installed in the chassis. For
bidirectional cable plants, a portion of the 5 to 55 MHz range is used for upstream data transmission.
The following sections illustrate the supported configurations including:
Chapter 1 Cisco uBR7225VXR Overview
• Basic Internet access services
• Virtual private network (VPN) services
• IP telephony services
• Telco return
Basic Internet Access Services
A Cisco uBR7225VXR universal broadband router is installed at the headend or distribution hub. The
Cisco uBR7225VXR downstream cable interface line cards, with onboard upconvertor, translate the
downstream signals to RF for broadcast. The Cisco uBR7225VXR router enables you to transmit
downstream data in both the 6-MHz North American or Japanese and the 8-MHz European channel
environments using the appropriate model of the cable interface line card.
Receivers, scramblers, and descramblers process the television signals to encode or decode signals as
needed for broadcast. Modulators format the analog television and digital signals while upconverters
change the carrier frequency of a modulated signal to a specified frequency. The analog TV channels and
digitally modulated carriers then pass through the RF combiner.
The signals are broadcast from the headend through optical transmitters typically to fiber nodes in the
network. Amplifiers, coaxial cable, and taps carry the signals to the subscriber premises. Signals are
processed as follows:
• Set-top boxes (STBs), televisions, or VCRs receive analog and digital data signals.
• DOCSIS-based cable interfaces and STBs connected to customer premises equipment (CPE) receive
digital data signals:
1-6
–
Two-way cable interfaces transmit RF signals back through amplifiers to optical fiber receivers
at the headend. These receivers pass the upstream signal to the upstream ports on the
Cisco uBR7225VXR router for processing.
Telco return cable interfaces transmit over the PSTN. Dial-up servers and other equipment
handle the upstream traffic and pass appropriate data to the Cisco uBR7225VXR routers. For
telco return specifics, refer to the “Telco Return” section on page 1-9.
Figure 1-4 shows the architecture of a typical two-way hybrid fiber-coaxial (HFC) network, equipped to
support two-way data communication.
Figure 1-4Two-Way HFC Cable Network Example
Supported System Configurations Overview
OL-17309-02
Cisco provides a configuration tool—Cisco Network Registrar (CNR)—which is optimized for high
performance automatic dynamic IP address allocation to cable interfaces, PCs, and other devices on the
broadband network. Cisco also provides an integrated suite of configuration tools, including CNR, for
relatively large cable networks called Cisco Subscriber Registration Center (CSRC). CSRC allows
large-scale configuration and management of broadband modems. Leveraging the extensibility of CNR,
CSRC enables and administers subscriber self-registration. The directory-enabled architecture of CSRC
allows it to integrate with Lightweight Directory Access Protocol (LDAP) version 3 directory servers.
For more information on CSRC and CNR involvement in the cable network, refer to the CSRC and CNR
documentation.
Cisco Network Registrar Install and Upgrade Guide at the following URL:
The Cisco uBR7225VXR router supports VPN services. Figure 1-5 shows a typical VPN architecture.
VPNs can be initiated at a cable modem residing at a subscriber site or can be initiated by the CMTS at
the headend or distribution hub depending upon your particular Cisco IOS software image.
Figure 1-5Two-Way VPN Network Example
Chapter 1 Cisco uBR7225VXR Overview
NoteMany VPN architectures involve the use of encryption and decryption. Encryption and decryption are
subject to export licensing controls. For more information, refer to Regulatory Compliance and Safety
Information for Cisco uBR7200 Series Universal Broadband Routers, at the following URL:
The Cisco uBR7225VXR router supports the transmission of packetized voice and facsimile traffic over
the cable and IP backbone network. Figure 1-6 on page 1-9 shows a typical two-way configuration
involving Voice-over-IP (VoIP) telephony services.
In telco return configurations, the Cisco uBR7225VXR universal broadband router provides downstream
data flow from cable interface line cards connected to the cable system and accepts upstream traffic via
a combination of the local PSTN and IP network path that terminates at the Cisco uBR7225VXR router.
Upstream data transmission takes place over a telephone modem (external or internal to a
cable interface, as well as a cable interface line card in a PC, based on the third-party cable interface
vendor) connected to an analog telephone line. Figure 1-7 on page 1-10 illustrates a telco return
configuration.
Most Cisco uBR7225VXR universal broadband router components are field-replaceable units (FRUs).
These units, unless otherwise noted, are OIR compatible. See the “Online Insertion and Removal”
section on page 5-1
FRU documentation (instructions on installing, removing, and replacing) is located at the following
URL:
The network processing engine (NPE) maintains and executes the system management functions for the
Cisco uBR7225VXR router. The network processing engine performs the following system management
functions:
• Providing Simple Network Management Protocol (SNMP) management and console/Telnet
interface
• Accounting and switching of data traffic
• Booting and reloading images
Refer to Network Processing Engine and Network Services Engine Installation and Configuration, for
specifications, and removal and replacement instructions for these components. View the document
online at the following URL:
A CPU reset button is located on the NPEs’ faceplate. The CPU reset button resets the entire system.
CautionTo prevent system errors and problems, use the CPU reset button only at the direction of your service
representative.
Hardware Component Descriptions
NPE Comparisons
NoteThe Cisco uBR7200-NPE-G1 should use the boothelper image ubr7200-kboot-mz.122-33.SCA.bin
The network processing engines used in the Cisco uBR7225VXR router are the Cisco uBR7200-NPE-G1
and Cisco uBR7200-NPE-G2.
available from Cisco IOS Release 12.3(33)SCA and later. The Cisco uBR7200-NPE-G2 should use the
boothelper image ubr7200p-boot-mz.122-33.SCA1.bin available from Cisco IOS Release 12.3(33)SCB
and later.
NPE components:
• Reduced instruction set computing (RISC) microprocessor:
–
Cisco uBR7200-NPE-G1 with a 700-MHz Broadcom BCM1250 processor
–
Cisco uBR7200-NPE-G2 with a 1.67-GHz Motorola Freescale MPC7448 processor
• System controller:
–
Cisco uBR7200-NPE-G1 and Cisco uBR7200-NPE-G2 do not require an I/O controller.
• Upgradable memory modules:
–
Cisco uBR7200-NPE-G1—SDRAM: 256 MB (default), 512 MB, and 1 GB. There are two
DRAM memory slots, so 256 MB of memory consists of two 128-MB memory SODIMMs, 512
MB consists of two 256-MB memory SODIMMs, and 1 GB consists of two 512-MB memory
SODIMMs. It is necessary to have the same size SODIMM in each memory bank on an
NPE-G1. The type of DRAM memory being used on the NPE-G1 is double data-rate (DDR)
memory. DDR memory provides high-performance memory access rates.
• Two environmental sensors for monitoring the cooling air as it leaves the chassis.
• Boot ROM for storing sufficient code for booting the Cisco IOS software.
For memory replacement instructions, refer to the Memory Replacement Instructions for the Network
Processing Engine or Network Services Engine and Input/Output Controller document at the following
Cisco uBR7200-NPE-G2—SDRAM: 1 GB (default) and 2 GB. There are two DRAM memory
slots, so 1 GB of memory consists of two 512-MB memory SODIMMs, and 2 GB consists of
two 1 GB memory SODIMMs. It is necessary to have the same size SODIMM in each memory
bank on an NPE-G2. The type of DRAM memory being used on the NPE-G2 is double data-rate
(DDR) memory. DDR memory provides high-performance memory access rates.
Cisco uBR7200-NPE-G1—16-MB packet memory on 256-MB SDRAM, and 32-MB packet
memory on 512-MB and 1-GB SDRAM.
Cisco uBR7200-NPE-G2—32-MB packet memory on 512-MB and 1-GB SDRAM.
Cisco Cable Interface Line Cards
Cisco cable interface line cards (also known as line cards), with internal IF-to-RF upconverters, serve as
the RF interface between the cable headend and both DOCSIS-based cable modems and
EuroDOCSIS-based cable modems and set-top boxes (STBs). Cisco cable interface line cards separate
downstream output and upstream input cable interfaces on the Cisco uBR7225VXR router to enable
downstream and upstream signal combining and splitting arrangements.
Cisco cable interface line cards can be used in both 6-MHz NTSC standard and 8-MHz PAL/SECAM
channel environments.
The cable interface line cards connect directly to the universal broadband router’s midplane. Cable
interface line cards installed in the Cisco uBR7225VXR router support OIR.
CautionTo ensure the proper flow of cooling air across internal components, make sure that blank cable interface
line card is installed in an unoccupied chassis slot. Also make sure that power supply filler plates are
installed in unoccupied power supply bays.
For more information regarding specific cable interface line cards, refer to the Cisco uBR7200 Series Cable Interface Line Card Hardware Installation Guide. To view the document online, go to the
following URL:
http://www.cisco.com/en/US/docs/interfaces_modules/cable/line_cards/installation/guide/mcxxfru.htm
l
The Cisco uBR7225VXR router is equipped with one of the following power supplies:
• 300W AC-input power supply—The maximum AC-input power with single or dual power supply
configuration is 300W. The minimum Cisco IOS Release supported on this power supply is the
Cisco IOS Release 12.2(33)SCA.
• 540W AC-input power supply—The maximum AC-input power with single or dual power supply
configuration is less than 700W. The minimum Cisco IOS Release supported on this power supply
is the Cisco IOS Release 12.2(33)SCD.
NoteEnsure that you do not use a combination of these power supplies in the Cisco uBR7225VXR router.
The power supply contains a main power switch, Input OK and Output OK LEDs, AC-input power
receptacle, and a two-hole grounding lug for the AC-input power supply. The grounding lug at the
rear-bottom portion of the chassis provides a ground connection for electrostatic discharge (ESD)
equipment.
The Cisco uBR7225VXR router supports an optional, second power supply for load-sharing and power
redundancy. If you purchased a Cisco uBR7225VXR router and you want to install a second power
supply, you must order the second power supply separately.
A handle on the AC-input power supply unit provides a grip point for removing and replacing the power
supply. (Figure 1-8 on page 1-14 shows the faceplate of the AC-input power supply.)
Hardware Component Descriptions
A single captive installation screw secures the power supply to the chassis and seats the power supply in
the router midplane. The AC-input power supply has a receptacle for an AC-input power cable. A
modular power cable connects the AC-input power supply to the site AC power source.
Detailed instructions for handling and replacing the Cisco uBR7225VXR universal broadband router
power supply is available in Cisco uBR7200 Series Universal Broadband Router AC Power Supply Replacement Instructions.
This document is available on Cisco.com at the following URL:
CautionTo ensure adequate airflow across the Cisco uBR7225VXR power supplies, a power supply or a power
supply filler plate (with its attached air dam) must be installed in each power supply bay.
NoteSee Appendix A, “Cisco uBR7225VXR Router Specifications,” for AC-input power supply system
power specifications, including input voltage and operating frequency ranges.
The Cisco uBR7225VXR power supply shuts itself down when the input AC voltage, the output DC
voltage, or the internal temperature of the chassis exceeds allowable tolerances. When this occurs, one
or both of the power supply front panel LEDs will turn red. The Cisco uBR7225VXR power supply must
then be reset by manually switching the power switch off and then back on to allow the router to recover.
CautionWhen the input power to Cisco uBR7225VXR power supply is disconnected or lost, the power supply
enters a reset cycle for 10 seconds. Wait at least 10 seconds or move the power switch from one position
to the other to restart the power supply. For example, if the power supply was on when the power was
disconnected or lost, move the power switch to the off position and then back to the on position. If you
do not wait the full 10 seconds or move the power switch from one position to the other, the power supply
does not restart.
Fan Trays
The fan tray for the Cisco uBR7225VXR router, shown in Figure 1-9, consisting of three fans that are
attached to a metal tray, is located on the left side of the chassis (when viewing the router from the front)
and receives 12 VDC through a DC power harness that connects directly to the router midplane.
Temperature sensors on the network processing engine monitor the internal air temperature and send
warning messages when the internal air temperature approaches a specified threshold. If the internal
temperature exceeds the specified threshold, the system environmental monitor shuts down all internal
power to prevent equipment damage from excessive heat.
NoteThe Cisco uBR7225VXR router fan tray is not a field-replaceable unit.
Figure 1-9Cisco uBR7225VXR Fan Tray
Hardware Component Descriptions
270537
The fan tray draws cooling air in through the intake vent on the right side of the chassis (when viewing
the router from the front) and moves the air across the internal components and sends it out through the
exhaust vent on the left side of the chassis. Figure 1-10 shows the airflow through the router.
The left and right sides of the chassis must remain unobstructed to ensure adequate airflow and prevent
overheating inside the chassis; we recommend at least 3 inches of clearance. (See the “Site
The front of the chassis has two slots for cable interface line cards and one bay for the subchassis. See
Figure 1-11.
Figure 1-11Cisco uBR7225VXR Chassis
Hardware Component Descriptions
Subchassis and midplane bay (at rear)
1
Cable interface line card slots
2
Subchassis and Midplane
The subchassis and midplane provide these functions for the Cisco uBR7225VXR router:
• Distributes power from the power supply.
• Bridges the peripheral component interconnect (PCI) buses from the cable interface line cards to the
Cisco uBR7200-NPE-G1 or the Cisco uBR7200-NPE-G2.
• Arbitrates traffic across the PCI buses.
Cisco uBR7225VXR Subchassis
The subchassis (the rear of the router) has two bays for power supplies and one slot for a network
processing engine. (See Figure 1-12.) The cable interface card side of the Cisco uBR7225VXR router
midplane has two connectors for cable interface line cards.
The power supply side of the midplane has two connectors for power supplies and one connector for a
network processing engine. The midplane supplies DC power to the router’s internal components.
Refer to the Cisco uBR7200 Series Universal Broadband Router Subchassis and Midplane Replacement Instructions at the following URL:
Figure 1-12Cisco uBR7225VXR Subchassis and Midplane
7
Chapter 1 Cisco uBR7225VXR Overview
1
To p
2
3
Back
Midplane
1
Fan tray slot
2
Power supply bays
3
Fan tray slot
4
CompactFlash Disk
The Cisco uBR7225VXR universal broadband router has one CompactFlash Disk slot that uses
CompactFlash Disks. The device in this slot is always addressed as disk2: when using Cisco IOS
command-line interface (CLI) commands.
CompactFlash Disks are smaller in size than Type 2 Flash Disks but provide the same AT Attachment
(ATA) interface and equivalent functionality. This interface complies with the ANSI ATA Interface
Document X3T13.1153 D Rev. 9 specification. The CompactFlash Disk provides 512 MB or 1 GB of
storage space.
The CompactFlash Disk has controller circuitry that allows it to emulate a hard disk and automatically
maps out bad blocks and performs automatic block erasure. The CompactFlash Disk also provides the
capability to allocate noncontiguous sectors, which eliminates the need for the squeeze command (which
was required with older-style linear flash memory cards to recover the space used by deleted files).
The CompactFlash Disk also supports the Cisco IOS File System feature, which provides a single
interface to all of the router’s file systems, including the Flash Disks and flash memory, as well as
network file systems such as File Transfer Protocol (FTP) and Trivial FTP (TFTP) servers.
NoteAll CompactFlash Disks must be formatted before their initial use. CompactFlash Disks shipped with
the NPE-G2 are formatted at the factory, but spare memory cards are not formatted.
Preparing the Cisco uBR7225VXR Router for
Installation
This chapter describes the site requirements for installing the Cisco uBR7225VXR universal broadband
router and contains the following sections:
• Safety Recommendations, page 2-1
• Site Requirements, page 2-5
• Required Network Information, page 2-7
• Installation Tools, page 2-8
• Rack-Mount and Cable-Management Kit, page 2-8
• Equipment Required to Verify Your Plant’s RF Setup, page 2-9
• Shipping Container Contents, page 2-9
• Provisioning the Cable Headend, page 2-10
• Site Preparation Checklist, page 2-17
• Component Checklists, page 2-18
Safety Recommendations
The following safety guidelines will help to ensure your safety and protect the equipment. This list does
not cover all potentially hazardous situations, so be alert. Before installing, configuring, or maintaining
the Cisco uBR7225VXR router, review the safety warnings listed in the Regulatory Compliance and Safety Information for Cisco uBR7200 Series Universal Broadband Routers at the following URL:
Chapter 2 Preparing the Cisco uBR7225VXR Router for Installation
• Do not wear loose clothing, jewelry (including rings and chains), or other items that could get caught
in the chassis.
• For systems with installed AC-input power supplies, the Cisco uBR7225VXR router ships with a
3-wire electrical grounding-type plug, which only fits into a grounding-type power outlet. This is a
safety feature. The equipment grounding should be in accordance with local and national electrical
codes.
• The Cisco uBR7225VXR router operates safely when it is used in accordance with its marked
electrical ratings and product usage instructions.
Warning
NoteFor Australia and New Zealand, equipment is to be installed and maintained by service personnel only
Only trained and qualified personnel should be allowed to install or replace this equipment.
Statement 1030
as defined by AS/NZS 3260 Clause 1.2.14.3 Service Personnel.
Warning
Ultimate disposal of this product should be handled according to all national laws and regulations.
Statement 1040
Lifting the Cisco uBR7225VXR Router Safely
Before you install the router, ensure that your site configuration is properly designed and prepared so
that you can avoid having to move the router later to accommodate power sources and network
connections.
A fully-configured Cisco uBR7225VXR router (with two 300W power supplies) weighs approximately
48 pounds (21.8 kilograms).
Whenever you lift a chassis or any heavy object, follow these guidelines:
• Always disconnect all external cables before lifting or moving the chassis.
2-2
• Do not attempt to lift the chassis by yourself; have someone assist you (see Figure 2-1 on page 2-3).
• Ensure that your footing is solid, and balance the weight of the object between your feet.
• Lift the chassis slowly; never move suddenly or twist your body as you lift.
• Keep your back straight and lift with your legs, not your back. If you must bend down to lift the
chassis, bend at the knees, not at the waist, to reduce the strain on your lower back muscles.
• Lift the chassis from the bottom; grasp the underside of the chassis exterior with both hands.
Chapter 2 Preparing the Cisco uBR7225VXR Router for Installation
Figure 2-1Lifting the Chassis (Cisco uBR7246 Router Shown)
Safety Recommendations
271656
Warning
Two people are required to lift the chassis. Grasp the chassis underneath the lower edge and lift with
both hands. To prevent injury, keep your back straight and lift with your legs, not your back. To prevent
damage to the chassis and components, never attempt to lift the chassis with the handles on the
power supplies or on the interface processors, or by the plastic panels on the front of the chassis.
These handles were not designed to support the weight of the chassis.
Safety with Electricity
Follow these basic guidelines when working with any electrical equipment:
• Before beginning any procedures requiring access to the chassis interior, locate the emergency
power-off switch for the room in which you are working.
• Carefully examine your work area for possible hazards such as moist floors, ungrounded power
extension cables, and missing safety grounds.
• Disconnect all power and external cables before installing or removing a chassis.
• Never assume that power has been disconnected from a circuit; always check.
• Do not perform any action that creates a potential hazard to people or makes the equipment unsafe.
• Do not work alone if potentially hazardous conditions exist.
• Never install equipment that appears damaged.
Statement 5
OL-17309-02
CautionYo u must power down the system before removing or replacing the network processing engine. The cable
interface line cards and redundant power supplies are designed to be removed and replaced while the
system is operating, without presenting an electrical hazard or damage to the system.
Chapter 2 Preparing the Cisco uBR7225VXR Router for Installation
Warning
Warning
Warning
The telecommunications lines must be disconnected 1) before unplugging the main power connector
and/or 2) while the housing is open.
Before working on a chassis or working near power supplies, unplug the power cord on AC units;
disconnect the power at the circuit breaker on DC units.
Do not work on the system or connect or disconnect cables during periods of lightning activity.
Statement 1001
Statement 89
In addition, use the guidelines that follow when working with any equipment that is disconnected from
a power source, but still connected to telephone wiring or other network cabling:
• Never install telephone wiring during a lightning storm.
• Never install telephone jacks in wet locations unless the jack is specifically designed for wet
locations.
• Never touch uninsulated telephone wires or terminals unless the telephone line has been
disconnected at the network interface.
• Use caution when installing or modifying telephone lines.
Preventing Electrostatic Discharge Damage
Statement 246
Electrostatic discharge (ESD) damage, which occurs when electronic cards or components are
improperly handled, can result in complete or intermittent system failures. The network processing
engine and cable interface line cards consist of a printed circuit board that is fixed in a metal carrier.
Electromagnetic interference (EMI) shielding, connectors, and a handle are integral components of the
carrier. Although the carrier helps protect the boards, use an antistatic strap whenever handling the
network processing engine and cable interface cards. Handle the carriers by the handles and the carrier
edges only; never touch the boards or connector pins.
CautionAlways tighten the captive installation screws on the network processing engine and cable interface line
cards. These screws prevent accidental removal, provide proper grounding for the system, and help
ensure that the bus connectors are properly seated in the midplane.
Following are guidelines for preventing ESD damage:
• Always use an ESD wrist strap or ankle strap and ensure that it makes good skin contact.
• When handling a removed network processing engine or cable interface line card, make sure that the
equipment end of your ESD strap is attached to an unfinished chassis surface of the router; do not
touch the printed circuit board, and avoid contact between the printed circuit board and your
clothing. Always place the network processing engine or cable interface line card component side
up on an antistatic surface or in a static shielding bag. If you are returning the item to the factory,
immediately place it in a static shielding bag.
Chapter 2 Preparing the Cisco uBR7225VXR Router for Installation
• Ensure that the network processing engine is fully inserted in its chassis slot and the captive
installation screws are tightened. The captive installation screws prevent accidental removal,
provide proper grounding for the system, and help ensure that the bus connectors are seated in the
midplane.
• Ensure that each cable interface line card is fully inserted in its chassis slot and that its captive
installation screws are tightened.
CautionFor safety, periodically check the resistance value of the antistatic strap. The measurement should be
between 1 and 10 megohms.
Site Requirements
To ensure normal operation and avoid unnecessary maintenance, plan your site configuration and
prepare your site before installation. Take into account the following criteria:
• Verify that your cable network meets system requirements and DOCSIS or EuroDOCSIS
downstream and upstream specifications.
• Select forward and reverse channel frequencies from the range specified in your channel plan.
• Make sure that the site maintains an ambient temperature of 32 to 104
area around the chassis as free from dust as is practical.
Site Requirements
o
F (0 to 40oC), and keep the
NoteTo locate the most reliable channels for your downstream and upstream channel plans, we recommend
that you perform a sweep of all available channels for at least a 24-hour period to verify the presence or
absence of impulse or ingress noise.
AC Power
The AC-input power supply uses a power factor corrector that allows the Cisco uBR7225VXR router to
operate on input voltage and frequency within the ranges of 100 to 240 VAC and 50/60 Hz.
NoteWe recommend an uninterruptable power source to protect against power failures at your site. For the
Cisco uBR7225VXR router, the 300W AC-input power supply has an electrical input current rating of
4A with 100Vac input and the 540W AC-input power supply has an electrical input current rating of 6.5A
with 100Vac input.
See Appendix A, “Cisco uBR7225VXR Router Specifications,” for system power specifications,
including input voltage and operating frequency ranges.
Site Environment
Table 2-1 lists the operating and nonoperating environmental site requirements. The following ranges
are those within which the Cisco uBR7225VXR router continues to operate; however, a measurement
that is approaching the minimum or maximum of a range indicates a potential problem. You can maintain
normal operation by anticipating and correcting environmental anomalies before they approach the
minimum or maximum of an operating range.
Chapter 2 Preparing the Cisco uBR7225VXR Router for Installation
Site Requirements
To provide airflow through the Cisco uBR7225VXR router, cooling air is drawn in through the air intake
vent on the right side of the chassis (when viewing the router from the front) and is exhausted through
the left side of the chassis. Keep the right and left sides of the chassis clear of obstructions and away
from the exhaust of other equipment.
NoteThe Cisco uBR7225VXR router is suitable for installation in Network Telecommunication Facilities and
locations where the National Electrical Code (NEC) applies. The Cisco uBR7225VXR router is not
intended for installation in outside plant (OSP) locations.
Table 2-1Specifications for Operating and Nonoperating Environments
Humidity, ambient (noncondensing) nonoperating
and storage
Altitude, operating and nonoperatingSea level10,000 feet (3,050 meters)
Vibration, operating 5 to 200 Hz, 0.5 g (1 oct./min.)–
Vibration, nonoperating 5 to 200 Hz, 1 g (1 oct./min.)
o
F (0oC) 104oF (40oC)
o
F (–20oC) 149oF (65oC)
5% 95%
–
200 to 500 Hz, 2 g (1 oct./min.)
Site Configuration: Maintaining Normal Operation
Planning a proper location for the Cisco uBR7225VXR universal broadband router and the layout of
your equipment rack or wiring closet are essential for successful system operation. Equipment placed
too close together or inadequately ventilated can cause system overtemperature conditions. In addition,
chassis panels made inaccessible by poor equipment placement can make system maintenance difficult.
Following are precautions that can help avoid problems during installation and ongoing operation.
General Precautions
Follow these general precautions when planning your equipment locations and connections:
• Use the show environment command regularly to check the internal system status. The
environmental monitor continually checks the interior chassis environment; it provides warnings for
high temperature and maximum and minimum voltages and creates reports on any occurrences. If
warning messages are displayed, take immediate action to identify the cause and correct the
problem.
• We recommend keeping the Cisco uBR7225VXR router off the floor and out of any area that tends
to collect dust, excessive condensation, or water.
• Follow ESD prevention procedures to avoid damage to equipment. Damage from static discharge
can cause immediate or intermittent equipment failure.
Chapter 2 Preparing the Cisco uBR7225VXR Router for Installation
• Ensure that the network processing engine, cable interface line cards, any blank cable interface line
cards, power supplies, and any power supply filler plates are in place and secure. The fans direct
cooling air throughout the chassis interior; a loose component or empty slot can redirect the airflow
away from active components and cause overheating.
Power Considerations
Follow these precautions and recommendations when planning power connections to the
Cisco uBR7225VXR router:
• Check the power at your site before installation and periodically after installation to ensure that you
are receiving clean power. Install a power conditioner and appropriate surge suppression if
necessary.
• Install proper grounding to avoid damage from lightning and power surges.
Required Network Information
Required Network Information
After you install the chassis, your system administrator must configure the individual and system
interfaces before you connect your system to external networks. Refer to the following documentation
for configuration information.
Cisco uBR7200 Series Software Configuration Guide at the following URL:
• IP addresses and subnet masks, if you are routing IP.
• Dial-up access telephone numbers, usernames, and passwords for telco return operation.
• RADIUS security and accounting configuration.
• Gateway and gatekeeper zone configuration for your H.323 VoIP network.
• Gateway and call-agent configuration for your SGCP VoIP network.
• Zone names, network numbers, or node numbers for the new interfaces, if required.
• Operating speeds for specific interfaces—For example, serial interfaces operate at speeds of up to
2 Mbps. The speed of an interface often depends on the speed of the remote device to which it is
attached.
Installation Tools
Your Cisco uBR7225VXR universal broadband router chassis is fully assembled at the factory; no
assembly is required. However you will need the following tools and equipment to install the chassis and
the rack-mount and cable-management kit:
Chapter 2 Preparing the Cisco uBR7225VXR Router for Installation
• Number 2 Phillips screwdriver
• 3/16-inch flat-blade screwdriver
• 7/16-inch flat-blade screwdriver
• 7/16-inch torque wrench for connecting coaxial cables to the cable F-connectors on the
cable interface line cards—Recommended torque is 20 inch-pounds (optional)
• Tape measure (optional)
• Level (optional)
Rack-Mount and Cable-Management Kit
The rack-mount and cable-management kit includes the following parts:
• Two rack-mount brackets for mounting the chassis in the rack.
• Cable-management bracket to relieve the strain on installed cable interface line card interface
cables.
• Eight M4 x 6-mm Phillips flathead screws to secure the rack-mount brackets to the chassis.
• Four M3 x 6-mm Phillips panhead screws to secure the cable-management bracket to the chassis.
• Four 10/32 x 3/8-inch slotted binderhead screws to secure the rack-mount brackets to the rack rails.
For more information on the rack-mount brackets and cable-management bracket, refer to the
“Cisco uBR7225VXR Router Chassis Rack-Mounting Options” section on page 3-2.
Chapter 2 Preparing the Cisco uBR7225VXR Router for Installation
Equipment Required to Verify Your Plant’s RF Setup
Equipment Required to Verify Your Plant’s RF Setup
To verify your plant’s RF setup, you need the following:
• RF spectrum analyzer
• For coaxial cabling:
–
Diplex filters/splitters
–
Coaxial cable crimping tool
–
New coaxial cable
–
Coaxial jumpers that are at least 2 to 3 feet long (maximum of 5 feet)
• For fiber networks, optical receivers for each upstream optical path
• Assorted RF attenuators (with at least two 20-dB attenuators)
NoteFor headend RF and data setups, refer to Chapter 4, “Connecting the Cisco uBR7225VXR Router to the
Cable Headend.” Refer to Appendix F, “Manufacturers for Headend Provisioning Requirements,” for a
list of manufacturers. Refer to Appendix C, “Cable Specifications,” for coaxial cabling specifications.
In addition, you might need the following:
• Crossover Ethernet cable with RJ-45 connectors—If you plan to connect a computer directly to an
Ethernet port in the Cisco uBR7225VXR router, you need this type of cable.
• Fast Ethernet transceiver.
• DOCSIS cable modem or DOCSIS-based STB and CPE devices to test full system functionality.
NoteWhen the Cisco uBR7225VXR router starts running, IF downstream output is generated. For more
information, see the “Powering On the Cisco uBR7225VXR Router” section on page 3-18.
Shipping Container Contents
When you receive your Cisco uBR7225VXR universal broadband router, use the following procedure to
check the contents of the shipping container. Use the Cisco uBR7225VXR Router Installation Checklist
or the “Component Checklists” section on page 2-18 to ensure you received all the components that you
ordered.
NoteDo not discard the shipping container. You will need the container if you move or ship your
Cisco uBR7225VXR router in the future.
Verifying the Shipping Container Contents
Step 1Verify that the following are included in the shipping container (the accessories box might be separate):
• One Cisco uBR7225VXR universal broadband router chassis containing all of the components you
ordered for your system (except the rack-mount and cable-management kit)
Chapter 2 Preparing the Cisco uBR7225VXR Router for Installation
NoteFor a VoIP system using H.323, ensure that the CMTS has been properly provisioned with equipment
such as VoIP gateways and gatekeepers. For SGCP-based VoIP systems, ensure that the CMTS has been
properly provisioned with equipment such as VoIP gateways and call-agents.
Headend Certification
The cable headend plant must pass both analog and digital certification:
• In the United States, the Federal Communications Commission (FCC) mandates minimum technical
performance requirements for cable systems.
• For international requirements, consult with local agencies for certification requirements.
The digital certification process is described in Chapter 4, “Connecting the Cisco uBR7225VXR Router
to the Cable Headend.”
Diplex Filters
Provisioning the Cable Headend
For coaxial cabling, diplex filters must be installed in the RF path between the cable interface cards in
the Cisco uBR7225VXR universal broadband router and cable interfaces and STBs. Diplex filters
separate the downstream signals from the upstream signals.
NoteFor fiber optics, laser transmitters and optical receivers handle the frequency separation of upstream and
downstream. Refer to the “Receivers” section on page 2-11.
High-frequency signals flow in the downstream direction from the Cisco uBR7225VXR router to
cable interfaces and STBs. Low-frequency signals flow in the upstream direction from the
cable interfaces to the Cisco uBR7225VXR router.
A diplex filter has three ports: low, high, and common. The downstream attaches to the high port because
it runs at high frequency. The upstream attaches to the low port because it runs at a low frequency. The
common port attaches to a splitter attached to one or more cable interfaces and STBs.
In two-way cable networks, the diplex filter takes the upstream and downstream and combines them on
one cable for the cable interface. The downstream output signal from the Cisco uBR7225VXR router
runs through the upconverter and then enters the high filter port of the diplex filter. The signal exits the
common port of the filter and is distributed to the cable interfaces. The upstream signal from the cable
modem enters the common port of the diplex filter and flows to the upstream receive ports of the
Cisco uBR7225VXR cable interface line cards through the diplex filters’ low port.
NoteAppendix F, “Manufacturers for Headend Provisioning Requirements,” provides a list of diplex filter
manufacturers and websites for more information.
Receivers
OL-17309-02
If the upstream channels of your cable plant terminate at the headend over fiber-optic lines, ensure that
you have a receiver allocated for each upstream in your network.
A DHCP server must be installed at the headend. The DHCP server must also offer a time-of-day (TD)
server option that is compliant with RFC 868.
In conjunction with the DHCP server, a Domain Name System (DNS) server must be installed to
translate names of network nodes into IP addresses. A TFTP server must be installed to facilitate the
transfer of DOCSIS configuration files over the broadband network.
Cisco provides a configuration tool with every Cisco uBR7225VXR universal broadband
router—Cisco Network Registrar (CNR)—to automate dynamic IP address allocation to
cable interfaces, PCs, and other devices on the broadband network. CNR provides integrated DHCP and
DNS services for your network configuration.
Telco Return
To support telco return, ensure that:
• Your downstream plant meets DOCSIS or EuroDOCSIS specifications.
Chapter 2 Preparing the Cisco uBR7225VXR Router for Installation
• Your headend is wired for narrowcast downstream data transmission.
• You have assigned downstream frequencies.
• All equipment needed to support upstream traffic over the PSTN, as well as to monitor telco return
service features is installed. Key components include:
–
Dial-up access server (for example, the Cisco AS5300 or Cisco AS5800)
–
RADIUS dial security server
• All third-party, telco return cable interfaces are DOCSIS-compliant.
• Your Cisco IOS software image supports telco return functionality.
The following sections describe CMTS equipment necessary to support telco return service.
Dial-Up/Remote Access Servers
Because a telco return cable network relies on the local telephone system to complete the upstream data
path to the Cisco uBR7225VXR router, you need to be sure that you provision your network with a
dial-up access server and other required equipment through which remote cable interfaces will gain
access to your headend.
RADIUS Dial Security Servers
After remote telco return cable interfaces have initiated dial-up to the CMTS via the network access
server, a RADIUS dial security server typically authenticates their respective usernames and passwords
or MAC address and passwords and then determines whether or not to allow the connection.
In addition to the dial-up numbers provided in telephony channel descriptor (TCD) messages originating
from the Cisco uBR7225VXR router, username and password information is included in TCD messages
to validate the cable interface’s upstream connection. After dialing in to the network access server, the
username and password portions of the TCD messages are passed through a RADIUS dial access server
for authentication before the upstream data path can be completed. (See Figure 2-2.)
Chapter 2 Preparing the Cisco uBR7225VXR Router for Installation
Figure 2-2Servers on an HFC Network
Provisioning the Cable Headend
S
Cisco Network
Registrar
DHCP/DNS server
TFTP
server
*A remote access server is required on an HFC network only
when you want to offer VoIP using H.323 or telco return service.
ecurity
server
(optional)
Log
server
(optional)
Time-of-day
uBR7225VXR
server
Cisco
Remote
access serve
Authentication, Authorization, and Accounting Servers
Authentication, authorization, and accounting (AAA) servers are essential to the network, because they
typically monitor usage for subscriber billing and record keeping. AAA features call upon a RADIUS
security server to help authenticate and monitor users’ access.
Cisco 7500
r*
series router
Internet
271657
VoIP Gateways and Gatekeepers
To support digitized voice transmission on uBR7225VXR router using Cisco IOS Release 12.2(33)SCA
CMTS images, be sure to include VoIP gateways and gatekeepers in your configuration. Cisco IOS
Release 12.2(33)SCA supports VoIP by using the H.323 protocol. VoIP gateways convert IP-based voice
packets into standard PSTN voice traffic, making the process of placing calls over the IP network
transparent to users.
VoIP gatekeepers manage H.323-compliant gateways throughout the network. Gatekeepers also manage
traffic between their local cable system networks, as well as the networks of other VoIP gatekeepers.
VoIP SGCP Pass-Through
To support digitized voice transmission using Simple Gateway Control Protocol (SGCP), be sure to
include VoIP gateways and external call control elements (often referred to as call-agents) in your
configuration. Cisco IOS Release 12.2(33)SCA and later versions support VoIP communication using
the SGCP 1.1 protocol on uBR7225VXR. Just as with H.323 systems, VoIP gateways in an SGCP
environment convert IP-based voice packets into standard PSTN voice traffic, making the process of
placing calls over the IP network transparent to users.
Call-agents manage SGCP-compliant gateways throughout the network, allowing them to engage in
common channel signaling (CCS) over a 64-kbps circuit emulation service (CES) circuit.
This section provides guidelines for setting up the headend wiring and cabling at your site. When
planning the location of the new system, consider the distance limitations for signaling, EMI, and
connector compatibility, as described in the following sections.
Interference Considerations
When wires are run for any significant distance in an electromagnetic field, interference can occur
between the field and the signals on the wires. This fact has two implications for the construction of
headend wiring:
• Bad wiring practice can result in radio interference emanating from the wiring, ingress noise,
co-channel interference, and degraded or erratic universal broadband router performance.
• Strong EMI, especially when caused by lightning or radio transmitters, can destroy the signal drivers
and receivers in the Cisco uBR7225VXR router, and can even create an electrical hazard by
conducting power surges through lines and into equipment. (Review the safety warnings in the
“Safety with Electricity” section on page 2-3.)
If you use twisted-pair cable in your headend wiring with a good distribution of grounding conductors,
the wiring is unlikely to emit radio interference. If you exceed the recommended distances, use a
high-quality twisted-pair cable with one ground conductor for each data signal when applicable.
If wires exceed recommended distances, or if wires pass between buildings, give special consideration
to the effect of a lightning strike in your vicinity. The electromagnetic pulse caused by lightning or other
high-energy phenomena can easily couple enough energy into unshielded conductors to destroy
electronic devices. If you have had EMI problems in the past, you might want to consult experts in
electrical surge suppression and shielding.
Chapter 2 Preparing the Cisco uBR7225VXR Router for Installation
Distance Limitations and Interface Specifications
The size of your networks and the distances between connections depend on the type of signal, the signal
speed, and the transmission media (the type of cabling used to transmit the signals). For example,
standard coaxial cable has a greater channel capacity than twisted-pair cabling. The distance and rate
limits are the IEEE-recommended maximum speeds and distances for signaling; however, you can
usually get good results at speeds and distances far greater than these. For example, the recommended
maximum rate for V.35 is 2 Mbps, and it is commonly used at 4 Mbps without any problems. If you
understand the electrical problems that might arise and can compensate for them, you should get good
results with rates and distances greater than those recommended by IEEE; however, do so at your own
risk.
NoteWe recommend that you do not exceed specified transmission rate and distance limits.
When preparing your site for network connections to the Cisco uBR7225VXR router, you must consider
a number of factors related to each type of interface:
• The type of cabling required for each type of interface (fiber, thick or thin coaxial, shielded
twisted-pair, or unshielded twisted-pair cabling)
• Distance limitations for each signal type
• The specific cables you need to connect each interface
Chapter 2 Preparing the Cisco uBR7225VXR Router for Installation
• Any additional interface equipment you need, such as transceivers, hubs, switches, modems,
channel service units (CSUs), or data service units (DSUs)
• Cable pinouts if you plan to build your cables
Before installing the Cisco uBR7225VXR router, have all additional external equipment and cables
available. The information listed above is available at Cisco.com. For ordering information, contact a
customer service representative.
Equipment Racks
The rack-mounting hardware included with the Cisco uBR7225VXR universal broadband router is
suitable for most 19-inch equipment racks and telco-type racks. To easily access field-replaceable units
(FRUs) while the router is installed in a rack, ensure that you have access to the front and rear of the
router.
Before using a particular rack, check for obstructions (such as a power strip) that could impair
rack-mount installation. If a power strip impairs a rear rack-mount installation, remove the power strip
before installing the Cisco uBR7225VXR router in the rack, then replace it after the chassis is installed.
As an alternative, you can mount the Cisco uBR7225VXR router on an equipment shelf if the rack
dimensions allow you to secure the router to the shelf, and the overall configuration permits safe
installation and access. However, we recommend rack-mounting the Cisco uBR7225VXR router.
Figure 2-3 on page 2-16 shows the Cisco uBR7225VXR router footprint and outer dimensions.
When rack-mounting the Cisco uBR7225VXR router, consider the following information:
Provisioning the Cable Headend
• To mount the router between two posts or rails using the brackets, the inner clearance (the width
between the inner sides of the two posts or rails) must be at least 17.5 inches (44.45 cm).
• The height of the Cisco uBR7225VXR chassis is 3.5 inches (8.89 cm).
• When mounting the router in four-post or telco-type racks, be sure to use all the screws and the
brackets provided to secure the chassis to the rack posts.
Figure 2-3Cisco uBR7225VXR Router Footprint and Outer Dimensions (View from Top Looking
Chapter 2 Preparing the Cisco uBR7225VXR Router for Installation
Down)
17.32 in.
23.875 in.
NoteWe recommend the rear bracket mounting system for four-post racks because this method enables you
21.875 in.
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to keep cables from protruding too far out in front of the Cisco uBR7225VXR router, and simultaneously
manage the cables at the front of the chassis with the cable-management bracket.
When planning your rack installation, consider the following information:
• Install the Cisco uBR7225VXR router in an open rack whenever possible. If installation in an
enclosed rack is unavoidable, ensure that the rack has adequate ventilation.
• If you plan to use an equipment shelf, ensure that the shelf is constructed to support the weight and
dimensions of the chassis. Figure 2-3 shows the chassis footprint, which you will need if you are
designing a customized shelf. We recommend that you use the rack-mount kit for the
Cisco uBR7225VXR router (product number ACS-uBR7225-RMK=).
• Allow sufficient clearance around the rack for maintenance. If the rack is mobile, you can push it
back near a wall or cabinet for normal operation and pull it out for maintenance (connecting cables,
or replacing or upgrading components). Otherwise, allow at least 23.25 inches (59.06 cm) of
clearance at the front, and 19 inches (48.3 cm) at the back to remove any of the field-replaceable
units.
• Maintain a minimum clearance of 3 inches (7.72 cm) on the right and left of the chassis for the
cooling air inlet and exhaust ports, respectively. Avoid placing the Cisco uBR7225VXR router in an
overly congested rack or directly next to another equipment rack; otherwise, the heated exhaust air
from other equipment can enter the inlet air vents and cause an overtemperature condition inside the
router.
• Always install heavier equipment in the lower half of a rack to maintain a low center of gravity and
prevent the rack from falling.
2-16
• If you use telco-type racks, be sure that the rack is bolted to the floor and secured, because in these
types of installations, only one end of the chassis mounts to the two rack posts with the brackets.
Ensure that the weight of the chassis does not make the rack unstable.
Chapter 2 Preparing the Cisco uBR7225VXR Router for Installation
• Install and use the cable-management bracket included with the Cisco uBR7225VXR rack-mount
kit to keep cables organized. Consider the equipment and cabling that is already installed in the rack.
Ensure that cables from other equipment will not impair access to the interface slots, or require you
to disconnect cables unnecessarily to perform equipment maintenance or upgrades.
In addition to the preceding guidelines, review the precautions for avoiding overtemperature conditions
in the “Site Environment” section on page 2-5. To properly install the Cisco uBR7225VXR router
chassis in a rack, refer to the instructions in the “Cisco uBR7225VXR Router Chassis Rack-Mounting
Options” section on page 3-2.
Site Preparation Checklist
CautionDo not install the Cisco uBR7225VXR chassis in an enclosed rack or room that is not properly ventilated
or air-conditioned. The Cisco uBR7225VXR chassis overheats if the input air temperature reaches 105
(41oC).
Site Preparation Checklist
Before installing the Cisco uBR7225VXR router, assemble the equipment needed to support your
network configuration and subscriber service offering. Ensure all power and cabling requirements are
met based on the equipment to be installed. Also ensure that environmental conditions are met to
maintain proper equipment operation.
Table 2-2 is a checklist that identifies the key tasks to complete.
Table 2-2Site Preparation Checklist
TaskVerified ByDate
General:
Safety recommendations and guidelines reviewed.
Required general CMTS preparations completed.
Site power voltages verified.
Site environmental specifications verified.
Downstream and upstream channel plans created.
Cable plant balanced, swept and verified to comply with DOCSIS or EuroDOCSIS
recommendations.
Optical receivers adjusted for proper upstream RF output levels.
Required passwords, IP addresses, device names available.
All additional CMTS equipment to support Internet access services, RF-related
equipment, servers and other host computers, a Cisco uBR900 series cable access router,
and console accessory kit to test operation of your network available.
Required tools and cables available.
Telco Return Configurations:
Telco return dial-up plan created.
Network access server installed and configured.
Telephone circuits, connections, and all equipment to support telco return available.
• Installing the Brackets on the Chassis, page 3-7
• Installing the Chassis in a Workbench or Tabletop Environment, page 3-12
• Cabling, page 3-13
• Console and Auxiliary Port Connection Equipment, page 3-14
• Protective Grounding, page 3-16
• Connecting Power, page 3-16
• Powering On the Cisco uBR7225VXR Router, page 3-18
Cisco uBR7225VXR Router Installation Checklist
A rack-mount and cable-management kit is included in the shipping container. The rack-mount brackets
in the kit are for mounting the Cisco uBR7225VXR in standard, 19-inch-wide, 4-post equipment racks
or telco-type equipment racks. The rack-mount brackets are not suitable for use with other racks, such
as 23-inch telco racks. The cable-management bracket is designed to relieve the strain on interface cables
that are installed on cable interface line cards in a Cisco uBR7225VXR router.
If you are installing an equipment shelf or using mounting hardware other than that supplied with the
chassis, review the guidelines in the “Equipment Racks” section on page 2-15, then proceed to the
“Cisco uBR7225VXR Router Chassis Rack-Mounting Options” section on page 3-2.
If you do not plan to install your Cisco uBR7225VXR router in an equipment rack, proceed to the
“Installing the Chassis in a Workbench or Tabletop Environment” section on page 3-12.
To assist you with your installation and to provide a historical record of what was done, and by whom,
use “Cisco uBR7225VXR Router Installation Checklist” section on page 2. Make a copy of this
checklist and indicate when each procedure or verification is completed. When the checklist is
completed, place it in your site log (see Appendix G, “Site Log”) along with the other records for your
new router.
The chassis mounts to two rack posts with brackets that attach to either the front, middle, or rear sides
of the chassis. The inside width between the posts or mounting strips (left and right) must be at least
17.5 inches (44.45 cm).
Some equipment racks provide a power strip along the length of one of the mounting strips. Figure 3-1
shows a typical 4-post equipment rack with a power strip along one of the back posts. If your rack has
this feature, consider the position of the strip when planning fastener points and ensure that you will be
able to pull cable interface line card cables and other FRUs straight out of their respective slots.
The inlet and exhaust ports for cooling air are located on the right and left of the chassis, respectively,
so multiple universal broadband routers can be stacked in a rack with little or no vertical clearance.
NoteWe recommend the rear bracket mounting system for 4-post racks. This method enables you to keep
cables from protruding too far out in front of the Cisco uBR7225VXR router and to simultaneously
manage the cables at the front of the chassis with the cable-management bracket.
Figure 3-4Installing the Chassis in a 4-Post Rack—Chassis Protruding Front Installation
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1
Rack-mount bracket
1
See the “Installing Rack-Mount Brackets in the Middle of the Chassis” section on page 3-9 for bracket
mounting information.
Figure 3-5Installing the Chassis in a Telco-Type Rack
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1
Rack-mount bracket
1
Cable-Management Bracket Requirements
There are two cable-management bracket configurations available for rack-mounting the
Cisco uBR7225VXR router. In the first configuration, for a 4-post rack, the rack-mount brackets are
installed at the rear of the chassis and the cable-management bracket is installed at the right front of the
chassis. (See Figure 3-6.) You must install both sets of brackets before you install the chassis in the rack.
In the second configuration, for a telco-type rack, the rack-mount brackets are installed at the middle of
the chassis and the cable-management bracket is installed at the right front of the chassis. (See
Figure 3-7.) You must install both sets of brackets before you install the chassis in the rack.
Chapter 3 Installing the Cisco uBR7225VXR Router
Figure 3-6Installing the Chassis in a 4-Post Rack with an Installed Cable-Management Bracket
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1
Rack-mount bracket
1
Figure 3-7Installing the Chassis in a Telco-Type Rack with an Installed Cable-Management
This section explains how to install the rack-mount brackets and cable-management bracket on a
Cisco uBR7225VXR universal broadband router. Before installing the chassis in the rack, you must
install cable-management bracket and a rack-mount bracket on each side of the front, middle, or rear of
the chassis.
The parts and tools required for installing the rack-mount and cable-management bracket are listed in
the “Installation Tools” section on page 2-8.
Installing Rack-Mount Brackets on the Rear of the Chassis
To install the rack-mount brackets and cable-management bracket on the chassis for a rear rack-mount
configuration, complete the following steps:
Step 1Locate the threaded holes in the rear sides of the chassis.
Step 2Align the first rack-mount bracket to the threaded holes in the right side of the chassis. See Figure 3-8.
Installing the Brackets on the Chassis
Figure 3-8Installing the Rack-Mount Brackets on the Rear of the Chassis
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1
Rack-mount bracket
1
NoteThere are five holes in each of the rack-mount brackets for the Cisco uBR7225VXR router. Four holes
are used for front and middle mount, and five holes are used for rear mount.
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Step 3Thread five M4 x 6-mm Phillips flathead screws through the rack-mount bracket and into the side of the
chassis. Use a number 2 Phillips screwdriver to tighten the screws.
Step 4Repeat Step 1 through Step 3 for the other rack-mount bracket.
Step 5If you plan to include the cable-management bracket in your rear rack-mount configuration, align the
Step 6Thread two M3 x 6-mm Phillips panhead screws through the cable-management bracket and into the
chassis, and tighten the screws.
This completes the procedure for installing the rack-mount brackets and the cable-management bracket
on the chassis for a rear rack-mount configuration. Proceed to the “Installing the Chassis in the Rack”
section on page 3-10.
CautionTo prevent injury, review the safety precautions in Chapter 2, “Preparing the Cisco uBR7225VXR
Router for Installation,” before installing the Cisco uBR7225VXR router in a rack.
Installing Rack-Mount Brackets on the Front of the Chassis
To install the rack-mount brackets and cable-management bracket on the chassis for a front rack-mount
configuration, complete the following steps:
Step 1Locate the threaded holes in the front sides of the chassis.
Step 2If you want the front of the chassis flush with the front of the rack, align the first rack-mount bracket to
the threaded holes in the right side of the chassis as shown in Figure 3-9 on page 3-8.
If you want the front of the chassis protruding from the rack, align the first rack-mount bracket to the
threaded holes in the right side of the chassis as shown in Figure 3-10 on page 3-9.
NoteThere are five holes in each of the rack-mount brackets for the Cisco uBR7225VXR. Four holes are used
for front and middle mount, and five holes are used for rear mount.
Figure 3-9Installing the Rack-Mount Brackets so the Front of the Chassis Is Flush with the Rack
Figure 3-10Installing the Rack-Mount Brackets so the Front of the Chassis Protrudes Out of the
Rack
Rack-mount bracket
1
Installing the Brackets on the Chassis
Step 3Thread four M4 x 6-mm Phillips flathead screws through the rack-mount bracket and into the side of the
chassis. Use a number 2 Phillips screwdriver to tighten the screws.
Step 4Repeat Step 1 through Step 3 for the other rack-mount bracket.
Step 5If you plan to include the cable-management bracket in your front rack-mount configuration, align the
bracket with the two right front-side holes.
Step 6Thread two M3 x 6-mm Phillips panhead screws through the cable-management bracket and into the
chassis, and tighten the screws.
This completes the procedure for installing the rack-mount brackets on the chassis for a front rack-mount
configuration. Proceed to the “Installing the Chassis in the Rack” section on page 3-10.
CautionTo prevent injury, review the safety precautions in Chapter 2, “Preparing the Cisco uBR7225VXR
Router for Installation,” before installing the universal broadband router in a rack.
Installing Rack-Mount Brackets in the Middle of the Chassis
To install the rack-mount brackets and cable-management bracket at the middle of the chassis for a
telco-type rack-mount configuration, complete the following steps:
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Step 1Locate the threaded holes in the middle sides of the chassis.
Step 2Align the first rack-mount bracket to the threaded holes in the right side of the chassis. See Figure 3-11.
NoteThere are five holes in each of the rack-mount brackets for the Cisco uBR7225VXR router. Four holes
are used for front and middle mount, and five holes are used for rear mount.
Figure 3-11Installing the Rack-Mount Brackets in the Middle of the Chassis for Telco-Type Racks
Rack-mount bracket
1
Chapter 3 Installing the Cisco uBR7225VXR Router
Step 3Thread four M4 x 6-mm Phillips flathead screws through the rack-mount bracket and into the side of the
chassis. Use a number 2 Phillips screwdriver to tighten the screws.
Step 4Repeat Step 1 through Step 3 for the other rack-mount bracket.
Step 5If you plan to include the cable-management bracket in your telco-type rack-mount configuration, align
the bracket with the right front-side holes.
Step 6Thread two M3 x 6-mm Phillips panhead screws through the cable-management bracket and into the
chassis, and tighten the screws.
This completes the procedure for installing the rack-mount brackets and cable-management bracket on
the Cisco uBR7225VXR router. Proceed to the following section, “Installing the Chassis in the Rack.”
CautionTo prevent injury, review the safety precautions in Chapter 2, “Preparing the Cisco uBR7225VXR
Router for Installation,” before installing the Cisco uBR7225VXR router in a rack.
Installing the Chassis in the Rack
After installing the brackets on the chassis, mount the chassis by securing the rack-mount brackets to the
posts or mounting strips in the rack using the slotted screws provided.
3-10
NoteWhen installing the uBR7225VXR in a rack, ensure that paint is removed from the rack and an
anti-oxidant is applied at the contact points to ensure reliable metal to metal contact.
CautionBecause the brackets support the weight of the entire chassis, be sure to use all of the required slotted
screws to fasten the two rack-mount brackets to the rack posts. Figure 3-2 on page 3-4, Figure 3-3 on
page 3-4, Figure 3-4 on page 3-5, and Figure 3-5 on page 3-5 show typical installations in 19-inch,
four-post and telco-type equipment racks.
Installing the Brackets on the Chassis
Warning
Two people are required to lift the chassis. Grasp the chassis underneath the lower edge and lift with
both hands. To prevent injury, keep your back straight and lift with your legs, not your back. To prevent
damage to the chassis and components, never attempt to lift the chassis with the handles on the
power supplies or on the interface processors, or by the plastic panels on the front of the chassis.
Warning
These handles were not designed to support the weight of the chassis.
To prevent bodily injury when mounting or servicing this unit in a rack, you must take special
Statement 5
precautions to ensure that the system remains stable. The following guidelines are provided to
ensure your safety:
• This unit should be mounted at the bottom of the rack if it is the only unit in the rack.
• When mounting this unit in a partially filled rack, load the rack from the bottom to the top with
Statement 1006
the heaviest component at the bottom of the rack.
• If the rack is provided with stabilizing devices, install the stabilizers before mounting or servicing
the unit in the rack.
To install the chassis in the rack, complete the following steps:
Step 1On the chassis, ensure that all captive installation screws on the network processing engine, each
cable interface line card, and each power supply are tightened.
Step 2Make sure that your path to the rack is unobstructed. If the rack is on wheels, ensure that the brakes are
engaged or that the rack is otherwise stabilized.
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CautionTwo people should perform Step 3 through Step 6.
Step 3Position the chassis so that the front end is closest to you; then lift the chassis and move it to the rack.
To prevent injury, avoid sudden twists or moves.
Step 4Slide the chassis into the rack, pushing it back until the brackets (installed at the front or rear of the
chassis) meet the mounting strips or posts on both sides of the equipment rack.
NoteThe rack-mount bracket must be placed behind the rack post or mounting strip in the rear installation
configuration. (See Figure 3-2 on page 3-4.)
Step 5While keeping the brackets flush against the posts or mounting strips, position the router so that the holes
in the brackets are aligned with those in the mounting strips.
Installing the Chassis in a Workbench or Tabletop Environment
Step 6Insert the 10/32 x 3/8 slotted screws (two to a side) through the brackets and into the mounting strip (use
the top and bottom bracket holes, shown in Figure 3-2 on page 3-4, Figure 3-3 on page 3-4, Figure 3-4
on page 3-5, and Figure 3-5 on page 3-5). Using a 7/16-inch flat-blade screwdriver, tighten all the
screws.
This completes the procedure for installing the chassis in the rack. Proceed to the “Cabling” section on
page 3-13 to continue the installation.
Installing the Chassis in a Workbench or Tabletop Environment
The Cisco uBR7225VXR universal broadband router should already be in the area where you will install
it, and your installation location should already be determined. If not, refer to the “Site Requirements”
section on page 2-5.
When installing the router on a workbench or tabletop, ensure that the surface is clean and in a safe
location and that you have considered the following:
• The Cisco uBR7225VXR router requires at least 3 inches (7.72 cm) of clearance at the inlet and
exhaust vents (the right and left sides of the router).
• The Cisco uBR7225VXR router should be installed off the floor. (Dust that accumulates on the floor
can be drawn into the interior of the router by the cooling fans. Excessive dust inside the router can
cause overtemperature conditions and component failures.)
• There must be approximately 23.25 inches (59.06 cm) of clearance at the front, and 19 inches
(48.3 cm) at the back of the Cisco uBR7225VXR router for installing and replacing
field-replaceable units (FRUs), or accessing network cables or equipment.
• Make sure that blank cable interface line card and blank power supply filler plates are installed in
empty slots.
• The Cisco uBR7225VXR router will receive adequate ventilation (it is being installed in an enclosed
cabinet where ventilation is adequate).
• If you plan to install the cable-management bracket on the front of the chassis, set aside the
cable-management bracket and the four M3 x 6-mm Phillips panhead screws.
Warning
Do not stack the chassis on any other equipment. If the chassis falls, it can cause severe bodily injury
and equipment damage.
Statement 48
Complete the following steps to install the Cisco uBR7225VXR router on a workbench or tabletop:
Step 1Remove any debris and dust from the tabletop or workbench, and the surrounding area. Also make sure
that your path between the router and its new location is unobstructed.
Step 2On the chassis, ensure that all captive installation screws on the network processing engine, cable
interface line cards, and each power supply are tightened.
Warning
Two people are required to lift the chassis. To prevent injury, keep your back straight and lift with your
legs, not your back.
Step 3Add the five rubber feet supplied with the accessory kit to the base of the chassis. Five indented circles
are provided on the base of the chassis to indicate the location to which the rubber feet can be added.
Step 4Place the Cisco uBR7225VXR router on the tabletop or workbench.
Step 5Ensure that there is the appropriate amount of space around the router.
If you want to install a cable-management bracket on the Cisco uBR7225VXR router, proceed to the
following section, “Installing the Cable-Management Bracket on a Cisco uBR7225VXR Router in a
Workbench or Tabletop Environment.” Otherwise, proceed to the “Cabling” section on page 3-13.
Installing the Cable-Management Bracket on a Cisco uBR7225VXR Router in a
Workbench or Tabletop Environment
To install the cable-management bracket on a Cisco uBR7225VXR universal broadband router installed
on a workbench or tabletop, complete the following steps:
Step 1Locate the threaded holes in the right front side of the chassis.
Step 2Align the cable-management bracket with the two threaded holes on the front or rear side of the
Step 3Thread two M3 x 6-mm Phillips panhead screws through the bracket and into the chassis. Use a number
Cabling
Warning
Cisco uBR7225VXR chassis. (See Figure 3-7 on page 3-6.)
2 Phillips screwdriver to tighten the screws.
This completes the steps for installing the cable-management bracket on the Cisco uBR7225VXR router.
Proceed to, “Cabling” section on page 3-13 to continue the installation.
This section provides information on connecting cable interface cards, auxiliary and console ports to
your Cisco uBR7225VXR universal broadband router.
This product is not intended to be directly connected to the Cable Distribution System. Additional
regulatory compliance and legal requirements may apply for direct connection to the Cable
Distribution System. This product may connect to the Cable Distribution System ONLY through a device
that is approved for direct connection.
Statement 1078
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Warning
The intra-building port(s) of the equipment or subassembly is suitable for connection to intra-building
or unexposed wiring or cabling only. The intra-building port(s) of the equipment or subassembly
MUST NOT metallically connect to interfaces that connect to the OSP or its wiring. These interfaces
are designed for use as intra-building interfaces only (Type 2 or Type 4 ports as described in
GR-1089-CORE, Issue 4) and require isolation from the exposed OSP cabling. The addition of Primary
Protectors is not sufficient protection in order to connect these interfaces metallically to OSP wiring.
CautionTo comply with GR-1089-Core intra-building lightning-immunity requirements, you must use shielded
(screened) cable that is grounded at both ends.
Connecting Cable Interface Line Card Cables
The instructions for connecting the cables for each cable interface line card installed in the
Cisco uBR7225VXR universal broadband router are contained in the cable interface line card
installation document. Refer to the Cisco uBR7200 Series Interface Line CardHardware Installation Guide at the following URL:
http://www.cisco.com/en/US/docs/interfaces_modules/cable/line_cards/installation/guide/mcxxfru.htm
l
Console and Auxiliary Port Connection Equipment
The NPE contains the console and auxiliary ports. The console port is a RJ-45 receptacle for connecting
a data terminal, which you use to configure the interfaces and bring up the Cisco uBR7255VXR router.
The auxiliary port is a RJ-45 receptable for connecting a modem or the other DCE device (such as a
channel service unit/data service unit [CSU/DSU]) to the router. (See Figure 3-12 on page 3-14.)
NoteBoth the console and auxiliary ports are asynchronous ports; any devices connected to these ports must
be capable of asynchronous transmission. (Asynchronous is the most common type of serial device; for
example, most modems are asynchronous devices.)
Before connecting a terminal to the console port, configure the terminal to match the
Cisco uBR7225VXR router console port as follows:
• 9600 baud
• 8 data bits
• No parity
• 1 stop bit (9600 8N1)
You need an RJ-45 console cable to connect the terminal to the console port. After you establish normal
universal broadband router operation, you can disconnect the terminal.
You must supply your own interface cable between the auxiliary port and the equipment you are
connecting. For console and auxiliary port pinouts, refer to the “Console Port Signals” section on
page 3-15 and the “Auxiliary Port Signals” section on page 3-15.
Console Port Signals
Both Data Set Ready (DSR) and Data Carrier Detect (DCD) signals are active when the system is
running. The Request To Send (RTS) signal tracks the state of the Clear To Send (CTS) input. The
console port does not support modem control or hardware flow control. Tab le 3-2 lists the signals used
on the console port. The console port requires a straight-through EIA/TIA-232 cable.
Console and Auxiliary Port Connection Equipment
Table 3-2Console Port Signal
PinSignalDirectionDescription
1GND–Ground
2TxD<—Transmit Data
3RxD—>Receive Data
6DSR—>Data Set Ready (always on)
7GND–Ground
8DCD—>Data Carrier Detect (always on)
Auxiliary Port Signals
Table 3-3 lists the signals used on the auxiliary port. The auxiliary port supports hardware flow control
and modem control.
Table 3-3Auxiliary Port Signals
PinSignalDirectionDescription
2TxD —>Transmit Data
3RxD <—Receive Data
4RTS—>Request To Send (used for hardware flow control)
5CTS<—Clear To Send (used for hardware flow control)
20DTR —>Data Terminal Ready (used for modem control only)
Protective Grounding
The building installation should provide a means for connection to the protective earth grounding. The
equipment should be connected to that means.
NoteThe uBR7225VXR is intended for installation in a Common Bonding Network (CBN).
While installing the equipment, the service person should check whether the power source is adequately
grounded. If it is not, the service person should arrange for the installation of a protective grounding
conductor from the equipment to the protective grounding wire in the building. This conductor should
consist of a minimum #6 American Wire Gauge (AWG) stranded copper wire. See Figure 3-13 to
identify the ground lug location.
Chapter 3 Installing the Cisco uBR7225VXR Router
Figure 3-13Cisco uBR7225VXR Ground Lug Location
Ground lug location
1
Connecting Power
Following are the procedures for connecting AC-input power to your Cisco uBR7225VXR universal
broadband router.
Warning
Warning
High leakage current - earth connection essential before connecting to system power supply.
Statement 342
Care must be given to connecting units to the supply circuit so that wiring is not overloaded.
Read the installation instructions before you connect the system to its power source.
Statement 1004
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Chapter 3 Installing the Cisco uBR7225VXR Router
Connecting Power
Warning
Warning
Warning
NoteDetailed instructions for handling and replacing the Cisco uBR7225VXR router power supplies are
Before working on equipment that is connected to power lines, remove jewelry (including rings,
necklaces, and watches). Metal objects will heat up when connected to power and ground and can
cause serious burns or weld the metal object to the terminals.
This equipment is intended to be grounded to comply with emission and immunity requirements.
Ensure that the switch functional ground lug is connected to earth ground during normal use.
Statement 1064
This equipment must be grounded. Never defeat the ground conductor or operate the equipment in the
absence of a suitably installed ground conductor. Contact the appropriate electrical inspection
authority or an electrician if you are uncertain that suitable grounding is available.
contained in the Cisco uBR7200 Series Universal Broadband Router AC-Input Power Supply
Replacement Instructions at the following URL:
NoteIf the cable interface line card or the network processing engine is not properly seated or not fully locked
into place, the Cisco uBR7225VXR router might enter a continuous restart loop. Make sure that the
boards are seated and locked into position.
• Hybrid fiber-coaxial (HFC) network coaxial cable is connected to the cable interface line cards.
• A CompactFlash Disk is installed in a CompactFlash Disk slot in the front panel of the NPE-G1 or
NPE-G2. Use only authorized Cisco provided CompactFlash Disks.
• Each AC-input power cable is connected.
• The console terminal is turned on.
Step 2At the rear of the Cisco uBR7225VXR router, place the power switch on the power supply in the on (|)
position. Repeat this step if a second power supply is installed. The power supply OK LEDs comes on.
Step 3Listen for the fans; you should immediately hear them operating. In a very noisy environment, also look
for air movement around the chassis to verify that the fans are operating. If the Cisco uBR7225VXR
router was recently switched off, it might take up to 90 seconds for the power supply to restart and the
fans to start operating.
Configuring the Interfaces
NoteTo facilitate headend installation, a Cisco uBR7225VXR universal broadband router equipped with at
least one cable interface line card generates a downstream IF carrier when it starts running.
The downstream IF carrier will be present if a cable interface line card is properly installed and passes
diagnostics, the router has been powered on for more than two minutes, the IF downstream shutdown
command (no cable downstream if-output) has not been configured, or the Cisco uBR7225VXR router
is not in ROMMON mode. The amplitude and shape of the downstream IF carrier will not change after
the Cisco uBR7225VXR router is configured, unless a non-DOCSIS data rate is configured.
Step 4Observe the initialization process. When the system boot is complete (a few seconds), the network
processing engine begins to initialize the cable interface line cards. During this initialization, the LEDs
on each cable interface line card behave differently (most flash on and off). The enabled LED on each
cable interface line card goes on when initialization is complete, and the console screen displays a script
and system banner similar to the following:
Cisco IOS Software, 7200 Software (UBR7200-K9PU2-M), Version 12.2(33)SCA, RELEASE SOFTWARE
(fc1)
Technical Support: http://www.cisco.com/techsupport
Copyright (c) 1986-2008 by Cisco Systems, Inc.
Compiled Thu 14-Feb-08 13:58 by prod_rel_team
Configuring the Interfaces
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When you start up the Cisco uBR7225VXR router for the first time, the system automatically enters the
setup facility (also called the system configuration dialog), which determines which cable interface
cards are installed. The setup facility prompts you for configuration information.
On the console terminal, after the system displays the system banner and hardware configuration, the
following System Configuration Dialog prompt appears:
At any point you may enter a questions mark ‘?’ for help.
Use ctrl-c to abort configuration dialof at any prompt.
Default settings are in square brackets ‘[]’.
continue with configuration dialog? [yes]:
You can proceed with the setup facility or exit from the setup facility, using the command interface to
configure global (system-wide) and interface-specific parameters.
have a default state of “shutdown” after the setup facility is run. You must configure upstream
parameters. For additional information, refer to the Cisco uBR7200 Series Software Configuration Guide
at the following URL:
You do not have to configure the interfaces immediately; however, you cannot enable the interfaces or
connect them to any networks until you have configured them.
Many of the cable interface line card LEDs do not come on until you have configured the interfaces. To
verify correct operation of each interface, complete the first-time startup procedures and configuration,
then refer to the document for each cable interface line card for LED descriptions and to check the status
of the interfaces.
Your Cisco uBR7225VXR chassis installation is complete. To set up your cable network headend,
proceed to Chapter 4, “Connecting the Cisco uBR7225VXR Router to the Cable Headend.” To begin
configuring your Cisco uBR7225VXR router, see the Cisco uBR7200 Series Software Configuration Guide at the following URL:
Connecting the Cisco uBR7225VXR Router to the
Cable Headend
This chapter describes how to connect the Cisco uBR7225VXR universal broadband router to a cable
headend and contains the following sections:
• Two-Way Data Headend Architecture, page 4-2
• One-Way Data Headend Architecture, page 4-3
• RF and Digital Data Overview, page 4-3
• Connecting and Configuring the Downstream, page 4-4
• Measuring the Downstream RF Signal, page 4-4
• Connecting and Configuring the Upstream, page 4-18
• Measuring the Upstream RF Signal, page 4-22
• Measuring the RF Signal at the Forward Test Point on a Laser Transmitter, page 4-37
• Configuring the Digital Signal, page 4-40
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NoteBefore installing your Cisco uBR7225VXR router, analyze the radio frequency (RF) setup at your
headend and configure the analog RF signals for interaction with digital data. This chapter guides you
through the process of configuring the RF and digital data at the headend for optimal performance.
Chapter 4 Connecting the Cisco uBR7225VXR Router to the Cable Headend
One-Way Data Headend Architecture
Figure 4-2 shows a typical headend configuration configured for one-way (downstream) data in a telco
return cable system.
Figure 4-2Typical Cable Headend Configuration for One-Way (Telco Return) Data
headend feed
0 to 20 dB
attenuator
(as required)
DHCP
TFTP
TOD
servers
Cisco
uBR7225VXR
Downstream
Main
8-way
tap
One-Way Data Headend Architecture
Laser
transmitter
Broadcast
Narrowcast
3-way
splitter
+17 dBmV
video carrier
(typical)
+7 dBmV
data carrier
(typical)
Optical
splitter
Node 1
Node 2
Downstream
forward
test point
Upstream
RF and Digital Data Overview
This section describes the interaction of digital and analog RF data as both signals are carried on the
hybrid fiber-coaxial (HFC) network.
Two-way digital data signals are more susceptible than one-way signals to stresses in the condition of
the HFC network. Degradation in video signal quality might not be noticed, but when two-way digital
signals share the network with video signals, digital signals might be hampered by the following types
of network impairments:
• Impulse and electrical noise—Impulse and electrical noise, usually forms of ingress, can enter the
network from sources within a home, such as hair dryers, light switches, and thermostats; or from
high-voltage lines that run near CATV cabling in the network. Areas of signal ingress may be located
and repaired by implementing a comprehensive signal leakage maintenance program.
• Amplifier thermal noise—Amplifiers add noise to the HFC network that usually goes unnoticed in
video signals, assuming a properly designed and operated network. Improperly configured
amplifiers will degrade digital data signals. The larger the network, the higher the probability of
amplifier thermal noise affecting the signals.
• Ingress noise—Ingress noise includes electrical sources (see “Impulse and electrical noise” above);
amateur radio transmissions; citizens band radios; or high-power shortwave broadcast signals,
which can interfere with frequencies anywhere between 3 and 65 MHz. These often are picked up
by cabling and equipment in the network.
IP network access
RADIUS dial
security server
Cisco network
access server
Telco return
cable modems
PSTN
271672
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NoteSome HFC upstream equipment passes interfering signals below 5 MHz, which may overload the reverse
Chapter 4 Connecting the Cisco uBR7225VXR Router to the Cable Headend
Connecting and Configuring the Downstream
• Noise funneling—The upstream data path to the headend is susceptible to picking up noise and
interference from anywhere in the network, and all upstream noise ultimately ends up at the
headend. This effect is known as noise funneling because of the cumulative nature of the noise from
one or more locations in the network that becomes concentrated at the headend. As a network
serviced by a single upstream receiver increases in size, the probability of noise funneling also
increases.
• Variable transmit levels—Signal loss over coaxial cable is affected by temperature. This can cause
variations of 6 to 10 dB per year.
• Clipping—The lasers in fiber-optic transmitters can stop transmitting light (clipping) when input
levels are excessive. Excessive input levels may cause bit errors and reduced data throughput in both
the upstream and downstream transmissions. If a laser is overdriven as briefly as a fraction of a
second, clipping can occur.
Connecting and Configuring the Downstream
After you install the Cisco uBR7225VXR universal broadband router in your headend site, you must
connect the Cisco uBR7225VXR router to the HFC network and configure the network. The following
sections describe how to connect to and configure the downstream.
Installing and Configuring the Upconverter
The Cisco uBR-MC16U/E-16U and Cisco uBR-MC28U/E-28U cable interface line cards have an
onboard integrated upconverter that generates an RF signal suitable for connection to a combiner and
transmission on the coaxial cable network, without the need for any external upconverters.
NoteFor more information, refer to the Cisco uBR7200 Series Cable Interface Line Card Hardware
Installation Guide at the following URL:
http://www.cisco.com/en/US/docs/interfaces_modules/cable/line_cards/installation/guide/mcxxfru.htm
l
Measuring the Downstream RF Signal
The configuration of the downstream digitally modulated carrier at the headend is critical to the
performance of the Cisco uBR7225VXR universal broadband router and cable modems. The following
guidelines are provided to assist you in configuring the RF signal to the necessary specifications. There
are two options you can use to measure the RF signal with a spectrum analyzer. These options are
described in the following sections:
• Measuring the Downstream RF Signal Using the Channel Power Option on a Spectrum Analyzer,
page 4-5
• Measuring the Downstream RF Signal Using CATV Mode on a Spectrum Analyzer, page 4-11
Chapter 4 Connecting the Cisco uBR7225VXR Router to the Cable Headend
These two sections describe the procedures necessary to use a spectrum analyzer. You may also use a
signal level meter that has the ability to measure the average power level of digitally modulated carriers,
as well as a QAM analyzer. Some instruments to perform these measurements include:
If you complete these measurements using one of the previously mentioned options, your downstream
signal can be verified as correctly configured and it can assist you with troubleshooting your network
later on.
If you want to measure the downstream RF signal using the spectrum analyzer channel power option,
proceed to the following section, “Measuring the Downstream RF Signal Using the Channel Power
Option on a Spectrum Analyzer.” If you want to measure the downstream RF signal using CATV mode,
proceed to the “Measuring the Downstream RF Signal Using CATV Mode on a Spectrum Analyzer”
section on page 4-11.
Measuring the Downstream RF Signal
Measuring the Downstream RF Signal Using the Channel Power Option on a
Spectrum Analyzer
The following sections describe how to measure the downstream RF signal using the channel power
option on a spectrum analyzer:
• Measuring the Downstream IF Signal at the Cisco uBR7225VXR Router, page 4-5
• Measuring the Downstream RF Signal at the Upconverter Output, page 4-7
Measuring the Downstream IF Signal at the Cisco uBR7225VXR Router
NoteRefer to the user guide that accompanied your spectrum analyzer to determine the exact steps required
to use your analyzer to perform these measurements.
Step 1Connect a spectrum analyzer to the downstream connector on a Cisco cable interface line card installed
in a Cisco uBR7225VXR router.
Step 2Turn the power switch on the spectrum analyzer to the ON position.
Step 3Set the spectrum analyzer to view the downstream intermediate frequency (IF) signal with a center
frequency of 44 MHz for a North American headend or 36.125 MHz for a European headend.
Step 4Set the span to 10 MHz. Your analyzer should display a signal similar to the one shown in Figure 4-3.
Figure 4-3Viewing the Downstream IF Signal on a Spectrum Analyzer
Chapter 4 Connecting the Cisco uBR7225VXR Router to the Cable Headend
Step 5
Measure the IF signal using the channel power option on your spectrum analyzer. Set your channel
spacing and your channel bandwidth to 6 MHz. Your analyzer should display a signal similar to the one
shown in Figure 4-4.
Figure 4-4Measuring the IF Channel Power
NoteThe IF channel power in Figure 4-4 is +34.23 dBmV, as displayed on the spectrum analyzer.
4-6
Step 6Select the video averaging feature. Your spectrum analyzer should display a signal similar to the one
Chapter 4 Connecting the Cisco uBR7225VXR Router to the Cable Headend
Figure 4-5Measuring the IF Channel Power Using Video Averaging
Measuring the Downstream RF Signal
NoteThe approximate in-channel peak-to-valley flatness may be verified using the spectrum analyzer’s video
averaging feature. Be aware, however, that amplitude values registered while in the video averaging
mode are typically around 2.5 dB below the actual channel power.
Measuring the Downstream RF Signal at the Upconverter Output
Step 1Disconnect the spectrum analyzer from the cable interface line card downstream connector.
Step 2Connect the downstream output of the cable interface line card to the upconvertor input connector.
Step 3Connect the spectrum analyzer to the RF output of the upconverter. If your spectrum analyzer input is
overloaded, you might see artifacts that are internally generated by the spectrum analyzer. The artifacts
are circled on the analyzer trace shown in Figure 4-6. Add attenuation as necessary to correct the
overload condition.
Chapter 4 Connecting the Cisco uBR7225VXR Router to the Cable Headend
Step 4
Set the input of the upconverter to a digital QAM signal and the output level to the manufacturer’s
recommended settings. Typical output amplitudes range from +50 to +58 dBmV, although DOCSIS
specifies +61 dBmV.
Step 5Set the spectrum analyzer to view the RF signal at the center frequency you selected for your headend.
In this example, the RF center frequency is 699 MHz. Set your span to 20 MHz. Finally, set your channel
spacing and your channel bandwidth to 6 MHz.
If the RF signal is causing an overload condition on the spectrum analyzer input, your analyzer might
display a signal similar to the one shown in Figure 4-7. The sloping of the lines at the sides of the signal
indicates a false reading.
Figure 4-7Measuring the RF Signal at the Upconverter Output—Overload Condition
4-8
Step 6
If you add attenuation to the input to the spectrum analyzer you can correct the overload condition as
shown in Figure 4-8.
Chapter 4 Connecting the Cisco uBR7225VXR Router to the Cable Headend
Figure 4-8Measuring the RF Signal at the Upconverter Output—Overload Condition Corrected
with Attenuation
Measuring the Downstream RF Signal
Step 7
Change the spectrum analyzer settings to view the digital channel power. This setting enables you to see
if there is too much power on the upconverter output. In Figure 4-9, the upconverter output is reading
+64.31 dBmV, which is beyond the DOCSIS-specified range of +50 to +61 dBmV.
TipA spectrum analyzer might become overloaded and produce false readings (such as internally generated
spurs) when measuring a signal at this amplitude.
Figure 4-9Measuring the RF Signal at the Upconverter Output—Upconverter Output Level Too
High
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Step 8
Adjust the power on the upconverter output to ensure that it is between +50 and +61 dBmV. In
Figure 4-10, the upconverter output is reading +57.06 dBmV, which is within the correct range.
Figure 4-10Measuring the RF Signal at the Upconverter Output—Output Adjusted to Correct
Chapter 4 Connecting the Cisco uBR7225VXR Router to the Cable Headend
Range
Step 9
Select the video averaging feature on the spectrum analyzer. The signal becomes smoother and
frequency response problems might become visible. Your analyzer now displays an RF signal similar to
the one shown in Figure 4-11.
Figure 4-11Measuring the RF Signal at the Upconverter Output Using Video Averaging
4-10
NoteThe approximate in-channel peak-to-valley flatness may be verified using the spectrum analyzer’s video
averaging feature. Be aware, however, that amplitude values registered while in the video averaging
mode are typically around 2.5 dB below the actual channel power.
Chapter 4 Connecting the Cisco uBR7225VXR Router to the Cable Headend
Measuring the Downstream RF Signal
Step 10Verify that your headend RF measurements meet the recommended DOCSIS parameters listed in the
tables in Appendix B, “RF Specifications.” Record your headend settings and measurements in your
headend site log (Appendix G, “Site Log”). This will assist in troubleshooting the
Cisco uBR7225VXR router installation later in the process.
This completes the procedure to measure the downstream RF signal using the channel power option.
Proceed to the “Measuring the RF Signal at the Forward Test Point on a Laser Transmitter” section on
page 4-37.
Measuring the Downstream RF Signal Using CATV Mode on a
Spectrum Analyzer
The following two sections describe the methods you may use to measure the downstream RF signal
using CATV mode (digital channel power option) on a spectrum analyzer:
• Measuring the Downstream IF Signal at the Cisco uBR7225VXR Router Using CATV Mode,
page 4-11
• Measuring the Downstream RF Signal at the Upconverter Output Using CATV Mode, page 4-14
NoteWe recommend using as recent a model of spectrum analyzer as possible to perform the two analyses
described here. You can use spectrum analyzers, such as the Agilent 8591C (http://www.tm.agilent.com)
or the Tektronix 2715 (http://www.tek.com) to help you perform the tasks outlined in this section.
Measuring the Downstream IF Signal at the Cisco uBR7225VXR Router Using CATV Mode
NoteRefer to the user guide that accompanied your spectrum analyzer to determine the exact steps required
to use your analyzer to perform these measurements.
Step 1Connect a spectrum analyzer to the downstream connector on a Cisco cable interface card installed in a
Cisco uBR7225VXR router.
Step 2Turn the power switch on the spectrum analyzer to the on position.
Step 3Set the spectrum analyzer to CATV mode (CATV analyzer option) and select the channel measurement
option to view the downstream intermediate frequency (IF) signal. Your analyzer should display a signal
similar to the one shown in Figure 4-12.
NoteFigure 4-12 shows the first of three screens that will be displayed by an Agilent 8591C when you use the
analyzer in this mode. Figure 4-13 is the last of the three screens displayed.
Figure 4-12Viewing the Downstream IF Signal on a Spectrum Analyzer in CATV Mode—Initial
Chapter 4 Connecting the Cisco uBR7225VXR Router to the Cable Headend
Screen
Step 4Advance to the last of the three screens in this display. Your analyzer should display a signal similar to
the one shown in Figure 4-13.
Figure 4-13Viewing the IF Signal on a Spectrum Analyzer in CATV Mode—Preliminary Digital
Channel Power Screen
Step 5
Enter a digital channel to measure and select digital channel power. Your spectrum analyzer will display
a signal similar to the one shown in Figure 4-14.
Chapter 4 Connecting the Cisco uBR7225VXR Router to the Cable Headend
Figure 4-14Measuring the IF Signal on a Spectrum Analyzer in CATV Mode—Digital Channel
Power Screen
Measuring the Downstream RF Signal
Step 6
Using the spectrum analyzer’s reference level control, adjust the amplitude of the displayed signal until
the shape of the signal is clearly distinguishable as a digitally modulated carrier, as shown in
Figure 4-15.
Figure 4-15Measuring the IF Signal on a Spectrum Analyzer in CATV Mode—Adjusted Digital
Channel Power Screen
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NoteThe IF channel power in Figure 4-15 is +33 dBmV, as displayed on the spectrum analyzer.
Step 7Select the video averaging feature. Your spectrum analyzer should display a signal similar to the one
Figure 4-16Measuring the IF Signal on a Spectrum Analyzer in CATV Mode—Digital Channel
Chapter 4 Connecting the Cisco uBR7225VXR Router to the Cable Headend
Power Screen (Using Video Averaging)
NoteThe approximate in-channel peak-to-valley flatness can be verified using the spectrum analyzer’s video
averaging feature. Be aware, however, that amplitude values registered while in the video averaging
mode are typically around 2.5 dB below the actual channel power.
Proceed to the next section, “Measuring the Downstream RF Signal at the Upconverter Output Using
CATV Mode.”
Measuring the Downstream RF Signal at the Upconverter Output Using CATV Mode
Step 1Disconnect the spectrum analyzer from the cable interface card downstream connector.
Step 2Connect the downstream output of the cable interface card to the upconverter input connector.
Step 3Connect the spectrum analyzer to the RF output of the upconverter.
Step 4Set the upconverter output level to the manufacturer’s recommended settings. Typical output amplitudes
range from +50 to +58 dBmV, although DOCSIS specifies levels as high as +61 dBmV.
Step 5Set the spectrum analyzer to view the RF signal at the center frequency you selected for your headend.
In this example, the RF center frequency is 705 MHz.
Step 6Set the spectrum analyzer to CATV mode (CATV analyzer option) and select the channel measurement
option to view the downstream RF signal. Your spectrum analyzer should display a signal similar to the
one shown in Figure 4-12.
4-14
NoteFigure 4-17 shows the first of three screens that will be displayed by an Agilent 8591C when you use the
analyzer in this mode. Figure 4-18 is the last of the three screens displayed.
Chapter 4 Connecting the Cisco uBR7225VXR Router to the Cable Headend
Figure 4-17Viewing the Downstream RF Signal on a Spectrum Analyzer in CATV Mode—Initial
Screen
Measuring the Downstream RF Signal
Step 7
Step 8
Advance to the last of the three screens in this display. Your analyzer should display a signal similar to
the one shown in Figure 4-18.
Figure 4-18Viewing the RF Signal on a Spectrum Analyzer in CATV Mode—Preliminary Digital
Channel Power Screen
Enter a digital channel to measure and select digital channel power. Your spectrum analyzer will display
a signal similar to the one shown in Figure 4-19.
Figure 4-19Measuring the RF Signal at the Upconverter Output in CATV Mode—Digital Channel
Chapter 4 Connecting the Cisco uBR7225VXR Router to the Cable Headend
Power Screen
Step 9
Step 10
Using the spectrum analyzer’s reference level control, adjust the amplitude of the displayed signal until
the signal peak is within the top graticule of the analyzer’s display grid, as shown in Figure 4-20.
Figure 4-20Measuring the RF Signal at the Upconverter Output in CATV Mode—Adjusted Digital
Channel Power Screen
Select the video averaging feature. Your spectrum analyzer should display a signal similar to the one
shown in Figure 4-21.
Chapter 4 Connecting the Cisco uBR7225VXR Router to the Cable Headend
Figure 4-21Measuring the RF Signal at the Upconverter Output in CATV Mode—Digital Channel
Power Screen Using Video Averaging
Measuring the Downstream RF Signal
NoteThe approximate in-channel peak-to-valley flatness can be verified using the spectrum analyzer’s video
averaging feature. Be aware, however, that amplitude values registered while in the video averaging
mode are typically around 2.5 dB below the actual channel power.
Step 11Verify that your headend RF measurements meet the recommended DOCSIS parameters listed in the
tables in Appendix B, “RF Specifications.”
Step 12Record your headend settings and measurements in Appendix G, “Site Log.” as you verify them. This
will assist in troubleshooting the Cisco uBR7225VXR router installation later in the process.
Step 13After you have analyzed and adjusted the RF signal according to the steps outlined on the preceding
pages, proceed to the “Connecting and Configuring the Upstream” section on page 4-18.
Chapter 4 Connecting the Cisco uBR7225VXR Router to the Cable Headend
Connecting and Configuring the Upstream
Connecting and Configuring the Upstream
The following sections describe how to connect and configure the upstream for digital data.
Connecting the Upstream to the Optical Receiver
To connect the upstream to the optical receiver, use a 2-way splitter as a combiner to leave the DOCSIS
cable modem connected at the headend, and connect the upstream headend cable to the optical receiver.
(See Figure 4-22.)
The default upstream input level to the Cisco uBR7225VXR cable interface line card is 0 dBmV. You
may adjust the upstream input level to other values using the Cisco IOS software running on your router.
The Cisco uBR7225VXR router uses automatic power control when transmitting to remote
cable modems. Accurately setting the power level helps to ensure reliable cable modem operation.
Table 4-1 provides upstream input power ranges for the various cable interface line cards available for
the Cisco uBR7225VXR router, depending on the channel bandwidth you are using.
Table 4-1Upstream Input Power Ranges According to Cable Interface Line Card Type
Channel BandwidthCisco MC11 FPGACisco MC16E and MC16SDOCSIS Specification
200 KHzN/A–10 to +25 dBmV–16 to +14 dBmV
400 KHzN/A–10 to +25 dBmV–13 to +17 dBmV
800 KHzN/A–10 to +25 dBmV–10 to +20 dBmV
1.6 MHz–10 to +10 dBmV–10 to +25 dBmV–7 to +23 dBmV
3.2 MHzN/A–10 to +25 dBmV–4 to +26 dBmV
NoteIf you have a Cisco uBRMC16x cable interface line card (six upstream ports and one downstream port)
installed in your Cisco uBR7225VXR router, the 2-way splitter described above would be replaced by
six 2-way splitters (one splitter per upstream port). This would enable you to connect to all of the
available upstream ports on the Cisco uBRMC16x.
Chapter 4 Connecting the Cisco uBR7225VXR Router to the Cable Headend
14045
Spectrum analyzer
Optical
receiver
Fiber node
0.5 milliwatt
Fiber node
1.0 milliwatt
Spectrum analyzer
Optical
receiver
1dB attenuator
+11 dBmV
X-level test point = +10 dBmV
(in this example)
30 km
10 km
+17 dBmV
Insert +17 dBmV signal
X
Measure +10 dBmV at this point
Insert +17 dBmV signal
Figure 4-22Connecting and Configuring the Upstream
Cisco
uBR7225VXR
Upstream
2-way
splitter
(combiner)
10 dB
attenuator
Diplex filter
40 dB
attenuator
Cable
modem
X-level test point signal level
must be the same for all
optical receivers (+/- 0.5 dB),
See Fig. 4-36 and Fig 4-37
LH
C
To downstream forward
test point on laser transmitter
Connecting and Configuring the Upstream
Optional attenuator
X
to adjust X-level point
measurement
Optical
receiver
271676
Testing the Upstream Configuration
To test the upstream configuration, insert a test signal of known amplitude (+17 dBmV is shown in this
example) into the fiber node and measure the amplitude output level at the output of the headend’s
optical receiver. This measurement depends on return laser performance and optical distance. This
procedure is known as establishing the “X-level” test point. (See Figure 4-23.)
Chapter 4 Connecting the Cisco uBR7225VXR Router to the Cable Headend
Cisco
uBR7225VXR
Downstream
Upstream
0 dBmV
3 dB
attenuator
3 dB
attenuator
3 dB
attenuator
40 dB
attenuator
3 dB
attenuator
8 dB
attenuator
21 dB
attenuator
Cable
modems
+48 dBmV
+31 dBmV
+42 dBmV
+50 dBmV
+46 dBmV
+49 dBmV
+58 dBmV
4-way
splitter
X
X
X
+10 dBmV
+10 dBmV
+10 dBmV
To downstream
forward test point
on laser transmitter
+13 dBmV
+18 dBmV
+31 dBmV
Reverse optical
transmitter
Optical
receiver
Fiber-optic
cable
Distribution
network
+17 dBmV
Reverse optical
transmitter
Optical
receiver
Fiber-optic
cable
Distribution
network
+17 dBmV
Reverse optical
transmitter
Optical
receiver
Fiber-optic
cable
Distribution
network
+17 dBmV
Modem transmit levels
Modem transmit levels
Modem transmit levels
Cable
modem
LH
C
Diplex filter
Connecting and Configuring the Upstream
This “X-level” test point measurement will be different for every fiber node in the HFC network until
you adjust the attenuation on the upstream. You must adjust the attenuation so that this measurement is
the same on every fiber node. If you change a receiver or a transmitter at the fiber node, or if you unplug
a connector and plug it back in, you must recheck this amplitude measurement. Figure 4-24 shows how
three distribution network “X-level” test points connected to the same upstream port are all calibrated to
+10 dBmV using different attenuators.
Figure 4-24Calibrating Multiple “X-level” Test Points Connected to One Upstream Port
4-20
Figure 4-25 shows how three distribution network “X-level” test points connected to the three different
Chapter 4 Connecting the Cisco uBR7225VXR Router to the Cable Headend
Measuring the Upstream RF Signal
Measuring the Upstream RF Signal
You can use a spectrum analyzer to measure the upstream signal from one or more remote cable modems
in a two-way data cable network. Performing this procedure can help alert you to potential problems in
your cable network’s upstream configuration before a problem occurs. This helps to avoid trying to solve
a problem after a remote cable modem has experienced a failure in service. This procedure is referred to
as the “zero-span” method.
Measuring the Upstream RF Signal Using a Spectrum Analyzer
This procedure is designed to help you accurately measure an upstream RF signal where no adjacent
channels are in use. To measure an upstream RF signal with active adjacent channels, refer to the “Using
the Zero-Span Method with Adjacent Upstream Channels” section on page 4-28.
NoteRefer to the user guide that accompanied your spectrum analyzer to determine the exact steps required
to use your analyzer to perform these measurements.
Step 1Connect the spectrum analyzer to the upstream signal from your cable network.
Step 2Turn the power switch on the spectrum analyzer to the on position.
Step 3Set the spectrum analyzer to view the upstream RF signal with a center frequency matching the actual
upstream center frequency defined in your Cisco uBR7225VXR router configuration file.
Step 4Set the spectrum analyzer’s span to 0 MHz.
NoteYou can view the configuration file for your Cisco uBR7225VXR router by using the
show controller cableslot/upstream/portcommand, available in Cisco IOS Release 11.3(6)NA or later
releases and Cisco IOS Release 12.0(5)T1 or later releases. For example, if you wanted to view the
center frequency of port 0 on a cable interface card in slot 3, you would enter the
show controller cable 3/0 command.
If you have assigned spectrum groups in your configuration file, use the show cable hop command to
display the current upstream center frequency for each cable interface.
Step 5Set both the resolution bandwidth and the video bandwidth on the spectrum analyzer to 3 MHz and the
sweep rate to 20 microseconds. Provided there is a large amount of activity on your upstream channel,
the spectrum analyzer should display a signal similar to the one shown in Figure 4-26.
Chapter 4 Connecting the Cisco uBR7225VXR Router to the Cable Headend
Figure 4-26Measuring the Upstream RF Signal—Setting the Resolution and Video Channel
Bandwidth
Measuring the Upstream RF Signal
TipThe horizontal line passing through the center of the spectrum analyzer display in Figure 4-26 is the
trigger line.
Step 6Set the sweep value to 80 microseconds. Your spectrum analyzer should display a signal similar to the
one shown in Figure 4-27.
NoteBe sure that your particular spectrum analyzer is capable of supporting sweep times as short as 80
microseconds.
Figure 4-27Measuring the Upstream RF Signal—Setting the Sweep Time Period
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Step 7
Position the trigger line on the spectrum analyzer so that it is roughly in the middle (approximately
halfway between the highest and lowest portions) of the upstream RF signal.
NoteRefer to the documentation that accompanied your particular spectrum analyzer for detailed instructions
on activating and positioning the trigger line.
A known workaround exists for the Agilent 8591C spectrum analyzer. After activating and positioning
the trigger line in video mode, you must press the “video” button on the spectrum analyzer once more to
enable proper functionality.
Step 8Adjust the amplitude on your spectrum analyzer so that the uppermost portion of the upstream RF signal
is in the top graticule of the analyzer’s display grid and adjust the trigger line accordingly. Your spectrum
analyzer will then display an upstream RF signal similar to the one shown in Figure 4-28.
NoteWe do not recommend using the spectrum analyzer’s “max-hold” feature while analyzing upstream
signals in the frequency domain. “Max-hold” readings in the frequency domain can be inaccurate
because the analyzer focuses on the peak power of the strongest ranging modem rather than the power
levels of cable modems that are operating in a more ideal range.
Figure 4-28Measuring the Upstream RF Signal—Accurately Measured Amplitude on Spectrum
Chapter 4 Connecting the Cisco uBR7225VXR Router to the Cable Headend
Analyzer
4-24
Step 9
Position a marker about 7/8 of the way into the preamble of the signal, as illustrated in Figure 4-28. (The
preamble is the regular pattern displayed at the front of the signal and the length of the preamble is a
function of the channel width/data rate, modulation format, and DOCSIS burst-profile configurations.)
The peak amplitude of the marker, which registers +31.07 dBmV in this case, will be within 1 dB of the
true burst power.
NoteTo verify this reading, you can also measure the power rating with an Agilent 89441A vector signal
analyzer (http://www.tm.agilent.com).
If the preamble of your upstream signal is displayed with a significantly lower amplitude than the rest
of the RF signal, refer to the “Using the Zero-Span Method with Adjacent Upstream Channels” section
on page 4-28 for instructions on how to overcome this phenomenon.
Chapter 4 Connecting the Cisco uBR7225VXR Router to the Cable Headend
Step 10Verify that your headend RF measurements meet the recommended DOCSIS parameters listed in the
tables in Appendix B, “RF Specifications.”
Step 11Record your headend settings in Appendix G, “Site Log.” This will assist in troubleshooting the
Cisco uBR7225VXR universal broadband router installation later in the process.
NoteBe sure not to narrow the focus of your analysis any further than approximately 3-MHz channel width.
Doing so can yield incorrect readings. For example, if you were to view an upstream RF signal with a
resolution bandwidth of only 300 kHz and a video channel bandwidth of only 100 kHz, your
measurements would register lower than the actual transmission levels.
Analyzing the Upstream RF Signal
When you have set up your spectrum analyzer to accurately read the upstream RF signal, you can verify
that a remote cable modem is operating as it should by pinging the modem via a console terminal.
Measuring the Upstream RF Signal
Step 1Log in to your Cisco uBR7225VXR universal broadband router with a console terminal.
Step 2Adjust the sweep time on your spectrum analyzer to 20 microseconds.
Step 3Ping the remote cable interface card using first a 64-byte, then a 1500-byte ping packet request, and take
note of the upstream RF signal in each case. Several hundred or thousand ping packets might be required
for a usable pattern to emerge.
Figure 4-29 and Figure 4-30 provide two examples of an ideal upstream RF signal based on a simple 64-
or 1500-byte ping of a single remote cable interface. The more slender of the data spikes in the RF signal
(the first and third spikes in Figure 4-29) are bandwidth request packet transmissions, while the larger
spikes are the actual 64- or 1500-byte ping packet returns.
Figure 4-29Analyzing the Upstream RF Signal—64-Byte Data Packets
Figure 4-30Analyzing the Upstream RF Signal—1500-Byte Data Packets
Chapter 4 Connecting the Cisco uBR7225VXR Router to the Cable Headend
NoteBoth of the previous examples feature 16-QAM transmission with a channel width of 3.2 MHz, yielding
a 10-Mbit/sec data rate. In addition, these examples have an optimal upstream carrier-to-noise ratio of
approximately 50 dB.
Now it is time to view your upstream RF signal with multiple remote cable modems. Figure 4-31 and
Figure 4-32 both display upstream RF signals encompassing more than one remote cable modem. In
each case, there are two bandwidth requests followed by their respective ping packet returns, both at
slightly different amplitudes. This situation is most commonly caused by a difference in the receive
power from the two cable modems in question. In the example, the remote cable modem with the lesser
amplitude is “cable modem A” and the other is “cable modem B.”
In the following example, cable modem A and cable modem B have been artificially configured to yield
a larger than normal difference in amplitude between their respective upstream RF transmissions. Under
normal conditions, the maximum difference in amplitude between any cable modems will be about
1.5 dB. Differences greater than 1.5 dB indicate a possible cable plant or remote cable modem problem.
NoteTo further illustrate this point, you can log in to your Cisco uBR7225VXR router using a console
terminal and enter the show cable modem command to obtain a report of the receive power ratings for
each modem. In the example, the receive power ratings for remote cable modems A and B are –2 dBmV
and 0 dBmV, respectively.
The two bandwidth requests and ping packet returns on the upstream RF signal for cable modems A and
B are slightly different in Figure 4-31 and Figure 4-32. Differences in the distance between bandwidth
requests are primarily caused by the contention-based nature of multiple remote cable modems on the
same line. Differences in the distance between ping packet returns are primarily caused by factors such
as packet size and system loading.
Chapter 4 Connecting the Cisco uBR7225VXR Router to the Cable Headend
Figure 4-31Analyzing the Upstream RF Signal—Multiple Active Remote Cable Modems (A)
Measuring the Upstream RF Signal
Figure 4-32Analyzing the Upstream RF Signal—Multiple Active Remote Cable Modems (B)
NoteWhen viewing the upstream RF signal on your spectrum analyzer, two ping packet returns (for example,
from remote cable modems A and B) can be so close together that they appear to be one rather large
packet with a slight jump or decline in amplitude halfway through the measurement. This is an indication
that the upstream is 100 percent occupied during this time.
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Figure 4-33 shows an upstrea m RF si gnal from a re mote cable modem in a “real-life” scenario including
outside plant noise. Notice the relatively tall spike at the very left edge of the ping packet return. This
spike is mainly additive noise associated with an upstream RF signal mired by excessive amounts of
severe outside plant noise (as in this example). In addition, notice that the carrier-to-impulse noise ratio
measurement between the two diamond-shaped markers is only about 12 dB. (A few other noise peaks
are even worse.)
The importance of this example is to bring to your attention the need for minimal outside plant noise.
Time-varying, fast noise can cause bit errors in packet transmissions, rendering your communication link
unreliable, if not unusable.
Figure 4-33Analyzing the Upstream RF Signal—Outside Plant Noise Included
Chapter 4 Connecting the Cisco uBR7225VXR Router to the Cable Headend
NoteThis illustration depicts an upstream RF signal whose carrier-to-impulse noise ratio does not meet
DOCSIS 1.0 specifications. The data packet in Figure 4-33 was “dropped” due to severe noise
interference with a more narrow resolution bandwidth.
Using the Zero-Span Method with Adjacent Upstream Channels
When measuring upstream signals using the zero-span method, a very wide resolution and video
bandwidth give very accurate readings, but render your readings susceptible to energy in adjacent
channels. As the number of upstream services increases, so does the likelihood of interference from
adjacent channels. This section describes using the zero-span power measurement method, with a more
narrow resolution bandwidth.
Simply narrowing the resolution bandwidth will not yield accurate readings. See Tab le 4- 2.
Table 4-2Sample Channel Width and Symbol Rate Combinations with Their Respective Minimum Resolution
Chapter 4 Connecting the Cisco uBR7225VXR Router to the Cable Headend
Step 1Display a signal complete with preamble and upstream data transmission information similar to the
resulting signal from Step 3 through Step 10 under the “Measuring the Upstream RF Signal Using a
Spectrum Analyzer” section on page 4-22. Your spectrum analyzer should display a signal similar to the
one in Figure 4-34.
Figure 4-34Preamble Amplitude Before Resolution and Video Bandwidth Reduction
Measuring the Upstream RF Signal
NoteFigure 4-34 is a display from a standard spectrum analyzer. The following figures, Figure 4-35 through
Figure 4-38, are taken from a vector signal analyzer. If you do not have access to a vector signal analyzer,
or want to skip the following section describing its use when viewing your upstream signal, proceed to
Step 3.
Step 2(Optional) View your upstream signal using a vector signal analyzer such as the Agilent 89441A.
The advantage of displaying these signals with the vector signal analyzer is that you can view them over
the time domain for a specified time interval. In addition, the vector signal analyzer enables you to
measure the digital channel power of a very short duration data transmission, like the preamble of a
digital signal.
a. Set up your vector signal analyzer to view both the “frequency” domain and “time” domain of your
upstream signal. Your vector signal analyzer should display a pair of signals similar to those in
Figure 4-35Vector Signal Analyzer Plot of Upstream Data Burst
Chapter 4 Connecting the Cisco uBR7225VXR Router to the Cable Headend
The upper graph in Figure 4-35 represents the frequency domain and the lower graph represents the
time domain.
In the time domain, the channel power of the preamble of a digital upstream signal is not spread
across the entire channel. However, the channel power of the remainder of the digital transmission
is spread across the entire channel. Even though it may not seem so, the total channel power across
both the preamble and the subsequent data segment remains constant.
b. Narrow the view on your vector signal analyzer to display only the preamble of the digital data
signal in both the frequency domain and time domain.
The upper display in Figure 4-36 is a plot of only the preamble portion of the digital signal in
Figure 4-35. Notice how the amplitude of the signal experiences many “peaks” and “valleys.” When
you are measuring the preamble power using the zero-span method, be sure that you measure the
actual signal energy (a peak), rather than accidentally measuring the power level of a valley in the
preamble.