Frontmat.fm Page i Tuesday, October 10, 2000 3:11 PM
Reference Guide for the
Model RT328 and Model
RH348 ISDN Routers
NETGEAR , Inc.
4500 Great America Parkway
Santa Clara, CA 95054
USA
M-RH348NA-2
September 2000
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© 2000 by NETGEAR, Inc. All rights reserved.
Trademarks
NETGEAR™ is a trademark of Netgear, Inc. Windows® is a registered trademark of Microsoft Corporation. Other
brand and product names are trademarks or registered trademarks of their respective holders. Information is subject to
change without notice. All rights reserved.
Statement of Conditions
In the interest of improving internal design, operational function, and/or reliability, NETGEAR reserves the right to
make changes to the products described in this document without notice.
NETGEAR does not assume any liability that may occur due to the use or application of the product(s) or circuit
layout(s) described herein.
Federal Communications Commission (FCC) Compliance Notice: Radio Frequency Notice
This device complies with part 15 of the FCC Rules. Operation is subject to the following two conditions:
• This device may not cause harmful interference.
• This device must accept any interference received, including interference that may cause undesired operation.
Note : This equipment has been tested and found to comply with the limits for a Class B digital device, pursuant to
part 15 of the FCC Rules. These limits are designed to provide reasonable protection against harmful interference in a
residential installation. This equipment generates, uses, and can radiate radio frequency energy and, if not installed and
used in accordance with the instructions, may cause harmful interference to radio communications. However, there is no
guarantee that interference will not occur in a particular installation. If this equipment does cause harmful interference to
radio or television reception, which can be determined by turning the equipment off and on, the user is encouraged to try
to correct the interference by one or more of the following measures:
• Reorient or relocate the receiving antenna.
• Increase the separation between the equipment and receiver.
• Connect the equipment into an outlet on a circuit different from that to which the receiver is connected.
• Consult the dealer or an experienced radio/TV technician for help.
EN 55 022 Decla0ration of Conformance
This is to certify that the Model RT328 ISDN Router and the Model RH348 ISDN Router are shielded against the
generation of radio interference in accordance with the application of Council Directive 89/336/EEC, Article 4a.
Conformity is declared by the application of EN 55 022 Class B (CISPR 22).
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Bestätigung des Herstellers/Importeurs
Es wird hiermit bestätigt, daß das Model RT328 ISDN Router und Model RH348 ISDN Router gemäß der im
BMPT-AmtsblVfg 243/1991 und Vfg 46/1992 aufgeführten Bestimmungen entstört ist. Das vorschriftsmäßige Betreiben
einiger Geräte (z.B. Testsender) kann jedoch gewissen Beschränkungen unterliegen. Lesen Sie dazu bitte die
Anmerkungen in der Betriebsanleitung.
Das Bundesamt für Zulassungen in der Telekommunikation wurde davon unterrichtet, daß dieses Gerät auf den Markt
gebracht wurde und es ist berechtigt, die Serie auf die Erfüllung der Vorschriften hin zu überprüfen.
Certificate of the Manufacturer/Importer
It is hereby certified that the Model RT328 ISDN Router and the Model RH348 ISDN Router have been suppressed
in accordance with the conditions set out in the BMPT-AmtsblVfg 243/1991 and Vfg 46/1992. The operation of some
equipment (for example, test transmitters) in accordance with the regulations may, however, be subject to certain
restrictions. Please refer to the notes in the operating instructions.
Federal Office for Telecommunications Approvals has been notified of the placing of this equipment on the market
and has been granted the right to test the series for compliance with the regulations.
VCCI-2 Statement
This equipment is in the 2nd Class category (information equipment to be used in a residential area or an adjacent area
thereto) and conforms to the standards set by the Voluntary Control Council for Interference by Data Processing
Equipment and Electronic Office Machines aimed at preventing radio interference in such residential areas.
When used near a radio or TV receiver, it may become the cause of radio interference.
Read instructions for correct handling.
Customer Support
For assistance with installing and configuring your NETGEAR system or with post-installation questions or problems,
contact your point of purchase representative.
To contact customer support or to purchase additional copies of this document and publications for other NETGEAR
products, you can contact NETGEAR at the following numbers:
• Phone:
Australia: 1800-787-638 Korea: 00308-11-0319
Austria: 00800-06384327 Netherlands: 0800-023-0981
Denmark: 808-82179 Norway: 800-12041
Canada: 1-888-NETGEAR Singapore: 001-800-1233-4566
Finland: 0800-111-036 Sweden: 0200-298-298
France: 0800-77-17-53 Switzerland: 00800-0638-4327
Germany: 00800-06384327 (00800-0-NETGEAR)
Hong Kong: 001-800-1233-4566 United States: 1-888-NETGEAR
Japan: 0120-66-5402 All Other Countries: +1 801-236-8499
(00800-0-NETGEAR) New Zealand: 00800-1233-4566
(00800-0-NETGEAR) United Kingdom: 020-7216-0014
World Wide W eb
NETGEAR maintains a World Wide Web Home Page that you can access at the universal resource locator (URL)
http://www.NETGEAR.com. A direct connection to the Internet and a Web browser such as Internet Explorer
or Netscape are required.
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Preface
Purpose ........................................................................................................................... xv
Audience ..........................................................................................................................xv
Conventions .....................................................................................................................xvi
Special Message Formats .........................................................................................xvi
Use of Enter, Type, and Press ...................................................................................xvi
Other Conventions ...................................................................................................xvii
Related Publications .......................................................................................................xvii
Contents
Chapter 1
Introduction
About the Router ............................................................................................................1-1
Features .........................................................................................................................1-1
Key Features ............................................................................................................1-2
ISDN Support ...........................................................................................................1-3
Multilink PPP Support ..............................................................................................1-3
TCP/IP Support ........................................................................................................1-4
IP Address Masquerading by Dynamic NAT+ ....................................................1-4
Automatic Configuration of Attached PCs by DHCP .........................................1-4
Security ....................................................................................................................1-4
Calling Line Identification ...................................................................................1-4
PAP and CHAP Authentication ..........................................................................1-5
Callback .............................................................................................................1-5
Management Support ..............................................................................................1-5
Basic Router Concepts ...................................................................................................1-6
What is a Router? ....................................................................................................1-6
Routing Information Protocol ....................................................................................1-6
IP Addresses and the Internet .................................................................................1-7
Netmask ................................................................................................................... 1-9
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Subnet Addressing .................................................................................................1-10
Private IP Addresses ..............................................................................................1-12
Single IP Address Operation Using NAT ................................................................1-13
Address Resolution Protocol ..................................................................................1-14
Domain Name Server ............................................................................................1-14
IP Configuration by DHCP .....................................................................................1-15
Chapter 2
Router Installation and Connection
Package Contents ..........................................................................................................2-1
ISDN Services Checklist .................................................................................................2-2
Network Checklist ...........................................................................................................2-3
Connecting the Router ....................................................................................................2-4
Connecting the Serial Cable (Optional) ....................................................................2-7
Connecting to the ISDN Port ....................................................................................2-7
Connecting the Ethernet Cable ................................................................................2-7
Using Twisted Pair LAN Cabling ........................................................................2-8
Using Coaxial or Fiber LAN Cabling ..................................................................2-8
Connecting to the Hub Ports in the Model RH348 Router .......................................2-8
Connecting a Telephone, Fax, or Modem .................................................................2-8
Connecting the Power Adapter ................................................................................2-8
Connecting for Configuration ..........................................................................................2-9
Connecting Through a Serial Port ............................................................................2-9
Connecting Through a T elnet Connection ................................................................2-9
Chapter 3
Router Configuration
Configuration Methods ...................................................................................................3-1
Powering on the Router ..................................................................................................3-2
Navigating the Manager .................................................................................................3-3
Manager Menu Summary ...............................................................................................3-5
General Setup Menu ......................................................................................................3-6
ISDN Menus ...................................................................................................................3-7
North American ISDN Menu ....................................................................................3-7
DSS1 ISDN Menu ....................................................................................................3-8
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Ethernet Setup .............................................................................................................3-11
General Setup Menu ..............................................................................................3-11
DHCP and TCP/IP Setup .......................................................................................3-12
Manager Password Setup ............................................................................................3-14
Chapter 4
Configuration for Internet Access
Information Checklist ......................................................................................................4-1
Internet Access Configuration ........................................................................................4-2
Configuration for Single User Account ............................................................................4-4
Chapter 5
Remote Node Configuration
Editing PPP Options .......................................................................................................5-4
Bandwidth on Demand ...................................................................................................5-6
Chapter 6
Dial-In Configuration
Default Dial-In Setup ......................................................................................................6-1
Dial-In Users Setup ........................................................................................................6-4
Chapter 7
TCP/IP Configuration
LAN-to-LAN Application ..................................................................................................7-1
Remote Node Setup .......................................................................................................7-2
Static Route Setup ..........................................................................................................7-4
Chapter 8
Filter Configuration
Router Filter Structure ....................................................................................................8-2
Configuring a Filter Set ...................................................................................................8-2
Configuring a Filter Rule .................................................................................................8-4
TCP/IP Filter Rule ....................................................................................................8-4
Generic Filter Rule ...................................................................................................8-7
Applying a Filter Set .......................................................................................................8-8
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Reducing Unnecessary Calls by Windows 95 ................................................................8-9
Diagnosing the Situation ..........................................................................................8-9
Implementing the Filter ...........................................................................................8-11
Applying the Filter ..................................................................................................8-14
Chapter 9
System Maintenance
System Status ................................................................................................................9-1
Terminal Baud Rate ........................................................................................................9-3
Log and Trace .................................................................................................................9-4
View Error Log .........................................................................................................9-4
Syslog and Accounting .............................................................................................9-4
Diagnostic Menu .............................................................................................................9-6
ISDN Tools ...............................................................................................................9-6
TCP/IP Tools ............................................................................................................9-7
System Tools ............................................................................................................9-8
Back Up Configuration ....................................................................................................9-8
Restore Configuration .....................................................................................................9-8
Software Update .............................................................................................................9-9
Command Interpreter Mode ...........................................................................................9-9
Call Control ...................................................................................................................9-10
Blacklist ..................................................................................................................9-10
Budget Management ..............................................................................................9-10
Call History .............................................................................................................9-11
Call Control Parameters .........................................................................................9-11
Chapter 10
Troubleshooting
Basic Functioning .........................................................................................................10-1
LEDS ...................................................................................................................... 10-1
Test LED .................................................................................................................10-2
LAN Link LED .........................................................................................................10-2
Troubleshooting the ISDN Line .....................................................................................10-2
ISDN Initialization or Reset ....................................................................................10-3
ISDN Loopback Test ...............................................................................................10-3
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Troubleshooting a TCP/IP Network Using a Ping Utility ...............................................10-4
Testing the LAN Path to Your Router ......................................................................10-4
Testing the Path from Your PC to a Remote Device ...............................................10-5
Troubleshooting a Remote Node or ISP Connection ....................................................10-5
Troubleshooting a Remote User Connection ................................................................10-6
Troubleshooting the Manager Interface ........................................................................10-7
Testing the Phone Ports ...............................................................................................10-7
Restoring the Default Configuration and Password ......................................................10-7
Appendix A
Technical Specifications
General Specification ....................................................................................................A-1
Appendix B
Ordering ISDN Lines
Ordering the Line ........................................................................................................... B-1
Provisioning for Switches in North America ................................................................... B-2
Provisioning for AT&T 5ESS Switch ........................................................................ B-2
Provisioning for Northern Telecom Switch .............................................................. B-4
Appendix C
ISDN Clearing Codes
Clearing Codes ..............................................................................................................C-1
Appendix D
Using the Protocol Analyzer and Trace Tools
The Diagnostic Process .................................................................................................D-1
ISDN Protocol Analyzer .................................................................................................D-2
Pack et Tracing ................................................................................................................ D-5
Packet Trace Display Format ...................................................................................D-8
Glossary
Index
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x Contents
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Figure 1-1. Three Main Address Classes ...................................................................1-8
Figure 1-2. Example of Subnetting a Class B Address ............................................1-10
Figure 1-3. Single IP Address Operation Using NAT ................................................1-13
Figure 2-1. Front Panel of Model RT328 Router ........................................................2-4
Figure 2-2. Front Panel of Model RH348 Router ........................................................2-4
Figure 2-3. Rear Panel of the Model RT328 Router ...................................................2-6
Figure 2-4. Rear Panel of the Model RH348 Router ..................................................2-6
Figures
Figure 3-1. Start-up Display .......................................................................................3-2
Figure 3-2. Manager Main Menu ................................................................................3-4
Figure 3-3. Menu 1 - General Setup ...........................................................................3-6
Figure 3-4. Menu 2 - ISDN Setup for North America .................................................3-8
Figure 3-5. Menu 2 - ISDN Setup for DSS1 .............................................................3-10
Figure 7-1. LAN-to-LAN Application ...........................................................................7-1
Figure 8-1. Outgoing Packet Filtering Process ...........................................................8-1
Figure 8-2. LAN Packet Which Triggered Last Call .....................................................8-9
Figure 8-3. Menu 21 Filter Set Configuration ...........................................................8-11
Figure 8-4. TCP/IP Filter Rule Menu ........................................................................8-12
Figure 8-5. Filter Rules Summary Menu ..................................................................8-13
Figure 8-6. Remote Node Profile Menu ....................................................................8-14
Figures xi
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Figure 9-1. Packet Examples .....................................................................................9-3
Figure 9-2. Trace Display for a Successful TCP/IP Protocol Connection ...................9-7
Figure 9-3. Trace Display for a Failed TCP/IP Protocol Connection ...........................9-7
Figure D-1. ISDN Protocol Analyzer Display ............................................................. D-4
Figure D-2. Trace Screen ........................................................................................... D-7
Figure D-3. Packet Trace Display Definitions ............................................................. D-8
Figure D-4. PPP Message Definitions ....................................................................... D-8
xii Figures
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Table 1-1. Netmask Notation Translation Table for One Octet ................................1-11
Table 1-2. Netmask Formats ...................................................................................1-12
Table 2-1. LED Descriptions .....................................................................................2-5
Table 3-1. Manager Menu Commands ....................................................................3-3
Table 3-2. Manager Menu Summary .......................................................................3-5
Table 3-3. ISDN Setup Menu Parameters for North America ..................................3-7
Table 3-4. ISDN Setup Field Descriptions ...............................................................3-9
Table 3-5. Ethernet General Setup Menu Fields ....................................................3-11
Table 3-6. Menu 3 - Ethernet Setup Menu Fields ..................................................3-12
Tables
Table 5-1. Menu 11.1 Remote Node Profile Fields ..................................................5-2
Table 5-2. Fields in Menu 11.2 - Remote Node PPP Options ..................................5-5
Table 5-3. Relationship Between BTR and MTR ......................................................5-6
Table 6-1. Fields in Menu 13 - Default Dial-in Setup ...............................................6-2
Table 6-2. Fields in Menu 14.1 - Edit Dial-in User ...................................................6-5
Table 7-1. Fields in Menu 11.1 - Remote Node Profile Fields .................................7-2
Table 7-2. Menu 11.3 Remote Node Network Layer Options Fields ........................7-3
Table 7-3. Edit IP Static Route Menu Fields ............................................................7-5
Table 8-1. Abbreviations Used in Menu 21.1 - Filter Rules Summary .....................8-3
Table 8-2. Abbreviations Used if Filter Type Is IP .....................................................8-3
Table 8-3. Abbreviations Used if Filter Type Is GEN .................................................8-4
Table 8-4. TCP/IP Filter Rule Menu Fields ..............................................................8-5
Table 8-5. Generic Filter Rule Menu Fields .............................................................8-7
Tables xiii
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Table 9-1. System Maintenance Status Menu Fields ................................................9-1
Table 9-2. System Maintenance Status Menu Fields ...............................................9-2
Table 9-3. System Maintenance - Log and Trace Menu Fields .................................9-4
Table 9-4. System Maintenance - Syslog and Accounting Menu Fields ...................9-5
Table 9-5. System Maintenance - Diagnostic Menu Fields .......................................9-6
Table 10-1. Code Numbers for Failed ISDN Initialization ..........................................10-3
Table B-1. Switch Types Supported ........................................................................ B-2
Table B-2. Provisioning Features and Settings for National ISDN-1 Services ........ B-3
Table B-3. Provisioning Features and Settings for Multipoint Service ..................... B-3
Table B-4. Provisioning Features and Settings for Point-to-Point Service ............... B-4
Table B-5. Provisioning Features and Settings for National ISDN-1 Service .......... B-5
Table B-6. Provisioning Features and Settings for Custom ISDN Service ............... B-5
Table C-1. ISDN Call Clearing Codes ..................................................................... C-1
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Preface
Congratulations on your purchase of the NETGEAR
RH348 ISDN Router.
These ISDN router models provide connection for one or more computer workstations to the
Internet or to the office over Integrated Services Digital Network (ISDN) lines. They operate at a
speed of up to 512 kilobits per second (Kbps) or 128 Kbps without compression. At these speeds,
you can download video clips, music, or high-resolution color graphics from the World Wide Web
or other online services many times faster than you can with an analog modem. The routers
support concurrent data and voice communications, reducing cost and administration of multiple
phone lines.
™
Model RT328 ISDN Router or Model
Purpose
This guide describes the features of the Model RT328 router and the Model RH348 router and
provides installation and configuration instructions. When discussing features, functions, or
specifications that apply to both router models, the guide refers to the Model RT328/RH348 router.
Audience
To configure and install the Model RT328/RH348 router, you should have the following
background and experience:
• Working knowledge of basic network management concepts and terminology
• Working knowledge of tools and procedures for installing and operating sensitive electronic
equipment
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Reference Guide for the Model RT328 and Model RH348 ISDN Routers
Conventions
This section describes the conventions used in this guide.
Special Message Formats
This guide uses the following formats to highlight special messages:
This format is used to highlight information of importance or special interest.
Note:
Caution:
equipment failure or loss of data.
Warning:
equipment damage.
Danger:
mishandling equipment.
This format is used to highlight information that will help you prevent
This format is used to highlight information about the possibility of injury or
This format is used to alert you that you may incur an electrical shock by
Use of Enter, Type, and Press
This guide uses “enter,” “type,” and “press” to describe the following actions:
• When you read “enter,” type the text and press the Enter key.
• When you read “type,” type the text, but do not press the Enter key.
• When you read “press,” press only the alphanumeric or named key.
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Reference Guide for the Model RT328 and Model RH348 ISDN Routers
Other Conventions
This guide uses the following typographical conventions:
italics
courier font
Book titles and UNIX file, command, and directory names.
Screen text, user-typed command-line entries.
Initial Caps Menu titles and window and button names.
[Enter] Named keys in text are shown enclosed in square brackets. The notation
[Enter] is used for the Enter key and the Return key.
[Ctrl]+C Two or more keys that must be pressed simultaneously are shown in text
linked with a plus (+) sign.
ALL CAPS DOS file and directory names.
Related Publications
For more information about configuring the Model RT328/RH348 router using FirstGear
configuration software, refer to Getting Started Using FirstGear for the Model RT328 and Model
RH348 ISDN Routers (part number M1-RH348NA-0).
For more information about address assignment, refer to RFC 1597, Address Allocation for
Private Internets, and RFC 1466, Guidelines for Management of IP Address Space .
For more information about IP address translation, refer to RFC 1631, The IP Network Address
Tr anslator (NAT) .
™
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Intro.fm Page 1 Tuesday, October 10, 2000 3:15 PM
This chapter describes the features of the NETGEAR Model RT328 ISDN Router and Model
RH348 ISDN Router and discusses planning considerations for installation.
Chapter 1
Introduction
About the Router
The Model RT328/RH348 router transports data from one local area network (LAN) to another
through a wide area network (WAN) connection.
The router compares the network addresses of data packets sent through the LAN to the entries in
its address tables. If a match is found for a destination network, the router passes the packet to the
path indicated by the entry in the routing table.
The entry in the path list contains the ISDN phone number(s) of the target router. The router sends
the number to the ISDN port for the call to be connected. The WAN path is established, and the
data is sent to the remote unit. At the receiving end, the process operates in the reverse order, from
the ISDN port to the LAN port.
Features
The Model RT328/RH348 router is a flexible, high-performance, easy-to-use router that provides a
cost-effective solution for intelligent networking access across an ISDN line. With minimum
setup, you can install and use the router within minutes to meet a wide variety of networking
requirements.
Introduction 1-1
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Reference Guide for the Model RT328 and Model RH348 ISDN Routers
Key Features
The Model RT328/RH348 router provides the following features:
• Standard basic rate ISDN (BRI) connection
– ISDN, 2B+D, providing two 64 Kbps data channels and a 16 Kbps control channel
– Four-wire S/T interface on Model RT328-S/RH348-S router
– Two-wire U interface on Model RT328-U/RH348-U router
– Two-wire NTT interface on Model RH348-D router
• Protocol Support
– IP routing
– Multilink Point-to-Point Protocol (PPP) for 128 Kbps operation
– Dynamic bandwidth-on-demand with BACP
– Dynamic NAT+ for operation with a single static or dynamic IP address
– DHCP for dynamically assigning network configuration information to LAN
workstations
• Industry-standard compression
– Hi/fn (Stac LZS) compression with CCP
• Easy installation and management
– FirstGear graphical user interface (GUI) management software for Windows
– Built-in Manager interface for Macintosh, UNIX, and PC users, accessible by
terminal or Telnet Protocol
– Configurable through the LAN—no serial connection required
• Security
– Access control on management functions
– Dial-in access control by Calling Line Identification (CLID) and Callback
– PAP and CHAP authentication support
®
users
1-2 Introduction
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Reference Guide for the Model RT328 and Model RH348 ISDN Routers
• Twisted pair and AUI Ethernet ports (Model RT328 router only)
– RJ-45 interface allowing connection to a 10BASE-T network
– AUI interface allowing connection to a coaxial or fiber network using a transceiver
• Four-port twisted pair Ethernet hub (Model RH348 router only)
– Four RJ-45 interfaces for connection to 10BASE-T workstations
• Analog voice ports
– Provides two RJ-11 interfaces
– Allows a standard analog PSTN device (for example, telephone, fax, or modem) to
make and receive calls from other ISDN or PSTN connected devices
– Eliminates the need for a separate PSTN line in a SOHO (small office/home office)
environment
• Eleven LEDs for easy monitoring of status and activity
• Flash EPROM for firmware upgrade
• Five-year warranty
• Free technical support seven days a week, twenty-four hours a day
ISDN Support
The Model RT328/RH348 router is designed to take advantage of Integrated Services Digital
Network (ISDN) for transmission of data over digital telephone networks. A basic rate interface
(BRI), which is the usual ISDN implementation, consists of two 64 kilobit per second (Kbps)
B channels for data and one 16 Kbps D channel for control information.
One advantage of using ISDN to connect routers is that the connection is set up only if there is data
to be sent to the remote network. The router sets up a call, transfers the data, and then hangs up
automatically when the connection is no longer needed.
Multilink PPP Support
When the single-channel ISDN line utilization exceeds a configurable threshold, the router can
automatically establish an additional ISDN call to provide additional bandwidth. During heavy
traffic, the two 64 Kbps B channels are combined using Multilink PPP to provide a fast 128 Kbps
pipe. When traffic slows down, one of the B channels is idled to save toll charges. The router also
reverts back to one B channel for data when an analog port is used.
Introduction 1-3
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Reference Guide for the Model RT328 and Model RH348 ISDN Routers
TCP/IP Support
The Model RT328/RH348 router supports the Transmission Control Protocol/Internet Protocol
(TCP/IP) and Routing Information Protocol (RIP), which ensures that ISDN connections are
established only when passing data.
For further information about TCP/IP, refer to “Basic Router Concepts” on page 1-6.
IP Address Masquerading by Dynamic NAT+
Both NETGEAR routers allow an entire department of networked PCs to share an Internet account
using only a single IP address, which may be statically or dynamically assigned by your Internet
service provider (ISP). This technique, an extension of network address translation (NAT), is
known as IP address masquerading and typically allows the use of a very inexpensive ISP account.
Automatic Configuration of Attached PCs by DHCP
The routers can dynamically assign network configuration information, including IP, gateway, and
domain name server (DNS) addresses, to attached PCs on the LAN using the Dynamic Host
Configuration Protocol (DHCP). This feature greatly simplifies configuration of LAN-attached
workstations.
Security
The Model RT328/RH348 router is equipped with several features designed to maintain security.
These security features are described in this section.
Calling Line Identification
The use of Calling Line Identification (CLID or Caller ID) ensures that incoming ISDN calling
numbers are checked against known numbers before a call is answered and access is granted,
thus providing a first level of security. In many areas, you must specifically request that CLID
be enabled by the telephone company for your ISDN line. In some regions, CLID may not be
available.
1-4 Introduction
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Reference Guide for the Model RT328 and Model RH348 ISDN Routers
PAP and CHAP Authentication
For connecting to other routers, the Model RT328/RH348 router supports two authentication
protocols: Password Authentication Protocol (PAP) and Challenge Handshake Authentication
Protocol (CHAP). PAP sends the user name and password in plain text. CHAP scrambles the
password before it is sent over the wire. Although CHAP provides better security, PAP is readily
available on more platforms.
Callback
For security and simplified cost accounting, the router implements Callback. When a remote user
dials in, the router can disconnect the call and call the user back, so that any further call charges
are incurred by the location of the router. The caller can provide the callback numbers; or, for
security, the router can be programmed to call back a predetermined number.
Management Support
The router is designed to be installed and made operational within minutes after connection to the
network.
If you are a PC user, the FirstGear software lets you easily configure the unit from the Windows
environment.
If you are a Macintosh, UNIX, or PC user, you can connect to the built-in Manager interface,
which can be accessed through a terminal connected to the MGR (manager) port or through a
Telnet session across the network. The built-in Manager interface manages and configures the
unit through an easily understood screen process.
Introduction 1-5
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Reference Guide for the Model RT328 and Model RH348 ISDN Routers
Basic Router Concepts
In general, the cost of providing network bandwidth is proportional to the data speed and the
distance over which the network extends. Large amounts of bandwidth are provided easily and
relatively inexpensively in a local area network (office, department, and similar situations).
However, providing the same high data speeds between two local networks that are physically
distant may be prohibitively expensive. Because of this expense, high-speed local area networks
(LANs) are usually interconnected by slower-speed links to form a wide area network (WAN).
In order to make the best use of the slower WAN links, a mechanism must be in place at each
location for selecting data meant only for another location and sending it by the best available link.
The function of selecting and forwarding this data is performed by a router.
What is a Router?
A router is a device that forwards traffic between networks based on network layer information in
the data and on routing tables maintained by the router. In these routing tables, a router builds up a
logical picture of the overall network by gathering and exchanging information with other routers
in the network. Using this information, it chooses the best path for forwarding network traffic.
Routers vary in performance and scale, number of routing protocols supported, and types of
physical WAN connections supported. The Model RT328/RH348 router is a small office router
that routes the IP protocol over a dial-up ISDN connection.
Routing Information Protocol
One of the protocols used by a router to build and maintain a picture of the network is the Routing
Information Protocol (RIP). RIP is a distance vector protocol, meaning that all the decisions about
which path to use are based upon a logical distance between source and destination networks. This
distance is measured in “hops,” meaning the number of relaying routers in the path between the
source LAN router and the router of the destination LAN. For example, the LAN of router A is
considered to be 1 hop away. If router A can reach the network of router B by a direct WAN link to
the network of router B, the network of router B is two hops away. If another network must be
reached by calling router B and having router B forward the data, that network is n hops away,
where n is the number of routers traversed by the data to get to the network farthest away. When
there are multiple paths to a network, the path with the fewest number of hops is chosen and is
regarded as the best path, and all other information about how to get to that network is discarded.
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Using RIP, routers update one another periodically and check to see if there are any changes to be
added to the routing table. An important consideration is the convergence time, or how long it
takes for a change to the routing topology (such as a new node or a node failure), to be propagated
throughout the entire RIP environment. To prevent this convergence process from being
excessively long, RIP is limited to 15 hops maximum.
The Model RT328/RH348 router supports both the older RIP-1 and the newer RIP-2 protocols.
Among other improvements, RIP-2 supports subnetting and multicasting.
IP Addresses and the Internet
Because TCP/IP networks are interconnected widely across the world, every machine on the
Internet must have a unique address to make sure that transmitted data reaches the correct
destination. Blocks of addresses are assigned to organizations by the Internet Assigned Numbers
Authority (IANA). Individual users and small organizations may obtain their addresses either from
the IANA or from an Internet service provider (ISP).
The Internet Protocol (IP) uses a 32-bit address structure. The address is usually written in dot
notation (also called dotted-decimal notation), in which each group of eight bits is written in
decimal form, separated by decimal points. For example, the binary address:
11000011 00100010 00001100 00000111
is normally written as:
195.34.12.7
which is easier to remember and easier to enter into your computer.
In addition, the 32 bits of the address are subdivided into two parts. The first part of the address
identifies the network, and the second part identifies the host node or station on the network. The
dividing point may vary depending on the address range and the application.
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There are five standard classes of IP addresses. These address classes have different ways of
determining the network and host sections of the address, allowing for different numbers of hosts
on a network. Each address type begins with a unique bit pattern, which is used by the TCP/IP
software to identify the address class. After the address class has been determined, the software
can correctly identify the host section of the address. The three main address classes are illustrated
in Figure 1-1, which shows the network and host sections of the address for each address type.
Class A
Network Node
Class B
Network Node
Class C
Network Node
7261
Figure 1-1. Three Main Address Classes
Class A addresses can have up to 16,777,214 hosts on a single network. They use an 8-bit network
number and a 24-bit node number. Class A addresses are in this range:
1.x.x.x to 126.x.x.x.
Class B addresses can have up to 65,354 hosts on a network. A Class B address uses a 16-bit
network number and a 16-bit node number. Class B addresses are in this range:
128.1.x.x to 191.254.x.x.
Class C addresses can have 254 hosts on a network. Class C addresses use 24 bits for the network
address and 8 bits for the node. They are in this range:
192.0.1.x to 223.255.254.x.
Class D addresses are used for multicasts (messages sent to many hosts). Class D addresses are in
this range:
224.0.0.0 to 239.255.255.255.
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Class E addresses are for experimental use.
This addressing structure allows IP to uniquely identify each physical network and each node on
each physical network.
For each unique value of the network portion of the address, the base address of the range (host
address of all zeros) is known as the network address and is not usually assigned to a host. Also,
the top address of the range (host address of all ones) is not assigned but is used as the broadcast
address for sending a packet simultaneously to all hosts with the same network address.
Netmask
In each of the above address classes, the size of the two parts (network address and host address)
is implied by the class. This partitioning scheme can also be expressed by a netmask associated
with the IP address. A netmask is a 32-bit quantity that, when logically ANDed with an IP address,
yields the network address. For instance, the netmasks for Class A, B, and C addresses are
255.0.0.0, 255.255.0.0, and 255.255.255.0, respectively.
For example, the address 192.168.170.237 is a Class C IP address whose network portion is the
upper 24 bits. When ANDed with the Class C netmask, as shown here, only the network portion of
the address remains:
11000000 10101000 10101010 11101101 (192.168.170.237)
ANDed with:
11111111 11111111 11111111 00000000 (255.255.255.0)
Equals:
11000000 10101000 10101010 00000000 (192.168.170.0)
As a shorter alternative to dotted-decimal notation, the netmask may also be expressed in terms of
the number of ones from the left. This number is appended to the IP address, following a backward
slash ( / ), as “/n.” In the example, the address could be written as 192.168.170.237/24, indicating
that the netmask is 24 ones followed by 8 zeros.
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Subnet Addressing
By looking at the addressing structures, you can see that even with a Class C address, there are a
large number of hosts per network. Such a structure is an inefficient use of addresses if each end of
a routed link requires a different network number. It is unlikely that the smaller office LANs would
have that many devices. You can resolve this problem by using a technique known as subnet
addressing.
Subnet addressing allows us to split one IP network address into smaller multiple physical
networks known as subnetworks. Some of the node numbers are used as a subnet number instead.
A Class B address gives us 16 bits of node numbers translating to 64,000 nodes. Most
organizations do not use 64,000 nodes, so there are free bits that can be reassigned. Subnet
addressing makes use of those bits that are free, as illustrated in Figure 1-2.
Class B
Network Subnet Node
7262
Figure 1-2. Example of Subnetting a Class B Address
A Class B address can be effectively translated into multiple Class C addresses. For example, the
IP address of 172.16.0.0 is assigned, but node addresses are limited to 255 maximum, allowing
8 extra bits to use as a subnet address. The IP address of 172.16.97.235 would be interpreted as
IP network address 172.16, subnet number 97, and node number 235. In addition to extending
the number of addresses available, subnet addressing provides other benefits. Subnet addressing
allows a network manager to construct an address scheme for the network by using different
subnets for other geographical locations in the network or for other departments in the
organization.
Although the preceding example uses the entire third octet for a subnet address, note that you are
not restricted to octet boundaries in subnetting. To create more network numbers, you need only
shift some bits from the host address to the network address. For instance, to partition a Class C
network number (192.68.135.0) into two, you shift 1 bit from the host address to the network
address. The new netmask (or subnet mask) is 255.255.255.128. The first subnet has network
number 192.68.135.0 with hosts 192.68.135.1 to 129.68.135.126, and the second subnet has
network number 192.68.135.128 with hosts 192.68.135.129 to 192.68.135.254.
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The number 192.68.135.127 is not assigned because it is the broadcast address
Note:
of the first subnet. And 192.68.135.128 is not assigned because it is the network address
of the second subnet.
Table 1-1 lists the additional subnet mask bits in dotted-decimal notation. To use the table, write
down the original class netmask and replace the 0 value octets with the dotted-decimal value of the
additional subnet bits. For instance, to partition your Class C network 204.247.203.0 with subnet
mask 255.255.255.0 into 16 subnets (4 bits), the new subnet mask becomes 255.255.255.240.
Table 1-1. Netmask Notation Translation Table for One Octet
Number of Bits
1 128
2 192
3 224
4 240
5 248
6 252
7 254
8 255
Dotted-Decimal Value
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Table 1-2 displays several common netmask values in both the dotted-decimal and the
masklength formats.
Table 1-2. Netmask Formats
Dotted-Decimal Masklength
255.0.0.0 /8
255.255.0.0 /16
255.255.255.0 /24
255.255.255.128 /25
255.255.255.192 /26
255.255.255.224 /27
255.255.255.240 /28
255.255.255.248 /29
255.255.255.252 /30
255.255.255.254 /31
255.255.255.254 /32
NETGEAR strongly advises that all hosts on a LAN segment use the same netmask for the
following reasons:
• So that hosts recognize local IP broadcast packets
When a device broadcasts to its segment neighbors, it uses a destination address of the local
network address with all ones for the host address. In order for this scheme to work, all devices
on the segment must agree on which bits comprise the host address.
• So that a local router or bridge will know which addresses are local and which are remote
Private IP Addresses
If your networks are isolated from the Internet (for example, only between your two branch
offices), you can assign any IP addresses to the hosts without problems. However, the IANA has
reserved the following three blocks of IP addresses specifically for private networks:
10.0.0.0 - 10.255.255.255
172.16.0.0 - 172.31.255.255
192.168.0.0 - 192.168.255.255
NETGEAR recommends that you choose your private network number from this list.
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