Cisco uBR7200 Troubleshooting

Download

CHAPTER

Troubleshooting the System

This chapter contains troubleshooting information. The chapter includes the following sections:

• Using a Cable Modem at the Headend to Verify Downstream Signals

• Managing Cable Modems on the HFC Network

• Polling Cable Modems

• Understanding Show Command Responses

• Troubleshooting Using Cable Flap Lists

• Performing Amplitude Averaging

• Setting Downstream Test Signals

• Pinging Unresponsive Cable Modems

• Using Cable Interface Debug Commands

• Managing the Cisco uBR7246 VXR Clock Card

Using a Cable Modem at the Headend to Verify Downstream Signals

You can use a Cisco uBR924 cable access router to verify the downstream signal originating from a Cisco uBR7200 series universalbroadband router. Be sure you configure the Cisco uBR924 according to DOCSIS cable modem practises. To verify the downstream signal from a Cisco uBR7200 series universal router using a Cisco uBR924, follow the procedure below:

Step 1 After the Cisco uBR924 is operational and you have an input signal between 0 and +5 dBmV, enter the

show controller c0 tuner command.

Step 2 Scan the output for the value corresponding to the signal to noise (SNR) estimate variable. If this value

is at least 35 dB, then you have an optimized signal. If the value is less than 34 dB, adjust the upconverter at the cable headend.

Cisco uBR7200 Series Universal Broadband Router Software Configuration Guide

78-5897-01

4-1

Chapter 4 Troubleshooting the System

Managing Cable Modems on the HFC Network

Tips The SNR estimate for a cable modem installed at a headend should be between 35 dB and

39 dB. Although the exact value displayed will vary from cable modem to cable modem, values collected on the same cable modem from measurement to measurement will be consistent. Maximizing SNR optimizes cable modem reliability and service quality.

Managing Cable Modems on the HFC Network

To manage cable modems connected to the network, perform the following as appropriate:

• Configure Sync Message Interval

• Activate Cable Modem Authentication

• Activate Cable Modem Upstream Address Verification

• Configure Dynamic Contention Algorithms (Cable Insertion Interval, Range, and Data Backoffs)

• Configure the Dynamic Map Advance Algorithm

• Configure Per Modem Filters

• Configure the Maximum Number of Hosts Attached to a Cable Modem

• Configure Cable Modem Registration Timeout

• Clear Cable Modem Reset

• Clear Cable Modem Counters

• Configure Traffic Shaping

• Configure Spectrum Management (without the Cisco MC16S Cable Modem Card)

Caution Cisco recommends using default values for most commands. Default settings are adequate

for most systems.

Configure Sync Message Interval

To specify the interval between successive sync message transmissions from the Cisco uBR7200 series, use the following command in cable interface configuration mode.

Table 4-1 Instructions to Conﬁgure Sync Message Interval

Command Purpose

CMTS01(config-if)#cable sync-interval

no cable sync-interval

msec

Specify the interval in milliseconds between successive sync message transmissions from the Cisco uBR7200 series. Valid values are from 1 to 200 msec. Default = 10 msec.

Return the sync message interval to its default value of 10 msec.

4-2

Cisco uBR7200 Series Universal Broadband Router Software Configuration Guide

78-5897-01

Chapter 4 Troubleshooting the System

Verify Sync Message Interval

To verify whether or not a sync message interval is configured, enter the show running-config command and look for the cable interface configuration information. If the sync message interval is deactivated or reset to its default value, the no sync interval command line appears in the output.

Activate Cable Modem Authentication

The Cisco uBR7200 series can be configured to require all cable modems to return a known text string to register with the CMTS and gain access to the network. The text string can be from 1 to 80 characters in length. To activate cable modem authentication, use the following command from cable interface configuration mode.

Table 4-2 Instructions to Activate Cable Modem Authentication

Command Purpose

CMTS01(config-if)# cable shared-secret authorization-key

[0|7]

Enable cable modem authentication: 0 specifies an unencrypted authentication key; 7 specifies an encrypted authentication key.

Managing Cable Modems on the HFC Network

CMTS01(config-if)# no cable shared-secret

Tips Be sure you enter the correct slot and port number in the cable interface configuration

mode. Verify that the cable modem is using BPI and that it is assigned to a QoS with privacy active. Verify that the cable modem configuration file contains a matching key.

Disable cable modem authentication.

Verify Cable Modem Authentication

To verify whether cable modem authentication is activated or deactivated, enter the command more system:running-config and look for the cable interface configuration information. If cable modem

authentication is deactivated, it appears in this output as no cable secret-shared.

Activate Cable Modem Upstream Address Verification

Cable modem upstream address verification ensures that only cable modems that have received DHCP leases through the Cisco uBR7200 series can access the HFC network. The Cisco uBR7200 series discards all packets received from or for hosts that have not received DHCP-assigned addresses.

78-5897-01

Cisco uBR7200 Series Universal Broadband Router Software Configuration Guide

4-3

Managing Cable Modems on the HFC Network

To activatecable modem upstream address verification, use the following cable interface configuration command.

Table 4-3 Instructions to Activate Cable Modem Upstream Address Veriﬁcation

Command Purpose

CMTS01(config-if)# cable source-verify

[dhcp]

Activate cable modem upstream verification. The dhcp option specifies that queries be sent to verify unknown IP addresses in upstream data packets.

Chapter 4 Troubleshooting the System

CMTS01(config-if)# no cable source-verify

Return to the default upstream verification state.

Verify Cable Modem Upstream Address Verification

To verify whether cable modem upstream verification is activated or deactivated, enter the command more system:running-config and look for the no cable source-verify notation in the cable interface configuration information.

Tips Be sure you enter the correct slot and port number when you enter the cable interface

configuration mode.

Note If the Cisco uBR7200 series is reloaded or the ARP table is cleared, all hosts on the

network will be forced to release and renew their IP addresses. Some systems may require restarting if the IP protocol stack is unable to renew using a broadcast IP address.

Configure Dynamic Contention Algorithms (Cable Insertion Interval, Range, and Data Backoffs)

The Cisco uBR7200 series universal broadband router software includes:

• An algorithm that dynamically controls the rate of upstream contention slots —initial ranging and

bandwidth-requests.

• An algorithm that varies backoff parameters CMs use within each of the initial ranging and

bandwidth-request upstream contention subchannels.

These algorithms control the capacity of the contention subchannel and how efficiently a given contention subchannel capacity is utilized.

In high contention mode, the Cisco uBR7200 seriesMACschedulerusescollisionstatistics and sustains a high frequency of initial ranging slots until it detects a steady ranging state. The CMTS dynamically varies the frequency of initial ranging slots using the data grant utilization on the upstream channel(s). The CMTS trades upstream bandwidth between data grants and initial ranging slots. The CMTS auto-detects a high collision state and switches to low insertion interval mode after a steady state is achieved where few collisions occur.

The CMTS is careful when monitoring the ranging channel health to revert to a steady state. In steady state mode, data grants—grant utilization—receive preference over initial ranging slots.

4-4

Cisco uBR7200 Series Universal Broadband Router Software Configuration Guide

78-5897-01

Chapter 4 Troubleshooting the System

Although the binary exponential backoff algorithm operates in a distributed fashion at different CMs, the CMTS provides centralized control for the backoff algorithm. To achieve this, it remotely monitors traffic load—the backlog developing on the contention channel—and then varies the backoff start and end specified in the MAPs for that upstream channel. This ensures colliding CMs are properly randomized in time.

The following cable interface commands are available to configure the dynamic contention algorithms:

[no] cable insertion-interval [ [no] cable upstream < [no] cable upstream <

Tips System defaults are to have dynamic ranging interval enabled, dynamic ranging backoff

enabled, and fixed data backoffs for each upstream of a cable interface.

The default automatic insertion interval setting enables the Cisco automatic initial ranging period algorithm where lower and upper default values of 50 msecs and 2 secs are used. The default automatic range-backoff enables the dynamic backoff algorithm.

To deviate from system defaults, use one of the following commands in cable interface configuration mode.

port num port num

automatic[<Imin[Imax

> range-backoff [ > data-backoff [

automatic

Managing Cable Modems on the HFC Network

]>]] | [<

] | [<

msecs

start

> <

end

Table 4-4 Instructions to Modify Dynamic Contention Algorithm Defaults

Command Purpose

CMTS01(config-if)#

automatic

[no]

cable insertion-interval

Disable or enable the dynamic ranging interval algorithm. If lower and upper bounds for varying the period are not specified,thesystem uses default values of 50 msecs and 2 secs respectively.

CMTS01(config-if)# cable insertion-interval automatic min

<25-2000>

CMTS01(config-if)# cable insertion-interval max

<500-2000>

CMTS01(config-if)# no cable insertion-interval

Set the lower bound on the initial ranging period for the auto ranging algorithm.

Set the upper bound on initial ranging period for the auto ranging algorithm.

Reset fixed initial ranging period to default value of 500 msecs. Also invokes fixed initial ranging algorithm.

CMTS01(config-if)# cable insertion-interval

<100-2000>

Enabled fixed initial ranging period algorithm with specified fixed period (msecs).

Configure the Dynamic Map Advance Algorithm

A CMTS administrator can enhance the upstream throughput from a cable modem connected to the Cisco uBR7200 series. The system employs a new algorithm that auto tunes the lookahead time in MAPs based on several input parameters for the corresponding upstream channel. The use of dynamic/optimal lookahead time in MAPs significantlyimprovesthe per-modem upstream throughput.

Cisco uBR7200 Series Universal Broadband Router Software Configuration Guide

78-5897-01

4-5

Managing Cable Modems on the HFC Network

Caution Only a trained CMTS administrator should adjust these values.

To configure the dynamic map advance algorithm, use the following command in cable interface configuration mode.

Table 4-5 Instructions to Conﬁgure the Dynamic Map Advance Algorithm

Command Purpose

CMTS01(config-if)#cable map-advance dynamic

[<n>]

| static

Specify a value to enhance the upstream throughput from a cable modem connected to the Cisco uBR7200 series. The <n> parameter provides the safety factor for the dynamic map advance algorithm. This parameter is specified in usecs and controls the amount of extra lookahead time in MAPs to account for inaccuracies of the measurement system and software latencies. The default value is 1000 usecs.

You can vary this between 500 to 1500 usecs. This parameter is a delta value added to the dynamic map-advance that the algorithm computes. Using larger safety factors increases the run time lookahead in MAPs, but reduces the upstream performance.

Use the static keyword for the map advance command. The Cisco uBR7200 series will use a fixed lookahead time in MAPs, regardless of the real propagation delay of the farthest cable modem on the network. This fixed lookahead time is computed based on the worst case parameters such as farthest DOCSIS propagation delay for the CMs.

Chapter 4 Troubleshooting the System

Caution Cisco recommends if you are adjusting the dynamic map advance algorithm that you do

not reduce the safety factor below the default value of 1000 usecs in a production network until you are confident that the reduced safety factor suffices for your deployment. The default value is chosen to be a safe operating point for the algorithm.

Configure Per Modem Filters

You can configure the Cisco uBR7200 series to filter incoming packets from individual hosts or cable modems based on the source Media Access Controller (MAC) or Internet Protocol (IP) address. Definition of filters follows standard Cisco IOS configuration practices for access lists and groups.

Note Configuring per modem or host filters is supported in Cisco IOS Release 12.0(5)T1 or

higher, as well as in Cisco IOS Release 12.0(6)SC or higher.

Cisco uBR7200 Series Universal Broadband Router Software Configuration Guide

4-6

78-5897-01

Chapter 4 Troubleshooting the System

To configure per modem filters, use the following commands in cable interface configuration mode.

Table 4-6 Instructions to Conﬁgure Per Modem Filters

Command Purpose

CMTS01(config-if)# cable {modem | host | device}

{<macaddr><ipaddr> | }

access group

<acl>

Configure access lists to be specified on a per-interface and per-direction basis. The packets receivedfrom cable modems and/or individual hosts are filteredbased on the cable modem or the host the packets are received from. Use modem if the device is a cable modem. Use host if the device is a CPE device attached to a cable modem.

Define the filter to be applied to the device and a given address. The macaddr specifies the cable modem’s or CPE device’s unique MAC address.

Use the ipaddr option to specify the CM or CPE device’s current IP address.

Use the acl option to assign the CM or CPE device to an access list. This defines the per-CM or per-host filterrequirementsimplementedattheCMTS,rather than at the CM. Access list numbers are 1 to 99 for fast IP access lists, 100 to 199 for show extended IP access lists.

Managing Cable Modems on the HFC Network

Note Access list numbers of 700 to

799 do not apply.

Caution The system applies filters after the cable modem registers with the CMTS. Filter

definitions are not saved across system reboots and must be applied each time a CM registers.

The software supports traps to alert CMTS administrators on CMs going offline or back online. A typical registration and login procedure is shown below:

1. The CM registers with the Cisco uBR7200 series.

2. The Cisco uBR7200 series sends traps to management systems in use for the network.

3. The management system sets per modem filters using SNMP or rsh.

4. The user logs in at the server.

5. The login server obtains required modem and CPE information from the Cisco uBR7200 series.

6. The login server sets per-CPE filter in the Cisco uBR7200 series. The per-CPE filter overrides the

per modem filter settings.

7. If the CM goes offline for a brief period of time, filters defined using the Cisco uBR7200 series

remain active. If a CM stays offline for more than 24 hours, filter settings are reset.

8. If the user logs out or the login server detects that the user is not online, the login server sets default

filters for the CM or the CPE device.

78-5897-01

Cisco uBR7200 Series Universal Broadband Router Software Configuration Guide

4-7

Chapter 4 Troubleshooting the System

Managing Cable Modems on the HFC Network

Configure the Maximum Number of Hosts Attached to a Cable Modem

To specify the maximum number of hosts that can be attached to a subscriber’s cable modem, use the following command in cable interface configuration mode.

Table 4-7 Instructions to Conﬁgure the Maximum Number of Hosts Attached to a Cable Modem

Command Purpose

CMTS01(config-if)# cable max-hosts

Specify the maximum number of hosts that can be attached to a cable modem on this interface. Valid range is from 0 to 255 hosts. Default = 0.

CMTS01(config-if)# no cable max-hosts

Reset the allowable number of hosts attached to a cable modem to the default value of 0 hosts.

Configure Cable Modem Registration Timeout

By default, registered cable modems that have no upstream activity for three minutes are timed out and disconnected from the Cisco uBR7200 series. This timeout interval can be decreased to 2 minutes or increased up to 60 minutes.

To specify the registration timeout interval for cable modems connected to the Cisco uBR7200 series, use the following command in cable interface configuration mode.

Table 4-8 Instructions to Conﬁgure Cable Modem Registration Timeout

Command Purpose

CMTS01(config-if)# cable registration-timeout

Specify the maximum number of minutes allowedto elapse with no upstream activity before terminating the connection. Valid range is from 2 to 60 minutes. Default = 3 minutes.

Clear Cable Modem Reset

4-8

To remove a single cable modem (or all cable modems) from the station maintenance list and reset the cable modem (or all cable modems) on the network, use one of the following commands in cable interface configuration mode.

Cisco uBR7200 Series Universal Broadband Router Software Configuration Guide

78-5897-01

Chapter 4 Troubleshooting the System

Table 4-9 Instructions to Clear Cable Modem Reset

Command Purpose

CMTS01(config-if)# clear cable modem

mac-addr

reset

Removethecablemodem with a specificMACaddress from the station maintenance list and reset it.

Managing Cable Modems on the HFC Network

CMTS01(config-if)# clear cable modem

CMTS01(config-if)# clear cable modem all reset

ip-addr

Verify Clear Cable Modem Reset

To verify whether or not the clear cable modem reset command has removed a cable modem from the station maintenance list and forced it to start a reset sequence, enter the show cable modem command.

Tips Be sure you entered the correct cable modem IP address or MAC address when you typed

the command. It might take up to 30 seconds for the cable modem to start the reset sequence.

Note This command is useful if an SNMP manager is not available, or if the cable modem is

unable to obtain an IP address or respond to SNMP messages.

Clear Cable Modem Counters

reset

Remove the cable modem with a specific IP address from the station maintenance list and reset it.

Remove all cable modems from the station maintenance list and reset them.

To clear the counters for a cable modem (or for all cable modems) in the station maintenance list, use one of the following commands in cable interface configuration mode.

Table 4-10 Instructions to Clear Cable Modem Counters

Command Purpose

CMTS01(config-if)# clear cable modem

mac-addr

counters

Clear the counters in the station maintenance list for the cable modem with a specific MAC address.

CMTS01(config-if)# clear cable modem

ip-addr

counters

Clear the counters in the station maintenance list for the cable modem with a specific IP address.

CMTS01(config-if)# clear cable modem all counters

Clear the counters in the station maintenance list for all cable modems.

Cisco uBR7200 Series Universal Broadband Router Software Configuration Guide

78-5897-01

4-9

Managing Cable Modems on the HFC Network

Verify Clear Cable Modem Counters

To verify whether or not the counters in the Station Maintenance List are cleared, enter the following command. The station maintenance list counter will be 0.

Configure Traffic Shaping

Configure Downstream Rate Limiting and Shaping

To configure downstreamrate limiting or shape downstream traffic,usethefollowingcommand in cable interface configuration mode.

Table 4-11 Instructions to Conﬁgure Downstream Shaping

Command Purpose

CMTS01(config-if)#

token-bucket

[no]

[shaping]

cable downstream rate-limit weighted-discard

[expwt <n>]

Enables or disables rate limiting and traffic shaping on the downstream of a cable interface.

Chapter 4 Troubleshooting the System

Note Using Cisco IOS Release 12.0(5)T1 or higher, the software adds downstream calendar

queuing routines and grant shaping application of the calendar queues.

Key command usage is elaborated below:

• To enable rate limiting on the given downstream port using the token bucket policing algorithm,

issue the cable downstream rate-limit token-bucket command.

• To enable rate limiting on the given downstream port using the token bucket policing algorithm

with traffic shaping, issue the cable downstream rate-limit token-bucket shaping command.

• To enable rate limiting on the given downstream port using the token bucket policing algorithm

with a specifictraffic shaping timegranularity, issue the cabledownstream rate-limit token-bucket shaping granularity 8 command. Acceptable values are 1, 2, 4, 8, or 16 msecs.

• To enable rate limiting on the given downstream port using the token bucket policing algorithm

with a specific maximum traffic shaping buffering delay, issue the cable downstream rate-limit token-bucket shaping granularity 8 command. Acceptable values are 128, 256, 512, or

1028 msecs.

• To remove rate limiting on the given downstream port, issue the cable downstream rate-limit

token-bucket command.

• To enable rate limiting on the given downstream port using a weighted packet discard policing

algorithm and to assign a weight for the exponential moving average of loss rate value, issue the

cable downstream rate-limit weighted-discard 3 command. Acceptable values are 1 to 4.

Configure Upstream Rate Limiting and Shaping

You can rate limit and shape traffic on a DOCSIS upstream channel. This delays the scheduling of the upstream packet, which in turn causes the packet to be buffered on the cable CPE device, instead of being dropped. This allows the user’s TCP/IP stack to pace the application traffic appropriately and approach throughput commensurate with the subscriber’s defined QoS levels.

Cisco uBR7200 Series Universal Broadband Router Software Configuration Guide

4-10

78-5897-01

Chapter 4 Troubleshooting the System

To configure this, use the following command in cable interface configuration mode.

Table 4-12 Instructions to Conﬁgure Upstream Shaping

Command Purpose

CMTS01(config-if)#

[token-bucket]

[no]

cable upstream

<n1>

rate-limit

Enables or disables DOCSIS rate limiting or shaping on an upstream channel. <n1> depends on the number of upstream channels on the specific cable modem card.

Using Cisco IOS Release 12.0(5)T1 or higher, the software supports:

• Generic calendar queuing routines

• New token bucket policing function

• Grant shaping application of the calendar queues

• Upstream rate shaping option to the token-bucket keyword

• A default state change from 1 second burst policing to token-bucket with shaping

Managing Cable Modems on the HFC Network

Tips Upstream grant shaping is per CM (SID). Shaping can be enabled or disabled for the

token-bucket algorithm.

Note Before the introduction of this feature, the CMTS would drop bandwidth requests from a

CM it detected as exceeding its configured peak upstream rate. Such request dropping affects the throughput performance of IP-based protocols such as FTP, TCP, and SMTP. With this feature, the CMTS can shape (buffer) the grants for a CM that is exceeding its upstream rate, rather than dropping the bandwidth requests.

CMTS01# show interface c3/0 sid 1 counters Sid Inpackets Inoctets Outpackets Outoctets Ratelimit Ratelimit BWReqDrop DSPktDrop 1 67859 99158800 67570 98734862 2579 0

Configure Spectrum Management (without the Cisco MC16S Cable Modem Card)

Blind Strategies and Time Scheduled Combined

The Cisco uBR7200 series software supports combined blind and time scheduled spectrum management using Cisco IOS Release 12.0(5)T1 images or higher:

• Using blind spectrum management, the number of lost station management messages exceeding a

configured threshold (default = 10) initiates an upstream channel frequency reassignment. The Cisco uBR7200 series moves all cable modems on the upstream port by sending UCD messages that contain the next frequency and input power level defined in the spectrum management group. The frequency change occurs rapidly without data loss and minimal latency.

78-5897-01

Cisco uBR7200 Series Universal Broadband Router Software Configuration Guide

4-11

Managing Cable Modems on the HFC Network

• Using time scheduled spectrum management, the upstream channel frequency reassignment

process is initiated at a configured time of day or week.

With combined blind and time scheduled strategies, blind hop tables are given time-variant configurability. The frequency or subband list can change with time. Blind frequency hop is performed within the spectrum specified to be currently available. An example follows:

uBR(config)# cable spectrum-group 2 time Mon 09:00:00 frequency 10000000 uBR(config)# cable spectrum-group 2 time Tue 09:05:00 delete frequency 10000000 uBR(config)# cable spectrum-group 2 time Tue 09:00:00 frequency 5000000 uBR(config)# cable spectrum-group 4 time Fri 09:00:00 band 15000000 25000000 uBR(config)# cable spectrum-group 4 time Sat 09:00:00 delete band 15000000 25000000

Guided Frequency Hop

Using guided frequency hop, the upstream channel frequency is reassigned if a threshold number or percentage of cable modems suddenly go offline. You can adjust the thresholds and assign explicit frequencies or frequency subbands and associated input power levels in the unified spectrum group table. The Cisco uBR7200 series locates the defined channel or a suitable channel and moves all cable modems on the upstream port.

The example below shows the Cisco uBR7200 series’ ability to force the CTMS to change the upstream to another frequency before the CMTS sends a message to increase output power levels. You can configure the frequency hop table so that the next entry has the same frequency, but a different power level:

uBR(config)# cable spectrum-group 2 frequency 20000000 uBR(config)# cable spectrum-group 2 frequency 20000000 2 uBR(config)# cable spectrum-group 2 frequency 20000000 -2 uBR(config)# cable spectrum-group 2 frequency 22000000 uBR(config)# cable spectrum-group 2 frequency 22000000 2 uBR(config)# cable spectrum-group 2 frequency 22000000 3

Chapter 4 Troubleshooting the System

The order of the configuration commands defines the order which frequency or power level is changed. There is always a single allocation set per-spectrum group, listing the currently available bands. In the case of a shared spectrum group, there is also a single free set and “in-use” set since there is a single RF domain. Otherwise, there are free and in-use sets for each upstream port since each upstream port has its own RF domain.

4-12

Cisco uBR7200 Series Universal Broadband Router Software Configuration Guide

78-5897-01

Chapter 4 Troubleshooting the System

Sample output:

noisy1#show cable spec Group Frequency Upstream Weekly Scheduled Power Shared No. Band Port Availability Level Spectrum (Mhz) From Time: To Time: (dBmV)

1 10.000- 0.000 1 No 1 11.000- 0.000 1 No 1 12.000- 0.000 1 No 1 13.000- 0.000 1 No 1 14.000- 0.000 1 No 2 10.000-15.000 2 No 2 10.208 [0.40] Cable3/0 U1 2 3 20.000- 0.000 3 Yes 3 21.000- 0.000 3 Yes 3 22.000- 0.000 3 Yes 3 23.000- 0.000 3 Yes 3 24.000- 0.000 3 Yes 3 0.400 [0.80] Cable3/0 U2 3 4 20.000-25.000 4 Yes 4 20.800 [1.60] Cable3/0 U3 4 5 10.000- 0.000 5 No 5 11.000- 0.000 5 No 5 12.000- 0.000 5 No 5 13.000- 0.000 Mon 17:06:00 --- --:--:-- 5 No 5 14.000- 0.000 Mon 17:08:00 --- --:--:-- 5 No 5 13.000- 0.000 Mon 17:10:00 --- --:--:-- 5 No 5 1.600 [3.20] Cable3/0 U4 5 6 10.000-13.000 6 No 6 13.000-15.000 Mon 17:11:00 Mon 17:12:00 6 No 6 10.800 [1.60] Cable3/0 U5 0

Managing Cable Modems on the HFC Network

To display information about a specific interface or upstream port, enter the following command:show cable hop cable-if [upstream portnum]. Information lines describe the frequency hop status of an

upstream port.

Table 4-13 Show Cable Hop Parameter Descriptions

Field Description

Upstream Port The upstream port for this information line Port Status Show “down” if frequency is unassigned, “admindown” if the port is

shutdown, or the center frequency of the channel if the port is up Poll Rate The rate station maintenance polls are generated (msec) Missed Poll Count The number of missing polls Min Poll Sample The number of polls in the sample Missed Poll Pcnt The ratio of missing polls to the number of polls displayed as a percentage Hop Thres Pcnt The level that the missed poll percentage must exceed to trigger a frequency

hop expressed as a percentage Hop Period The maximum rate which frequency hopping will occur (seconds) Corr FEC Errors The number of correctable FEC errors on this upstream port Uncorr FEC Errors The number of uncorrectable FEC errors on this upstream port

78-5897-01

Cisco uBR7200 Series Universal Broadband Router Software Configuration Guide

4-13

Managing Cable Modems on the HFC Network

Sample output:

noisy1#show cable hop Upstream Port Poll Missed Min Missed Hop Hop Corr Uncorr Port Status Rate Poll Poll Poll Thres Period FEC FEC (ms) Count Sample Pcnt Pcnt (sec) Errors Errors Cable3/0/U0 down 1000 * * * frequency not set * * * 0 0 Cable3/0/U1 admindown 1000 * * * interface is down * * * 0 0 Cable3/0/U2 admindown 1000 * * * interface is down * * * 0 0 Cable3/0/U3 admindown 1000 * * * interface is down * * * 0 0 Cable3/0/U4 admindown 1000 * * * interface is down * * * 0 0 Cable3/0/U5 admindown 1000 * * * interface is down * * * 0 0 Cable4/0/U0 10.800 Mhz 1000 0 0 ----- 100% 300 0 0 Cable6/0/U0 down 1000 * * * frequency not set * * * 0 0

Spectrum Management Debug and Test Commands

To enable display of frequency hopping debugging messages, enter:

debug cable freqhop

To enable display of spectrum management debugging messages, enter:

debug cable specmgmt

Chapter 4 Troubleshooting the System

This command also enables display of channel width list and offer list for the show cable spectrum-group command.

To force a frequency hop decision on the port or ports, enter:

test cable hop

Show Cable Hop Command

Using Cisco IOS Release 12.0(5)T1 or higher headend images, you can use the following command to obtain specific upstream interface information:

show cable hop

cable-if[upstream portnum

cable-if

[upstream <

portnum

]

4-14

Cisco uBR7200 Series Universal Broadband Router Software Configuration Guide

78-5897-01

Chapter 4 Troubleshooting the System

Table 4-14 Show Cable Hop Parameter Descriptions

Field Description

Upstream Port The upstream port for this information line Port Status Show “down” if frequency is unassigned, “admindown” if the port is

Poll Rate The rate station maintenance polls are generated (msec) Missed Poll Count The number of missing polls Min Poll Sample The number of polls in the sample Missed Poll Pcnt The ratio of missing polls to the number of polls expressed as a percentage Hop Thres Pcnt The level that the missed poll percentage must exceed to trigger a frequency

Hop Period The maximum rate which frequency hopping will occur (seconds) Corr FEC Errors The number of correctable FEC errors on this upstream port Uncorr FEC Errors The number of uncorrectable FEC errors on this upstream port

Managing Cable Modems on the HFC Network

shutdown, or the center frequency of the channel if the port is up

hop expressed as a percentage

Using Cisco IOS Release 12.0(5)T1 or higher headend images, you can use the following command to obtain specific upstream interface information:

show cable hop

Table 4-15 Upstream Port Parameter Descriptions

cable-if

[upstream <

portnum

Field Description

Upstream Port The upstream port for this information line Port Status Show “down” if frequency is unassigned, “admindown” if the port is

shutdown, or the center frequency of the channel if the port is up Poll Rate The rate station maintenance polls are generated (msec) Missed Poll Count The number of missing polls Min Poll Sample The number of polls in the sample Missed Poll Pcnt The ratio of missing polls to the number of polls expressed as a percentage Hop Thres Pcnt The level that the missed poll percentage must exceed to trigger a frequency

hop expressed as a percentage Hop Period The maximum rate at which frequency hopping will occur (seconds)

78-5897-01

Cisco uBR7200 Series Universal Broadband Router Software Configuration Guide

4-15

Polling Cable Modems

Chapter 4 Troubleshooting the System

Table 4-15 Upstream Port Parameter Descriptions (continued)

Field Description

Corr FEC Errors The number of correctable FEC errors on this upstream port Uncorr FEC Errors The number of uncorrectable FEC errors on this upstream port

Sample output:

Debug and Test Commands

To enable display of frequency hopping debugging messages, enter:

debug cable freqhop

To enable display of spectrum management debugging messages, enter:

debug cable specmgmt

To force a frequency hop decision on the port or ports, enter:

test cable hop

cable-if Iportnum

Polling Cable Modems

Cisco IOS Release 12.0(7)XR2, Cisco IOS Release 12.1(1a)T1 or higher CMTS images, contain modem status enhancements. You can obtain operating statistics and determine the state of cable modems on the network.

The Cisco uBR7200 series supports polling ofcable modems to obtain parameter and statusinformation on an ongoing basis. Two new Cisco IOS commands are added to support the feature:

• The cable modem remote command configures the router for the polling interval; the no version

of this command disables the status polling.

• The show cable modem remote-query command displays the collected information: downstream

receivepower level,downstream signal to noise ratio, upstream power level, micro reflection in dB.

The Cisco uBR7200 series polls cable modems on the network and caches the state information on the CMTS, allowing administrators to use SNMP to manage the system.

This section describes how you can enable this. See the following configuration tasks:

• Enable SNMP (required)

• Configure Remote Modem Monitoring (required)

4-16

Cisco uBR7200 Series Universal Broadband Router Software Configuration Guide

78-5897-01

Chapter 4 Troubleshooting the System

Enable SNMP

Command Purpose

Router(config)# snmp-server manager

Router(config)# snmp-server community [ [

Permissions

]

Community String

]

Opens the SNMP manager Deﬁnes user permissions

Configure Remote Modem Monitoring

Command Purpose

Router(config)# cable modem remote-query [Community string]

[polling interval]

Speciﬁes how often SNMP polls the modem and allows you to conﬁgure access

Verifying Remote Query Information

To display information from a queried modem, enter the show cable modem remote-query command.

R7732-01-uBR7246#sh cable modem remote-query IP address MAC address S/N US DS Tx Time Micro (dB) Modem Ratio Power Power Offset Reflection State

5.108.1.2 0010.4bd7.ccf2 0.0 0.0 0.0 0 0 offline

5.109.1.2 0000.0000.0022 0.0 0.0 0.0 0 0 offline

5.110.1.2 0000.0000.0023 0.0 0.0 0.0 0 0 offline

5.108.1.5 0000.0000.0026 0.0 0.0 0.0 0 0 offline

5.108.1.4 0000.0000.0024 0.0 0.0 0.0 0 0 offline

5.108.1.3 0000.0000.0025 0.0 0.0 0.0 0 0 offline

Polling Cable Modems

Tips To display debugging information, enter the debug cable remote-query command.

See the following for an example debug message of a successful poll of a cable modem:

router# debug cable remote-query remote-query debugging is on . For IP address 209.165.200.223 Nov 10 15:56:50.241: docsIfSignalQualityEntry.5.4 = 380 Nov 10 15:56:50.241: docsIfMibObjects.2.2.1.3.2 = 360 Nov 10 15:56:50.245: docsIfDownstreamChannelEntry.6.4 = -30 Nov 10 15:56:50.245: docsIfUpstreamChannelEntry.6.3 = 12422 Nov 10 15:56:50.249: docsIfSignalQualityEntry.6.4 = 0 Nov 10 15:56:50.477:

See the following for an example debug message when the waiting queue at the CMTS is empty:

SNMP proxy exec got event, but queue is empty

See the following for an example debug message when you try to modify the polling interval or community string while polling in is progress:

Community string if modified will not be reflected

Note The polling interval will be changed. To change the community string, you must

unconfigure the snmp-server community command and reconfigure it with the new community string.

78-5897-01

Cisco uBR7200 Series Universal Broadband Router Software Configuration Guide

4-17

Understanding Show Command Responses

Monitoring and Maintaining Remote Querying

Use the following show commands to gather status information about the specified modems.

Command Purpose

Router# show cable flap-list

Router# show cable modem

Router# show cable modem remote-query

Router# show interface cable

Router# show interface cable sid

Displays statistics on the quality of the modem connection.

Displays statistics on modem states. Displays statistics gathered by SNMP agents on

modem states. Displays statistics on the quality of the cable

interface. Displays statistics on the service IDs of the speciﬁed

modems.

Chapter 4 Troubleshooting the System

Understanding Show Command Responses

General Show Commands

Key show commands include:

• show cable modem

• show interface cable

• show cable qos profile

• show cable modulation profile

• show cable spectrum-group

Additional or changed show commands using Cisco IOS Release 12.0(7)XR2, Cisco IOS Release 12.1(1a)T1, or higher CMTS images include the following:

• The show cable qos command shows cable qos-profile n command, where the optional argument

n can be used to display a specific profile.

• The show int cx/y sid command displays more complete Service ID (SID) status information.

• The show cable modem command displays a list of options for a single modem to be specified by

entering either the RF CPE device's IP address or MAC address: SNR information for each cable modem on each interface, summary display of the total number of modems connected for each upstream channel, total number of registered and unregistered modems for the specified interface or upstream, total number of offline modems for the specified interface or upstream and status for each offline modem before it went offline.

• The show cable burst-profile command has been removed. Its functions have been incorporated

into the show cable modulation-profile command, which now includes an added option number that displays the modulation profile number.

4-18

Cisco uBR7200 Series Universal Broadband Router Software Configuration Guide

78-5897-01

Chapter 4 Troubleshooting the System

• The show cable flap-list and show cable modem commands now indicate when the Cisco

uBR7200 series router has detected an unstable return path for a particular modem and has compensated with a power adjustment. An asterisk appears in the power adjustment field for a modem when a power adjustment has been made; an exclamation point appears when the modem has reached its maximum power transmit level and cannot increase its power level any further.

• The show controller upstream command is enhanced to display the following information on

cable interfaces:

–

Upstream channel utilization in minislots

–

Contention slots

–

Initial ranging slots

–

Minislots lost due to the MAP interrupt being too late.

You can also limit your search for modem status to specific cable interfaces.

Show Cable Modem

Using Cisco IOS Release 12.0(7)XR2, Cisco IOS Release 12.1(1a)T1 or higher, the show cable modem command includes all DOCSIS states, as well as other useful troubleshooting information such as last received upstream RF power level and maximum number of provisioned customer premises equipment.

Understanding Show Command Responses

Note DOCSIS cable modems are required to pass through successive states during registration

and provisioning. Using this information, you can isolate why a cable modem is offline or unavailable.

Specific added information includes the downstream receive power ratio, downstream SNR, upstream and downstream power levels, transmit timing offset, and micro reflections in decibels.

For each upstream channel, you can obtain the following information:

• The total number of modems

• The number of active modems

• The number of registered modems

• The number of unregistered modems

• The number of offline modems.

• The time the modem went offline

• The status before the modem went offline

• The receive power before the modem went offline.

78-5897-01

Cisco uBR7200 Series Universal Broadband Router Software Configuration Guide

4-19

Understanding Show Command Responses

See the sample command output below:

router# show cable modem Interface Prim Online Timing Rec QoS CPE IP address MAC address Sid State Offset Power Cable3/0/U0 1 online 2257 0.00 3 0 10.30.128.142 0090.8330.0217 Cable3/0/U0 2 online 2262 *-0.50 3 0 10.30.128.145 0090.8330.020f Cable3/0/U0 3 online 2260 0.25 3 0 10.30.128.146 0090.8330.0211 Cable3/0/U0 4 online 2256 *0.75 3 0 10.30.128.143 0090.8330.0216 Cable3/0/U0 5 online 2265 *0.50 3 0 10.30.128.140 0090.8330.0214 Cable3/0/U0 6 online 2256 0.00 3 0 10.30.128.141 0090.8330.0215 Cable3/0/U0 7 online 4138 !-1.00 3 1 10.30.128.182 0050.7366.124d Cable3/0/U0 8 online 4142 !-3.25 3 1 10.30.128.164 0050.7366.1245 Cable3/0/U0 9 online 4141 !-3.00 3 1 10.30.128.185 0050.7366.17e3 Cable3/0/U0 10 online 4142 !-2.75 3 0 10.30.128.181 0050.7366.17ab Cable3/0/U0 11 online 4142 !-3.25 3 1 10.30.128.169 0050.7366.17ef

The show cable modem indicates when the Cisco uBR7200 series router has detected an unstable return path for a particular CM and has compensated with a power adjustment. An asterisk appears in the power adjustment field for a CM when a power adjustment has been made; an exclamation point appears when the CM has reached its maximum power transmit level and cannot increase itspowerlevel any further.

Columns are described below:

• The prim Sid column reveals the primary (lifeline) service identifierassigned to the cable modem.

• The SID column is the service identifier.

• The Online State column reveals the state of the modem; values include:

–

offline—Cable modem considered offline

–

offline time—the time the cablemodem went offline;theformatisthesameas other show cable modem commands (month, day, time, and year)

–

init (r1)—Cable modem sent initial ranging

–

init (r2)—Cable modem is ranging

–

init (rc)—Cable modem ranging complete

–

init (d)—Dhcp request received

–

init (i)—Dhcp reply received; IP address assigned

–

init (o)—Option file transfer started

–

init (t)—TOD exchange started

–

online—Cable modem registered, enabled for data

–

online(d)—Cable modem registered, but network access for the cable modem is disabled

–

online(pk)—Cable modem registered, BPI enabled and KEK assigned

–

online(pt)—Cable modem registered, BPI enabled and TEK assigned

–

reject (m)—Cable modem did attempt to register; registration was refused due to bad MIC

–

reject (c)—Cable modem did attempt to register; registration was refused due to bad COS

–

reject (pk)—KEK modem key assignment rejected

–

reject (pt)—TEK modem key assignment rejected

• The Rec Power column contains the nominal receive power in decibels for this SID

Chapter 4 Troubleshooting the System

4-20

Cisco uBR7200 Series Universal Broadband Router Software Configuration Guide

78-5897-01

Chapter 4 Troubleshooting the System

Note * means the noise power adjustment method is activefor this modem; ! means

• The QoS column contains the service class assigned to the modem

• The CPE column identifies the number of devices behind the modem

• The Max CPE column identifies the maximum number of devices configured for the modem

• The IP address reveals the modem’s IP address

• The MAC address reveals the modem’s MAC address

• The Concatenation column reveals if concatenation is enabled (yes) or disabled (no)

• The Rx SNR column reveals the SNR ratio level in dBmV as perceived by the cable modem

Note This parameter is only meaningful for cable modems. A CMTS will return a

• The S/N Ratio column provides values for remote-queried modems.

• The US Power column reveals the transmit power level for the upstream channel in dBmV.

• The DS Power column reveals the received power level at the downstream modem in dBmV.

Understanding Show Command Responses

the modem has reached its maximum transmit power

zero.

Note If the power level measurement is not supported, set this parameter to zero.

Also, if the interface is down, this value will be the CMTS-configured value, the most current CM value, or zero.

• The Tx Timing Offset shows the current round triptime at the CM. The valueis used to synchronize

upstream transmission to the CMTS and is measured in units of 6.25 microseconds.

• The Micro (dB) Reflection column is the total microreflections including in-channel response as

perceived on this interface, measured in Dbc below the signal level.

Note The value is not assumed to return an absolutely accurate value, but gives a

rough indication of microreflections received on this interface.

• The Offline Time column reveals when a modem went offline.

• The Previous State column reveals the modem’s status prior to going offline. See the modem

ranging states given earlier.

• The Rx Power column reveals the last receive power measurement for a modem that is offline

before it went offline.

• SM Exhaust Count reveals the number of times the CMTSdeclared that modem offline.Themodem

can be marked offline for various reasons. Refer to Show Cable Modem Maintenance, page 4-23.

78-5897-01

Cisco uBR7200 Series Universal Broadband Router Software Configuration Guide

4-21

Understanding Show Command Responses

See the following sample for detailed output of the show cable modem command:

router#show cable modem detail Interface SID MAC address Max CPE Concatenation Rx SNR Cable3/0/U0 1 0090.8330.0215 3 yes Cable3/0/U0 2 0090.8330.0213 3 yes Cable3/0/U0 3 0090.8330.0214 3 yes Cable3/0/U0 4 0090.8330.0217 3 yes Cable3/0/U0 5 0090.8330.020f 3 yes Cable3/0/U0 6 0050.7366.17e3 3 no Cable3/0/U0 7 0090.8330.0211 3 yes Cable3/0/U0 8 0050.7366.17af 3 no Cable3/0/U0 9 0090.8330.0216 3 yes Cable3/0/U0 10 0050.7366.1801 3 no Cable3/0/U0 11 0050.7366.124d 3 no Cable3/0/U0 12 0050.7366.1241 3 no Cable3/0/U0 13 0050.7366.17db 3 no Cable3/0/U0 14 0050.7366.1239 3 no Cable3/0/U0 15 0050.7366.17ab 3 no Cable4/0/U0 1 0050.7366.1db1 3 no 26.50 Cable4/0/U1 2 0050.7318.e97f 3 no 23.87 Cable4/0/U1 3 0050.7318.e965 3 no 23.85 Cable4/0/U0 4 0050.7318.e931 3 no 26.72 Cable4/0/U1 5 0050.7318.e92d 3 no 23.31 Cable4/0/U1 6 0050.7318.e97b 3 no 23.85 Cable4/0/U0 7 0050.7366.1d8d 3 no 26.88 Cable4/0/U0 8 0050.7318.e953 3 no 26.54 Cable4/0/U1 9 0050.7366.1d9d 3 no 23.72 Cable4/0/U1 10 0050.7318.e96b 3 no 23.79 Cable4/0/U1 11 0050.7366.1d95 3 no 23.82 Cable4/0/U0 12 0050.7318.e93f 3 no 26.26 Cable4/0/U1 13 0050.7318.e96d 3 no 23.51 Cable4/0/U0 14 0050.7318.e941 3 no 26.69 Cable4/0/U0 15 0050.7366.1dcd 3 no 26.94 Cable4/0/U1 16 0050.7318.e939 3 no 23.98 Cable4/0/U0 17 0050.7366.1d8f 3 no 27.13 Cable4/0/U0 18 0050.7302.3da3 3 no 26.58 Cable4/0/U0 19 0050.7318.e93b 3 no 26.49 Cable4/0/U0 20 0050.7318.e901 3 no 26.68 Cable4/0/U1 21 0050.7366.1dbb 3 no 23.45 Cable4/0/U0 22 0050.7318.e957 3 no 26.35 Cable4/0/U0 23 0050.7318.e985 3 no 26.40 Cable4/0/U0 24 0050.7366.1dbd 3 no 26.69

Chapter 4 Troubleshooting the System

4-22

See the followingsample output of modems connected on upstream channel 0 for cable interface slot 3, port 0:

router#show cable modem cable 3/0 upstream 0 Interface Prim Online Timing Rec QoS CPE IP address MAC address Sid State Offset Power Cable3/0/U0 1 offline 2264 -0.50 2 0 209.165.200.2 0090.8330.0214 Cable3/0/U0 2 offline 4137 !-3.50 2 0 209.165.200.9 0050.7366.17d3 Cable3/0/U0 3 init(d) 4136 !-2.50 2 0 209.165.200.0 0050.7366.17ab Cable3/0/U0 4 init(d) 4138 !-4.75 2 0 209.165.200.0 0050.7366.1803 Cable3/0/U0 5 init(d) 4137 !-2.25 2 0 209.165.200.0 0050.7366.1801 Cable3/0/U0 6 init(o) 2251 -0.25 2 0 209.165.200.3 0090.8330.0213 Cable3/0/U0 7 offline 2264 0.75 2 0 209.165.200.4 0090.8330.020f Cable3/0/U0 8 offline 2266 -0.50 2 0 209.165.200.5 0090.8330.0211 Cable3/0/U0 9 init(rc) 4662 1.00 2 0 209.165.200.0 00d0.bad3.c459

Cisco uBR7200 Series Universal Broadband Router Software Configuration Guide

78-5897-01

Chapter 4 Troubleshooting the System

See the following sample output of unregistered modems connected on upstream channel 0 for cable interface 3, port 0:

router#show cable modem cable 3/0 upstream 0 unregistered Interface Prim Online Timing Rec QoS CPE IP address MAC address Sid State Offset Power Cable3/0/U0 1 offline 2264 -0.50 2 0 209.165.200.2 0090.8330.0214 Cable3/0/U0 2 offline 4137 !-3.50 2 0 209.165.200.9 0050.7366.17d3 Cable3/0/U0 3 init(d) 4136 !-2.75 2 0 209.165.200.0 0050.7366.17ab Cable3/0/U0 4 init(d) 4137 !-3.25 2 0 209.165.200.0 0050.7366.1803 Cable3/0/U0 5 init(d) 4141 !-2.75 2 0 209.165.200.0 0050.7366.1801 Cable3/0/U0 6 offline 2251 -0.25 2 0 209.165.200.3 0090.8330.0213 Cable3/0/U0 7 offline 2254 -1.00 2 0 209.165.200.4 0090.8330.020f Cable3/0/U0 8 offline 2248 0.00 2 0 209.165.200.5 0090.8330.0211 Cable3/0/U0 9 init(rc) 4665 -0.50 2 0 209.165.200.0 00d0.bad3.c459

See the following sample output of offline modems connected on upstream channel 0 for cable interface 3, port 0:

router#show cable modem cable 3/0 upstream 0 offline Interface MAC address Prim Previous Offline Rx Rx SM Sid State Time Power SNR Exhaust Count Cable3/0/U0 0050.7366.17d3 2 init(o) Jan 16 20:30:26 !-3.50 ----- 1 Cable3/0/U0 0090.8330.0213 6 init(o) Jan 16 20:30:55 -0.25 ----- 181 Cable3/0/U0 0090.8330.020f 7 init(o) Jan 16 20:31:07 -1.00 ----- 181 Cable3/0/U0 0090.8330.0211 8 init(o) Jan 16 20:31:23 0.00 ----- 181

Understanding Show Command Responses

Show Cable Modem Maintenance

When a cable modem is detected to be offline by the CMTS—no reply after 16 retries of station maintenance requests—the cable modem is marked offline.Besides marking the cable modem and SID state offline, the SID is removed immediately from the CMTS ranging list and an aging timer is started to cleanup the SID completely if the cable modem does not attempt to come online within the next 24 hours.

Output fields are described below:

• The "SM Exhausted Count" value refers to the number of times a cable modem was dropped

because it did not reply to station maintenance requests. A CM is removed from the station maintenance list after 16 times of periodic ranging opportunity without seeing the RNG_REQ from the modem.

• The "SM Aborted Count" value refers to the number of times the CM was dropped because its

operational parameters were unacceptable. This includes such reasons as the power levelis outside the acceptable range, or the timing offset keeps changing. The respective times in the command output indicate when this happened.

78-5897-01

Cisco uBR7200 Series Universal Broadband Router Software Configuration Guide

4-23

Understanding Show Command Responses

Following is a response to the show cable modem maintenance command using Cisco IOS Release 12.0(5)T1:

uBR7200#show cable modem maintenance

Interface SID MAC Address SM Exhausted SM Aborted Count Time Count Time Cable4/0/U1 1 0010.7b6b.5e27 4 Apr 29 19:33:19 0 Cable4/0/U0 2 0010.7b6b.5e15 8 Apr 29 19:34:55 0 Cable4/0/U2 11 0050.731c.b025 1 Apr 29 16:43:39 0 Cable4/0/U0 13 0050.731c.b021 1 Apr 29 15:58:43 0 Cable4/0/U0 16 0050.731c.b009 1 Apr 29 15:58:28 0 Cable4/0/U0 20 0050.731c.bfed 1 Apr 28 14:36:22 0 Cable4/0/U2 24 0050.731c.b023 1 Apr 27 10:30:36 0 Cable4/0/U1 27 0050.731c.bfeb 1 Apr 28 14:54:53 0 Cable4/0/U2 28 0050.731c.bfdf 1 Apr 28 14:50:55 0 Cable4/0/U1 30 0050.7366.1a71 2 Apr 29 17:49:00 0 Cable4/0/U1 31 0050.7366.1bab 3 Apr 29 16:21:47 0 Cable4/0/U1 32 0050.731c.bfe7 0 2 Jan 1 09:00:00 Cable4/0/U1 33 0050.731c.bfd3 4 Apr 29 15:09:28 0 Cable4/0/U2 35 0050.731c.b041 1 Apr 29 16:17:41 0 Cable4/0/U1 36 0050.7366.1ab9 2 Apr 29 16:53:26 0

Chapter 4 Troubleshooting the System

Show Interface Cable

To display cable interface information, use the show interface cable privileged EXEC command: show interface cable slot/port [downstream | upstream].

See the following sample show interface cable command output for a cable modem located in slot 6/port 0 using the earlier Cisco IOS Release 12.1(5)T1 software:

router# show interface cable 6/0 Cable6/0 is up, line protocol is up Hardware is BCM3210 FPGA, address is 00e0.1e5f.7a60 (bia 00e0.1e5f.7a60) Internet address is 1.1.1.3/24 MTU 1500 bytes, BW 27000 Kbit, DLY 1000 usec, rely 255/255, load 1/255 Encapsulation, loopback not set, keepalive not set ARP type: ARPA, ARP Timeout 04:00:00 Last input 4d07h, output 00:00:00, output hang never Last clearing of “show interface” counters never Queueing strategy: fifo Output queue 0/40, 0 drops; input queue 0/75, 0 drops 5 minute input rate 0 bits/sec, 0 packets/sec 5 minute output rate 0 bits/sec, 0 packets/sec 10908 packets input, 855000 bytes, 0 no buffer Received 3699 broadcasts, 0 runts, 0 giants, 0 throttles 3 input errors, 3 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort 5412 packets output, 646488 bytes, 0 underruns 0 output errors, 0 collisions, 13082 interface resets 0 output buffer failures, 0 output buffers swapped out

Note For more recent images such as Cisco IOS Release 12.1(1a)T1 or higher, the show

interface upstream command is enhanced to display details on the MAC scheduler state

for an upstream port. Refer to “Enhanced Show Interface Upstream Output” section on page 4-30.

4-24

Cisco uBR7200 Series Universal Broadband Router Software Configuration Guide

78-5897-01

Chapter 4 Troubleshooting the System

Table 4-16 Show Interface Cable Command Field Descriptions

Field Description

Understanding Show Command Responses

Cable slot/port is up/...administratively down

line protocol is up/...administratively down

Indicates whether the interface hardware is currently active or taken down by the administrator

Indicates whether the software processes that handle the line protocol believe the interface is usable or if it has been

taken down by the administrator hardware Hardware type and address Internet address Internet address followed by subnet mask MTU Maximum Transmission Unit (MTU) of the interface BW Bandwidth of the interface in kilobits per second DLY Delay of the interface in microseconds rely Reliability of the interface as a fraction of 255, calculated

as an exponential average over 5 minutes. (For example,

255/255 is 100% reliability) load Load on the interface as a fraction of 255, calculated as an

exponential average over 5 minutes. (For example,

255/255 is complete saturation.) Encapsulation Encapsulation method assigned to this interface. ARP type Type of Address Resolution Protocol (ARP) and timeout

value assigned Last input Number of hours, minutes, and seconds since the last

packet was successfully received by an interface output Number of hours, minutes, and seconds since the last

packet was successfully transmitted by an interface Last clearing of “show

interface” counters

Timewhenthe counters that measure cumulative statistics,

such as number of bytes transmitted and received, were

last reset to zero Queueing strategy Displays the type of queueing configured for this interface.

In the example output, the type of queueing configured is

First In First Out (FIFO) Output queue Number of packets in the output queue. The format of this

number is A/B where A indicates the number of packets in

the queue, and B indicates the maximum number of

packets allowed in the queue drops Indicates the number of packets dropped due to a full

queue input queue/drops Number of packets in the input queue. The format of this

number is A/B where A indicates the number of packets in

the queue, and B indicates the maximum number of

packets allowed in the queue.

78-5897-01

Cisco uBR7200 Series Universal Broadband Router Software Configuration Guide

4-25

Understanding Show Command Responses

Table 4-16 Show Interface Cable Command Field Descriptions (continued)

Field Description

drops Indicates the number of packets dropped due to a full

Chapter 4 Troubleshooting the System

queue

Five minute input rate Five minute output rate

Average number of bits andpackets transmitted per second

in the last five minutes packets input Total number of error-free packets received by the system bytes input Total number of bytes, including data and MAC

encapsulation, in the error-free packets received by the

system no buffer Number of received packets discarded because there was

no buffer space in the main system Received broadcast Totalnumberofbroadcastor multicast packets received by

the interface runts Number of packets that are discarded because they are

smaller than the medium’s minimum packet size giants Number of packets that are discarded because they exceed

the medium’s maximum packet size input errors Includes runts, giants, no buffers, CRC, frame, overrun,

and ignored counts CRC Indicates the number of times the cyclic redundancy

checksum generated by the originating LAN station or

far-end device does not match the checksum calculated

from the data received

4-26

frame Number of packets received incorrectly (with a CRC error

and a non-integer number of octets) overrun Number of times the receiver hardware was unable to

forward received data to a hardware buffer because the

input rate exceeded the receiver’s ability to handle the data ignored Number of received packets ignored by the interface

because the interface hardware ran low on internal buffers packets output Total number of messages transmitted by the system bytes Total number of bytes, including data and MAC

encapsulation, transmitted by the system underruns Number of times the transmitter ran faster than the

receiving device could handle output errors Sum of all errors that prevented the final transmission of

packets out of the interface being examined interface resets Number of times an interface has been completely reset

Cisco uBR7200 Series Universal Broadband Router Software Configuration Guide

78-5897-01

Chapter 4 Troubleshooting the System

Table 4-16 Show Interface Cable Command Field Descriptions (continued)

Field Description

output buffer failures Number of times the output buffer has failed output buffer swapped out Number of times the output buffer has been swapped out

See the following sample output for the downstream cable interface of slot 6 on port 0 from the show interface cable downstream command:

router# show interface cable 6/0 downstream Cable6/0: Downstream is up 111947771 packets output, 1579682655 bytes, 0 discarded 0 output errors

Table 4-17 Show Interface Cable Downstream Command Field Descriptions

Field Description

Cable Indicates the location of the downstream interface. Downstream is up/...administratively down Indicates the administrative state of the interface. packets output Total number of packets transmitted out of this interface. bytes Total number of bytes transmitted out of this interface discarded Total number of packets discarded output errors Sum of all errors that prevented downstream transmission of

Understanding Show Command Responses

packets out of this interface

See the following sample output for the upstream cable interface located in slot 3/port 0 from the show interface cable upstream command:

router# show interface cable 3/0 upstream 0 Cable3/0: Upstream 0 is up Received 16873 broadcasts, 0 multicasts, 73310 unicasts 0 discards, 89053 errors, 0 unknown protocol 90183 packets input, 1 uncorrectable 89042 noise, 0 microreflections Total Modems On This Upstream Channel : 8 (4 active) Default MAC scheduler Queue[Rng Polls] 0/20, fifo queueing, 0 drops Queue[Cont Mslots] 0/104, fifo queueing, 0 drops Queue[CIR Grants] 0/20, fair queueing, 0 drops Queue[BE Grants] 0/30, fair queueing, 0 drops Queue[Grant Shpr] 0/30, calendar queueing, 0 drops Reserved slot table currently has 0 CBR entries Req IEs 134469315, Req/Data IEs 0 Init Mtn IEs 385879, Stn Mtn IEs 131059 Long Grant IEs 10766, Short Grant IEs 15895 Avg upstream channel utilization : 1% Avg percent contention slots : 97% Avg percent initial ranging slots : 0% Avg percent minislots lost on late MAPs : 0% Total channel bw reserved 0 bps CIR admission control not enforced Current minislot count : 6676390 Flag: 0 Scheduled minislot count : 6676545 Flag: 0

Table 4-18 describes the fields shown in the show interface cable upstream display.

78-5897-01

Cisco uBR7200 Series Universal Broadband Router Software Configuration Guide

4-27

Understanding Show Command Responses

Table 4-18 Show Interface Cable Upstream Command Field Descriptions

Field Description

Cable Indicates the location of the upstream interface

Chapter 4 Troubleshooting the System

Upstream is

Indicates the administrative state of the upstream interface up/...administratively down

Received broadcasts Number of broadcast packets received through this

upstream interface multicasts Number of multicast packets received through this

upstream interface unicasts Number of unicast packets received through this interface discards Number of packets discarded by this interface errors Sum of all errors that prevented upstream transmission of

packets through this interface unknown protocol Number of packets received that were generated using a

protocol unknown to the Cisco uBR7246 packets input Number of packets received through this upstream

interface that were free from errors corrected Number of error packets received through this upstream

interface that were corrected uncorrectable Number of error packets received through this upstream

interface that could not be corrected noise Number of upstream packets corrupted by line noise microreflections Number of upstream packets corrupted by

microreflections Guaranteed-rate service queue

depth

Number of bandwidth requests queued up in the

Guarantee-rate queue. This queue is only available to

modems that have a reserved minimum upstream rate in

their Class of Service Best-effort service queue depth Number of bandwidth requests queued up in the

Best-effort queue. This queue is available to all modems

that do not have any reserved rate on the upstream Total Modems On This

Upstream Channel

Number of cable modems currently sharing this upstream

channel. This field also shows how many of these modems

are active Current Total Bandwidth

Reserved

Total amount of bandwidth reserved by all modems

sharing this upstream channel that require bandwidth

reservation. The Class of Service for these modems

specifiessomenon-zerovalue for the guaranteed-upstream

rate. When one of these modems is admitted on the

upstream, this field value is incremented by this

guaranteed-upstream rate value

4-28

Cisco uBR7200 Series Universal Broadband Router Software Configuration Guide

78-5897-01

Chapter 4 Troubleshooting the System

Table 4-18 Show Interface Cable Upstream Command Field Descriptions (continued)

Field Description

Understanding Show Command Responses

CIR admission control (formerly: Current Admission Control Status)

Indicates the status of admission control on the upstream channel

ENFORCED status allows users to enable admission control on a per port basis. This controls how limited bandwidth is allocated. NOTENFORCED status indicates that there is no admission control. Every modem that registers with a class of service specifying a minimum upstream rate will be admitted by the CMTS regardless of how much aggregate bandwidth is actually available.

Users enable admission control by using the admission control CLI

Default MAC scheduler Indicates the status of the MAC scheduler as being in

default mode as opposed to Automated Test Procedure (ATP)

Queue[Rng Polls] TheMACschedulerqueue showing the number of ranging

polls

Queue[Cont Mslos] The MAC scheduler queue showing the number of forced

contention request slots in MAPS

Queue[CIR Grants] The MAC scheduler queue showing the number of CIR

grants pending

Queue[BE Grants] The MAC scheduler queue showing the number of BE

grants pending

Queue[Grant Shpr] The MAC scheduler queue showing the number of grants

that have been buffered for traffic shaping drops Number of packets dropped Reservedslottablecurrentlyhas

0 CBR entries

Number of CBR sessions active on an upstream channel at

any given time Req IEs The running counter of request IEs sent in MAPS Req/Data IEs The counter of request/data IEs sent in MAPS Init Mtn IEs The counter of Initial Maintenance IEs Stn Mtn IEs Number of station maintenance (ranging poll) IEs Long Grant IEs Number of long grant IEs Short Grant IEs Number of short grant IEs Avg upstream channel

utilization

Indicates on average what percent of the upstream channel

bandwidth is being used Avg percent contention slots Indicates on average what percent of slots are in

contention state Avg percent initial ranging slots Indicates on average what percent of slots are in initial

ranging state

78-5897-01

Cisco uBR7200 Series Universal Broadband Router Software Configuration Guide

4-29

Understanding Show Command Responses

Table 4-18 Show Interface Cable Upstream Command Field Descriptions (continued)

Field Description

Chapter 4 Troubleshooting the System

Avg percent minislots lost on late MAPs

Current minislot count (formerly: Last Minislot Stamp (current_time_base))

Scheduled minislot count (formerly: Last Minislot Stamp (scheduler_time_base))

Enhanced Show Interface Upstream Output

The show interface cable upstream command is enhanced in Cisco IOS Release 12.0(7)XR2, Cisco IOS Release 12.1(1a)T1, or higher CMTS images to display detailed MAC scheduler state information for the upstream port. The example below illustrates the new display:

cmts#show interface cable 3/0 upstream 0 Cable3/0:Upstream 0 is up Received 13 broadcasts, 0 multicasts, 110 unicasts 0 discards, 106 errors, 0 unknown protocol 123 packets input, 0 uncorrectable 106 noise, 0 microreflections Total Modems On This Upstream Channel :3 (3 active) Default MAC scheduler Queue[Rng Polls] 0/20, fifo queueing, 0 drops Queue[Cont Mslots] 0/104, fifo queueing, 0 drops Queue[CIR Grants] 0/20, fair queueing, 0 drops Queue[BE Grants] 0/30, fair queueing, 0 drops Queue[Grant Shpr] 0/30, calendar queueing, 0 drops Reserved slot table currently has 2 CBR entries Req IEs 280185, Req/Data IEs 0 Init Mtn IEs 800, Stn Mtn IEs 49 Long Grant IEs 26, Short Grant IEs 15 Avg upstream channel utilization :1% Avg percent contention slots :97% Avg percent initial ranging slots :1% Avg percent minislots lost on late MAPs :0% Total channel bw reserved 192000 bps CIR admission control not enforced Current minislot count :1165412 Flag:1 Scheduled minislot count :1176227 Flag:1

Indicates on averagewhat percent of slots are lost because a MAP interrupt was too late

Indicates the current minislot count at the CMTS. FLAG indicates the timebase reference. This field is used only by developers.

Indicates the furthest minislot count allocated at the indicated time. FLAG indicates the timebase reference. This field is used only by developers.

4-30

New items in the display include:

• Detailed slot queue statistics---Queue [CIR Grants] 0/20, fair queueing, 0 drops in the example

above means that the queue for CIR-service grants has a current depth of 0, a maximum depth of

20. Weighted fair queueing shows grants in this queue.

• CBR slot scheduling table state---The above reserved slot table has 2 CBR entries. This shows that

at the time the command was issued, the MAC scheduler had admitted 2 CBR slots in the reserved slot table.

Cisco uBR7200 Series Universal Broadband Router Software Configuration Guide

78-5897-01

Chapter 4 Troubleshooting the System

• Counters for each type of upstream slot scheduled in the MAPs for this upstream channel---The

“Init Mtn IEs 800” means that the MAC scheduler has added 800 initial maintenance information elements (slots) at the time the show command was issued.

• MAC scheduling statistics to display what percentage of the upstream bandwidth is utilized for

each type of slot on an average.

Show Interface Cable SID

To display per-SID counters for bandwidth requests, use the show interface cable privileged EXEC command: show interface cable interface sid [sid] counters verbose. Data transport over the RF link uses the registered SID address, rather than the Ethernet address. This allows multiple hosts to access the network by using a single cable modem.

Note Cisco IOS Release 12.0(7)XR2 and 12.1(1a)T1 adds the verbose option to provide SID

details.

See the following display output for the verbose keyword extension for SID 1 on interface cable slot 3, port 0:

router# show interface c3/0 sid 1 counters verbose Sid : 1 Input packets : 39 Input octets : 15964 Output packets : 30 Output octets : 8796 BW requests received : 40 Grants issued : 40 Rate exceeded BW request drops : 0 Rate exceeded DS packet drops : 0

Understanding Show Command Responses

78-5897-01

Cisco uBR7200 Series Universal Broadband Router Software Configuration Guide

4-31

Understanding Show Command Responses

See the following display output for the verbose keyword extension for all SIDs on the specified interface:

router# show interface c3/0 sid counters verbose Sid : 1 Input packets : 39 Input octets : 15964 Output packets : 30 Output octets : 8796 BW requests received : 40 Grants issued : 40 Rate exceeded BW request drops : 0 Rate exceeded DS packet drops : 0 Sid : 2 Input packets : 0 Input octets : 0 Output packets : 0 Output octets : 0 BW requests received : 0 Grants issued : 0 Rate exceeded BW request drops : 0 Rate exceeded DS packet drops : 0 Sid : 3 Input packets : 0 Input octets : 0 Output packets : 0 Output octets : 0 BW requests received : 0 Grants issued : 0 Rate exceeded BW request drops : 0 Rate exceeded DS packet drops : 0

Chapter 4 Troubleshooting the System

See the following display for the SIDs connected to the specified interface:

Lab-CMTS# show inter cab 3/0 sid Sid Prim Type Online Admin QoS Create IP Address MAC Address Sid State Status Time 23 stat init(d) enable 2 04:00:54 209.165.200.0 0050.7366.17ab 24 stat init(d) enable 2 04:00:58 209.165.200.0 0050.7366.1803 25 stat init(rc) enable 2 04:01:05 209.165.200.0 00d0.bad3.c459 26 stat init(d) enable 2 04:01:10 209.165.200.0 0050.7366.1801 27 stat offline enable 2 04:01:31 209.165.200.225 0090.8330.0213 28 stat offline enable 2 04:01:59 209.165.200.226 0090.8330.0211 29 stat offline enable 2 04:02:07 209.165.200.227 0090.8330.0214 30 dyn init(o) enable 2 04:03:09 209.165.200.228 0090.833

See the following connection information for all SIDs on the specified interface:

router# show interface c3/0 sid connectivity Sid 1st time Times %online Online time Offline time online Online min avg max min avg max 1 15:37:24 1 99.73 00:00 1h45m 1h45m 00:17 00:17 00:17 2 15:37:24 1 99.73 00:00 1h45m 1h45m 00:17 00:17 00:17 3 15:37:24 1 99.73 00:00 1h45m 1h45m 00:17 00:17 00:17

See the following connection information for SID 1 on the specified interface:

router# show interface c3/0 sid 1 connectivity Sid 1st time Times %online Online time Offline time online Online min avg max min avg max 1 15:37:24 1 99.72 00:00 1h41m 1h41m 00:17 00:17 00:17

4-32

Cisco uBR7200 Series Universal Broadband Router Software Configuration Guide

78-5897-01

Chapter 4 Troubleshooting the System

See the following display for the counters of the SIDs connected to the specified interface:

router# show interface c3/0 sid counters Sid Inpackets Inoctets Outpackets Outoctets Ratelimit Ratelimit BWReqDrop DSPktDrop 1 40 16586 31 9160 0 0 2 0 0 0 0 0 0 3 0 0 0 0 0 0

See the following display for the counters of SID 1 on the specified interface:

router# show interface c3/0 sid 1 counters Sid Inpackets Inoctets Outpackets Outoctets Ratelimit Ratelimit BWReqDrop DSPktDrop 1 39 15964 30 8796 0 0

Table 4-19 describes the fields shown in the output for the show interface cable sid displays.

Table 4-19 show interface cable sid Command Field Descriptions

Field Description

Sid Service identification number

Understanding Show Command Responses

Prim Sid The primary service identifier assigned to the modem Type Indicates this SID was created statically at the timeof registration

or dynamically by the exchange of dynamic service messages between the CM and CMTS

Online State “Online” means the modemowningthis SID is processing traffic.

“Offline” means the modem owning this SID is not processing traffic

Admin Status “Disable”means that the SID has been turned off.“Enable” is the

normal state QoS Quality of service. Create time When the SID was created, number of seconds since the system

booted Input octets (Inoctets) Number of octets received by using this SID Input packets (Inpackets) Number of packets received by using this SID Output octets (Outoctets) Number of octets sent from this SID Output packets

Number of packets sent from this SID (Outpackets)

IP address IP address of the modem owning this SID

78-5897-01

MAC address MAC address of the modem owning this SID BW requests received Number of bandwidth requests received by this SID Grants issued Number of bandwidth requests granted by this SID Rate exceeded BW

Number of bandwidth requests not granted by this SID request drops

Cisco uBR7200 Series Universal Broadband Router Software Configuration Guide

4-33

Troubleshooting Using Cable Flap Lists

Table 4-19 show interface cable sid Command Field Descriptions (continued)

Field Description

Chapter 4 Troubleshooting the System

Rate exceeded DS packet drops

Ratelimit BWReqDrop Number of bandwidth requests not granted by this SID Ratelimit DSPktDrop Number of downstream packets lost by this SID 1st time online Time at which the modem with this SID connected Times online Number of times the modem with this SID has connected % online Percentage of time the modem with this SID has been connected Online time The minimum, average, and maximum number of hours and

Offline time The minimum, average, and maximum number of hours and

Show Cable QoS Profile

Following is a response to the show cable qos profile command. The display shows ToS specifications:

uBR7200#show cable qos profile

Service Prio Max Guarantee Max Max tx TOS TOS Create B class upstream upstream downstream burst mask value by priv > bandwidth bandwidth bandwidth enab 1 0 0 0 0 0 0x0 0x0 cmts(r) no 2 0 64000 0 1000000 0 0x0 0x0 cmts(r) no 3 0 1000 0 1000 0 0x0 0x0 cmts no 4 3 256000 0 512000 0 0x0 0x0 cm no 5 5 1000000 0 10000000 0 0x0 0x0 cm no 6 3 256000 0 512000 0 0x0 0x0 cm yes

Number of downstream packets lost by this SID

minutes the modem with this SID has been connected

minutes the modem with this SID has been disconnected

Note The “r” in the “Create by” column means the first twoclasses of service the CMTS creates

are reserved for CMs that are not online.

Displays upstream packet discards, errors, error-free packets, correctable and uncorrectable errors, noise and microreflection statistics:

show interface slot/downstream-port upstream

Troubleshooting Using Cable Flap Lists

The Cisco uBR7200 series universal broadband routers maintain a database of flapping cable modems to assist in locating cable plant problems. The flapping cable modem detector tracks the upstream and downstream performance of all cable modems on the network, without impacting throughput and performance, or creating additional packet overhead on the broadband network. The cable modem flap

Cisco uBR7200 Series Universal Broadband Router Software Configuration Guide

4-34

78-5897-01

Chapter 4 Troubleshooting the System

list keeps track of the cable modem MAC address, up and down transitions, registration events, missed periodic ranging packets, upstream power adjustments and the physical interface on the Cisco uBR7200 series.

Note Although this is a Cisco proprietary CMTS feature, it is compatible with all

DOCSIS-compliant cable modems. Unlike SNMP, the flap list uses zero bandwidth.

The flap list collects the following station maintenance statistics:

• Detects interface up/down flap; the reinsertion counter counts the number of times a cable modem

comes up and inserts into the network. This helps identify potential problems in the downstream because improperly provisioned cable modems tend to try to reestablish a link repeatedly.

• Detects intermittent upstream; the keepalive hits versus misses is the number of times cable

modems don’t respond or don’t respond to the MAC layer keepalivemessages. If there are a number of misses, this points to a potential problem in the upstream.

• Lists cable modem MAC addresses sorted by flap rate or most recent flap time.

• Shows power adjustment statistics during station maintenance polling; this represents the number

of times the CMTS tells a cable modem to adjust the transmit power more than 3 dB. If constant power adjustments are detected, this usually indicates a problem with an amplifier. By looking at the cable modems in front and behind various amplifiers, you can find the source of failure.

The cable system administrator typically:

• Sets up a script to periodically poll the flap list, for example, every 15 minutes

• Uses the resulting data to perform trend analysis to identify the cable modems that are consistently

in the flap list

• Queries the billing and administrative database for cable modem MAC address-to-street address

translation and generates a report

These reports can be given to the Customer Service Department or the cable plant’s Operations and Maintenance Department. Using these reports, maintenance personnel can quickly discern how characteristic patterns of flappingcable modems, street addresses, and flap statistics can indicate which amplifieror feeder lines are faulty. The reports also help you quickly discern whether problems exist in your downstream or upstream path, and whether the problem is ingress noise or equipment related.

Default values for the following flap-list configuration commands are:

• cable flap-list miss-threshold—6 seconds

• cable flap-list power-adjust—2 dB

• cable flap-list insertion-time—180 seconds

Troubleshooting Using Cable Flap Lists

78-5897-01

Note Since the cableflaplistwasoriginallydeveloped, polling mechanisms have been enhanced

since Cisco IOS Release 11.3.7 NA to have an increased rate of 1/sec when polls are missed. Cable modems go offlinefaster than the frequency hop period. This can cause the frequency to stay fixed while cable modems go offline. To compensate for this, as appropriate, you can reduce the hop period to 10 seconds.

Cisco uBR7200 Series Universal Broadband Router Software Configuration Guide

4-35

Troubleshooting Using Cable Flap Lists

Tips In Cisco IOS Release 12.0(7)XR2, Cisco IOS Release 12.1(1a)T1, and higher,the system

supports automatic power adjustments. The show cable flap-list and show cable modem commands now indicate when the Cisco uBR7200 series router has detected an unstable return path for a particular modem and has compensated with a power adjustment. An asterisk appears in the power adjustment field for a modem when a power adjustment has been made; an exclamation point appears when the modem has reached its maximum power transmit level and cannot increase its power level any further.

The following tips and scenarios allow you to use the flap list in the most effective way:

• If a subscriber's cable modem shows a lot of flap list activity, it is having communication problems.

• If a subscriber's cable modem shows little or no flap list activity, it is communicating reliably; the

problem is probably in the subscriber's computer equipment or in the connection to the cable modem.

• The top 10% most active cable modems in the flap list are most likely to have difficulties

communicating with the headend.

• Cable modems with more than 50 power adjustments per day have a suspect upstream path.

• Cable modems with approximately the same number of hits and misses and with a lot of insertions

have a suspect downstream path (for example, low level into the cable modem).

• All cable modems incrementing the insertion at the same time indicates a provisioning server

failure.

• Cable modems with high CRC errors have bad upstream paths or in-home wiring problems.

• Correlating cable modems on the same physical upstream port with similar flap list statistics can

quickly resolve outside plant problems to a particular node or geography.

• Monitoring the flap list cannot affect cable modem communications.

• The flap list should be saved to a database computer and cleared at least once a day.

• Important upstream performance data can be obtained by tracking flap list trend data.

• Important installation quality control and performance data is directly available from the flap list.

Chapter 4 Troubleshooting the System

4-36

Cisco uBR7200 Series Universal Broadband Router Software Configuration Guide

78-5897-01

Chapter 4 Troubleshooting the System

Following is a sample response to the show cable flap command:

uBR7200#show cable flap

Mac Addr CableIF Ins Hit Miss CRC P-Adj Flap Time

0010.9500.461f C3/0 U1 56 18857 887 0 1 116 Jun 1 14:09:12

0010.9500.446e C3/0 U1 38 18686 2935 0 1 80 Jun 2 19:03:57

0010.9500.38ec C3/0 U2 63 18932 1040 0 8 138 Jun 2 23:50:53

0010.9500.4474 C3/0 U2 65 18913 1053 0 3 137 Jun 2 09:30:09

0010.9500.4672 C3/0 U2 56 18990 2327 0 6 124 Jun 2 10:44:14

0010.9500.38f0 C3/0 U2 50 18964 2083 0 5 111 Jun 2 20:46:56

0010.9500.e8cb C3/0 U2 0 6537 183 0 1 5 Jun 2 22:35:48

0010.9500.38f6 C3/0 U3 50 19016 2511 0 2 104 Jun 2 07:46:31

0010.9500.4671 C3/0 U4 43 18755 3212 1 1 89 Jun 1 19:36:20

0010.9500.38eb C4/0 U0 57 36133 1608 0 6 126 Jun 2 20:04:58

0010.9500.3ce2 C4/0 U0 44 35315 1907 0 4 99 Jun 2 16:42:47

0010.9500.e8d0 C4/0 U2 0 13213 246 0 1 5 Jun 3 04:15:30

0010.9500.4674 C4/0 U4 56 36037 2379 0 4 121 Jun 3 00:34:12

0010.9500.4677 C4/0 U4 40 35781 2381 0 4 91 Jun 2 12:14:38

0010.9500.4614 C5/0 U5 40 21810 2362 0 502 586 Jun 2 21:43:02

0010.9500.3be9 C6/0 U5 63 22862 969 0 0 128 Jun 1 14:09:03

0010.9500.4609 C6/0 U5 55 22723 2127 0 0 112 Jun 1 14:08:02

0010.9500.3cb8 C6/0 U5 49 22607 1378 0 0 102 Jun 1 14:08:58

0010.9500.460d C6/0 U5 46 22477 2967 0 2 96 Jun 2 17:03:48

0010.9500.3cba C6/0 U5 39 22343 3058 0 0 81 Jun 1 14:13:16

0010.9500.3cb4 C6/0 U5 38 22238 2936 0 0 79 Jun 1 14:09:26

0010.9500.4612 C6/0 U5 38 22306 2928 0 0 79 Jun 1 14:09:29

Troubleshooting Using Cable Flap Lists

The command line with an arrow next to it reveals a cable modem that is continuously flapping. A high flaprate indicates that the cable modem is power adjusting frequently. This can indicate a problem with an amplifier. The number reveals the number of times the CMTS instructed the cable modem to adjust the transmit power more than 3 dB.

Cable modems are automatically added to the flap list when any of the following conditions are detected:

• When the cable modem re-registers more frequently than the user-specified insertion time.

• When intermittent keepalive messages are detected between the CMTS and the cable modem.

• When the cable modem’s upstream transmit power is adjusted beyond the user-specified power

Display the Flap List

The flap list can be queried either using the standard Simple Network Management (SNMP) API or the CLI. Using any thirdparty SNMP Management Information Base (MIB) browser, you can query the ccsFlapTable in the CISCO-CABLE-SPECTRUM-MIB, a proprietary extension to the DOCSIS MIBs.

Using the show cable flap list command, the flap list statistics are accessed. A sample appears below. Each of the columns in the display are described in Table 4-20:

0010.7b6b.60ad C3/0 U0 0 14386 1390 1 38 41 Nov 24 21:34:24

0010.7b6b.65a3 C3/0 U0 0 14503 1264 1 33 37 Nov 24 21:28:09

0010.7b6b.6b9d C3/0 U0 0 14060 1726 3 40 43 Nov 24 21:18:36

threshold.

MAC ID___ CableIF Ins _Hit__ Miss CRC P-Adj Flap ___Time____

78-5897-01

Cisco uBR7200 Series Universal Broadband Router Software Configuration Guide

4-37

Chapter 4 Troubleshooting the System

Troubleshooting Using Cable Flap Lists

Table 4-20 Flap List Statistics Description

Statistic Description

MAC ID This is the MAC-layer address of a cable modem. The first six digits indicate the vendor ID of

the cable modem manufacturer, followed by six digits indicating a unique host address. Each cable modem's MAC address is unique.

Cable IF This is the physical upstream interface on the Cisco uBR7200. It denotes the cable modem card

slot number, the downstream port number on the RF line card and the upstream port number on the same cable modem card. The flap list data can be sorted based on the upstream port number which is useful when isolating reverse path problems unique to certain combining groups.

Insertions Link insertion is the process whereby a modem performs an initial maintenance procedure to

establish link with the CMTS. The Ins column is the flapping modem’s insertion count and indicates the number of times the RF link was abnormally re-established. An abnormality is detected when the time between link re-establishment attempts is less than the user-configurable parameter.

Normal modem activity follows the sequence below.

• The initial link insertion is followed by a keepalive loop between the CMTS and cable

modem and is called station maintenance.

• Power-on

• Initial maintenance

• Station maintenance

• Power-off

When the link is broken, initial maintenance is repeated to re-establish the link. Initial maintenance @ Time T1 Station maintenance Init maintenance @ Time T2 The Ins and Flap counters in the flaplist are incremented whenever T2 – T1 < N where N is the

insertion-time parameter configured in <cable flap-list insertion-time>. Default value for this parameter is TBD seconds.

A high Ins number indicates:

• Intermittent downstream sync loss

• DHCP or modem registration problems

4-38

Cisco uBR7200 Series Universal Broadband Router Software Configuration Guide

78-5897-01

Chapter 4 Troubleshooting the System

Troubleshooting Using Cable Flap Lists

Table 4-20 Flap List Statistics Description

Hit and Miss The HIT and MISS columns are keepalive polling statistics between the Cisco uBR7200 series

and the cable modem. The station maintenance process occurs for every modem approximately every 25 seconds. When the CMTS receives a response from the modem, the event is counted as a Hit. If the CMTS does not receive a response from the cable modem, the event is counted as a Miss. A cable modem will fail to respond either because of noise or if it is down. Modems which only log Misses and zero Hits are assumed to be powered off.

Misses are not desirable since this is usually an indication of a return path problem; however, having a small number of misses is normal. The flap count is incremented if there are M consecutive misses where M is configured in the cable flap miss-threshold parameter. The parameter value ranges from 1 to 12 with a default of 6.

Ideally,theHIT count should be much greater than the Miss counts. If a modem has a HIT count much less than its MISS count, then registration is failing. Noisy linkscause the MISS/HIT ratio to deviate from a nominal 1% or less. High Miss counts can indicate:

• Intermittent upstream possibly due to noise

• Laser clipping

• Common-path distortion

• Ingress or interference

• Too much or too little upstream attenuation

Cyclical RedundancyCheck (CRC)

Power Adjustments (P-Adj)

This statistic tracks the CRC error counter per modem. CRC errors are usually an indication of noise on a plant. A low count can be always be expected but a high CRC number calls for some the plant troubleshooting. The CRC counter indicates:

• Intermittent upstream

• Laser clipping

• Common-path distortion

• Impulsive noise or interference

The station maintenance poll in the CMTS constantly adjusts the modem transmit power, frequency, and timing. The P-Adj column indicates the number of times the modem’s power adjustment exceeded the threshold value. The power adjustment threshold may be set using the <cable flap power threshold > parameter with a value range of 0 to 10 dB and a default value of 2 dB. Tuning this threshold is recommended to decrease irrelevant entries in the flap list. Power Adjustment values of 2 dB and below will continuously increment the P-Adj counter. The modem transmitter step size is 1.5 dB, whereas the headend may command 0.25 dB step sizes. Power adjustment flap strongly suggests upstream plant problems such as:

• Amplifier degradation

• Poor connections

• Thermal sensitivity

• Attenuation problem

78-5897-01

Cisco uBR7200 Series Universal Broadband Router Software Configuration Guide

4-39

Chapter 4 Troubleshooting the System

Troubleshooting Using Cable Flap Lists

Table 4-20 Flap List Statistics Description

Flap The Flap counter indicates the number of times the modem has flapped. This counter is

incremented when one of the following events is detected: Unusual modem insertion or reregistration attempts. The Flap and the Ins counters are

incremented when the modem tries to reestablish the RF link with the CMTS within a period of time that is less than the user-configurable insertion interval value.

Abnormal Miss/Hit ratio The Flap counter is incremented when N consecutive Misses are detected after a Hit where N can be user-configurable with a default value of 6.

Unusual power adjustment The Flap and P-adj counters are incremented when the modem’s upstream power is adjusted beyond a user-configurable power level.

Time Time is the timestamp indicating the last time the modem flapped. The value is based on the

clock configured on the local Cisco uBR7200 series. If no time is configured, this value is based on the current uptime of the Cisco uBR7200 series. When a modem meets one of the three flap list criteria, the Flap counter is incremented and Time is set to the current time.

Troubleshoot with the Flap List

This section includes suggestions on how to interpret different network conditions based on the flaplist statistics:

• Condition 1: Low miss/hit ratio (< 10% for MC11 card, < 2% for MC16 card), low insertion, low

P-adj, low flap counter and old timestamp.

Analysis: This exhibits an optimal network situation.

• Condition 2: High ratio of misses over hits (> 10%)

Analysis: Hit/miss analysis should be done after the "Ins" count stops incrementing. In general, if

the hit and miss counts are about the same order of magnitude, then the upstream may be experiencingnoise. If the miss count is greater, then the modem is probablydropping out frequently and not completing registration. The upstream or downstream is perhaps not stable enough for reliable link establishment. Very low hits and miss counters and high insertion counters indicate provisioning problems.

• Condition 3: Relatively high power adjustment counter.

Analysis: Indicates the power adjustment threshold is probably set at default value of 2 dB

adjustment. The modem transmitter step size is 1.5 dB, whereas the headend may command

0.25 dB step sizes. Tuning your power threshold to 6 dB is recommended to decrease irrelevant entries in the flap list. The power adjustment threshold may be set using <cable flap power threshold <0-10 dB>> from the Cisco IOS global configuration mode. A properly operating HFC network with short amplifier cascades can use a 2-3 dB threshold.

• Condition 4: High P-Adj and CRC errors.

Analysis: This condition can indicate that the fiber node is clipping the upstream return laser.

Evaluate the modems with the highest CRC count first. If the modems are not going offline (Ins = 0), this will not be noticed by the subscriber. However, they could receive slower service due to dropped IP packets in the upstream. This condition will also result in input errors on the Cisco uBR7200 series cable interface.

• Condition 5: High insertion rate.

Analysis: If link re-establishment happens too frequently, then the modem is usually having a

registration problem.This is indicated by a high ‘Ins’ counter which tracks the ‘Flap’ counter.

4-40

Cisco uBR7200 Series Universal Broadband Router Software Configuration Guide

78-5897-01

Chapter 4 Troubleshooting the System

Set Cable Flap List Aging

You can specify the number of days to record and retain flapping activity on cable modems currently in the flap-list table. This value is known as the age of the flap list. The valid range is from 1 to 60 days.

To set the age of the flap list, use the following command in global configuration mode.

Table 4-21 Instructions to Set Cable Flap List Aging

Command Purpose

CMTS01(config)# cable flap-list aging days

Verify Cable Flap List Aging

To verify that cable flap list aging is set, enter the show cable flap list command:

CMTS01# show cable flap list Mac Addr CableIF Ins Hit Miss CRC P-Adj Flap Time

0010.7b6b.5d1d C3/0 U0 0 688 169 0 0 3 Nov 5 12:28:50

0010.7b6b.5e15 C3/0 U0 1 707 185 0 0 5 Nov 5 12:29:52

0010.7b6b.5e27 C3/0 U0 1 707 198 0 0 5 Nov 5 12:29:55

0010.7b6b.5d29 C3/0 U0 1 709 205 0 0 5 Nov 5 12:29:52

0010.7b6b.5e2b C3/0 U0 1 710 204 0 0 7 Nov 5 12:30:16

Specify the number of days to record and retain flapping activity for the cable modems connected to this Cisco uBR7200 series.

Troubleshooting Using Cable Flap Lists

Set Cable Flap List Insertion Time

You can set the cable flap list insertion time. When a cable modem makes an insertion request more frequently than the amount of insertion time defined by this command, the cable modem is placed in the flap list for activity recording. The valid range is from 60 to 86400 seconds.

To set the cable flap list insertion time, use the following command in global configuration mode.

Table 4-22 Instructions to Set Cable Flap List Insertion Time

Command Purpose

CMTS01(config)# cable flap-list insertion-time seconds

Verify Cable Flap List Insertion Time

To verify cable flap list insertion time, enter the show cable flap list command:

CMTS01# show cable flap list Mac Addr CableIF Ins Hit Miss CRC P-Adj Flap Time

0010.7b6b.5d1d C3/0 U0 0 688 169 0 0 3 Nov 5 12:28:50

0010.7b6b.5e15 C3/0 U0 1 707 185 0 0 5 Nov 5 12:29:52

0010.7b6b.5e27 C3/0 U0 1 707 198 0 0 5 Nov 5 12:29:55

0010.7b6b.5d29 C3/0 U0 1 709 205 0 0 5 Nov 5 12:29:52

0010.7b6b.5e2b C3/0 U0 1 710 204 0 0 7 Nov 5 12:30:16

Specify the insertion time in seconds. Any cable modem that makes an insertion request more frequently than this period of time is placed in the flap list.

78-5897-01

Cisco uBR7200 Series Universal Broadband Router Software Configuration Guide

4-41

Chapter 4 Troubleshooting the System

Troubleshooting Using Cable Flap Lists

Set Cable Flap List Power Adjustment Threshold

You can specify the power adjustment threshold that will cause a flap-list event to be recorded. When the power adjustment of a cable modem meets or exceeds the threshold, the cable modem is placed in the flap list. The valid range is from 1 to 10 dBmV.

Note A power adjustment threshold of less than 2 dBmV might cause excessive flap list event

recording. Cisco recommends setting this threshold value to 3 dBmV or higher.

To set the power adjustment threshold for flap-list events, use the following command in global configuration mode.

Table 4-23 Instruction to Set Cable Flap List Power Adjustment Threshold

Command Purpose

CMTS01(config)# cable flap-list power-adjust threshold dbmv Specify the minimum power adjustment that will

constitute a flap-list event.

Verify Cable Flap List Power Adjustment Threshold

To verify the cable flap list power adjustment threshold, enter the show cable flap list command:

CMTS01# show cable flap list Mac Addr CableIF Ins Hit Miss CRC P-Adj Flap Time

0010.7b6b.5d1d C3/0 U0 0 688 169 0 0 3 Nov 5 12:28:50

0010.7b6b.5e15 C3/0 U0 1 707 185 0 0 5 Nov 5 12:29:52

0010.7b6b.5e27 C3/0 U0 1 707 198 0 0 5 Nov 5 12:29:55

0010.7b6b.5d29 C3/0 U0 1 709 205 0 0 5 Nov 5 12:29:52

0010.7b6b.5e2b C3/0 U0 1 710 204 0 0 7 Nov 5 12:30:16

Set Cable Flap List Miss Threshold

You can specify the miss threshold for recording a flap-list event. A miss is the number of times a cable modem does not acknowledge a MAC layer keepalivemessage from a cable modem card. An 8% miss rate is normal for the Cisco cable modem cards.When the number of misses exceeds the threshold, the cable modem is placed in the flap list.

Note A high miss rate can indicate intermittent upstream problems, fiber laser clipping, or

common-path distortion.

To set the miss threshold for recording a flap-list event, use the following command in global configuration mode.

Table 4-24 Instructions to Set Cable Flap List Miss Threshold

Command Purpose

CMTS01(config)# cable flap-list miss-threshold misses Specify the number of MAC-layer keepalive misses

that will result in the cable modems being place in the flap list.

Cisco uBR7200 Series Universal Broadband Router Software Configuration Guide

4-42

78-5897-01

Chapter 4 Troubleshooting the System

Verify Cable Flap List Miss Threshold

To verify the cable flap list miss threshold, enter the show cable flap list command:

CMTS01# show cable flap list Mac Addr CableIF Ins Hit Miss CRC P-Adj Flap Time

0010.7b6b.5d1d C3/0 U0 0 688 169 0 0 3 Nov 5 12:28:50

0010.7b6b.5e15 C3/0 U0 1 707 185 0 0 5 Nov 5 12:29:52

0010.7b6b.5e27 C3/0 U0 1 707 198 0 0 5 Nov 5 12:29:55

0010.7b6b.5d29 C3/0 U0 1 709 205 0 0 5 Nov 5 12:29:52

0010.7b6b.5e2b C3/0 U0 1 710 204 0 0 7 Nov 5 12:30:16

Set Cable Flap List Size

You can specify the maximum number of cable modems that can be listed in the cable flap list tables. The valid range is from 1 to 8192 cable modems. The default is 8192 cable modems.

To specify the maximum number of cable modems that can be recorded in the flap list, use the following command in global configuration mode.

Table 4-25 Instructions to Set Cable Flap List Size

Troubleshooting Using Cable Flap Lists

Command Purpose

CMTS01(config)# cable flap-list size number

Specify the maximum size of the flap list.

Verify Cable Flap List Size

To verify the cable flap list size, enter the show cable flap list command:

CMTS01# show cable flap list Mac Addr CableIF Ins Hit Miss CRC P-Adj Flap Time

0010.7b6b.5d1d C3/0 U0 0 688 169 0 0 3 Nov 5 12:28:50

0010.7b6b.5e15 C3/0 U0 1 707 185 0 0 5 Nov 5 12:29:52

0010.7b6b.5e27 C3/0 U0 1 707 198 0 0 5 Nov 5 12:29:55

0010.7b6b.5d29 C3/0 U0 1 709 205 0 0 5 Nov 5 12:29:52

0010.7b6b.5e2b C3/0 U0 1 710 204 0 0 7 Nov 5 12:30:16

Clear Cable Flap List

To remove a single cable modem from the flap list or to removeall cable modems from the flap list, use one of the following commands in global configuration mode.

Table 4-26 Instructions to Clear Cable Flap List

Command Purpose

CMTS01(config)# clear cable flap-list mac-addr

Clear the entries in the cable flap list for the cable modem with this MAC address.

CMTS01(config)# clear cable flap-list all

Cisco uBR7200 Series Universal Broadband Router Software Configuration Guide

78-5897-01

Clear the entries for all of the cable modems in the flap list.

4-43

Chapter 4 Troubleshooting the System

Troubleshooting Using Cable Flap Lists

Customize Other Flap List Values and Related Commands

The following displays flap list with different sorting options:

show cable modem flap-list [cable <n> | sort-flap | sort-time | sort-interface]

The following sets the threshold value for link establishment:

[no] cable flap-list insertion-time <sec>

Note A modem is tagged as flappingif the insertion time exceeds this value. Its value can be set

from 60 to 86400 seconds with a default of 180 seconds.

The following sets the number of consecutive missed station maintenance(RNG-RSP) messages that must be missed for a ‘flap’ event to occur. Value ranges from 1-12 with a default of 6 seconds. The hits and miss counters are not affected:

[no] cable flap-list miss-threshold <miss-threshold>

The following clears the counters for a cable modem (or all cable modems) in the station maintenance list:

clear cable modem { <mac-addr> | <ip-addr> | all } counters

The following displays the QoS, modem status, In and Out octets, IP and MAC addresses per SID: show int cable slot/port sid

The following drops the modem's RF link by removing a modem from the keep-alive polling list. This forces the modem to reset:

clear cable-modem { <mac-addr> | <ip-addr> | all } reset

The following uses a MAC layer ping to determine if the cable modem is online. It uses smaller data units on the wire than a standard IP ping, resulting in lower overhead. Works even if the IP layer in the modem is down or hasn’t completed registration:

ping DOCSIS cable-modem <mac-addr | IP address >

The following displays the timing offset, receive power, and QoS values by cable interface, SID, and MAC address:

show cable modem [<ip-address> | <MAC-address>]

The following displays the current allocation table and frequency assignments:

show cable spectrum-group [spectrum group number]

The following displays maximum, average, and minimum% online time and offline times for a given SID on a given Cisco uBR7200 interface:

show int slot/port sid connectivity

4-44

The following displays input and output rates, input errors, CRC, frames, overruns, underruns, collisions, interface resets. High input errors in the CMTS retrieved from this query suggests noisy upstream. In older versions of the chassis, loose midplane and line card screws caused a similar problem:

show interface slot/downstream-port

Cisco uBR7200 Series Universal Broadband Router Software Configuration Guide

78-5897-01

Chapter 4 Troubleshooting the System

Performing Amplitude Averaging

The Cisco uBR7200 series uses an averaging algorithm to determine the optimum power level for a cable modem with low carrier-to-noise ratio that is making excessive power adjustments—known as flapping. To avoid dropping flapping cable modems, the Cisco uBR7200 series universal broadband router averages a configurable number of RNG-REQ messages before it makes power adjustments. By compensating for a potentially unstable return path, the Cisco uBR7200 series router maintains connectivity with affected cable modems. You can interpret these power adjustments, however, as indicating unstable return path connections.

The show cable flap-list and show cable modem commands are expanded to indicate which paths the Cisco uBR7200 series is making power adjustments and which modems have reached maximum transmit power settings. These conditions indicate unstable paths that should be serviced.

The following example shows the output of the show cable flap-list command:

router# show cable flap-list MAC Address Upstream Ins Hit Miss CRC P-Adj Flap Time

0010.7bb3.fd19 Cable5/0/U1 0 2792 281 0 *45 58 Jul 27 16:54:50

0010.7bb3.fcfc Cable5/0/U1 0 19 4 0 !43 43 Jul 27 16:55:01

0010.7bb3.fcdd Cable5/0/U1 0 19 4 0 *3 3 Jul 27 16:55:01

Performing Amplitude Averaging

The * symbol indicates that the CMTS is using the power adjustment method on this modem. The ! symbol indicates that the modem has reached maximum transmit power.

Output of the show cable modem command appears below:

Similar to the showcable flap-listdisplay, the * symbol in the show cable modem output indicates that the CMTS is using the power adjustment method on this CM. The ! symbol indicates that the CM has reached maximum transmit power.

This section documents the commands pertaining to amplitude averaging:

• cable upstream power-adjust noise

• cable upstream frequency-adjust averaging

Enable or Disable Power Adjustment

To enable or disable the power adjustment capability, use the following commands:

cable upstream n power-adjust {threshold [threshold #] | continue [tolerable value] | noise [%

of power adjustment]}

no cable upstream power-adjust

Cisco uBR7200 Series Universal Broadband Router Software Configuration Guide

78-5897-01

4-45

Performing Amplitude Averaging

Table 4-27 Cable Upstream Power Adjust Syntax Descriptions

Syntax Valid Values

n Specifies the upstream port number. threshold # Specifiesthe poweradjustment threshold. The threshold range is from

tolerable value Determines if the status of the RNG-RSPshould beset to CONTINUE

% of power adjustment Specifies the percentage of power adjustment packets required to

Note The threshold default is 1 dB. The tolerable value default is 2 dB. The power adjustment

is 30 percent.

Chapter 4 Troubleshooting the System

0 through 10 dB. The default is 1 dB.

or SUCCESS. The range is from 2 through 15 dB. The default is 2 dB.

switch from the regular power adjustment method to the noise power adjustment method. Range is from 10 through 100 percent. The default is 30 percent.

Caution Default settings are adequate for system operation. Amplitude averaging is an automatic

procedure. In general, Cisco does not recommend you adjust values. Cisco does recommend, however, that you clean up your cable plant should you encounter flapping cable modems.

Note In some instances, you might adjust certain values:

If CMs cannot complete ranging because they have reached maximum power levels, you might try to set the tolerable value CONTINUE field to a larger value than the default of 2 dB. Values larger than 10 dB on “C” versions of cable modem cards, or 5 dB on FPGA versions, are not recommended.

If the flap list shows CMs with a large number of power adjustments, but the CMs are not detected as “noisy,” you might try to decrease the percentage for “noisy.” If you think too many CMs are unnecessarily detected as “noisy,” you might try to increase it.

Set Frequency Threshold to Affect Power Adjustment

To control power adjustment methods by setting the frequency threshold, use the cable upstream freq-adj averaging interface configuration command. To disable power adjustments, use the no form

of this command.

4-46

cable upstream n freq-adj averaging % of frequency adjustment no cable upstream freq-adj averaging

Cisco uBR7200 Series Universal Broadband Router Software Configuration Guide

78-5897-01

Chapter 4 Troubleshooting the System

Table 4-28 Cable Upstream Freq-adj Averaging Syntax Descriptions

Syntax Valid Values

n Specifies the upstream port number. averaging Specifies that a percentage of frequency adjustment packets is

required to change the adjustment method from the regular power adjustment method to the noise power adjustment method.

% of frequency adjustment Specifies the percentage of frequency adjustment packets required to

switch from the regular power adjustment method to the noise power adjustment method. Valid range is from 10 through 100 percent.

The following example shows how to change the power adjustment method when the frequency adjustment packet count reaches 50 percent:

router(config-if)# cable upstream 0 freq-adj averaging 50

Setting Downstream Test Signals

This feature provides configuration commands that allow you to create downstream test signals. Both Pseudo Random Bit Stream (PRBS) and unmodulated carrier test signals are now supported.

A PRBS test signal is a random data pattern that has been modulated to look like a real data stream. An unmodulated test signal is a continuous sine wave that looks like a carrier wave on the downstream transmission.

See the following required tasks to create PRBS and unmodulated carrier test signals:

• Configure Unmodulated Test Signals

• Configure PRBS Test Signals

Configure Unmodulated Test Signals

Table 4-29 Instructions to Conﬁgure Unmodulated Test Signals

Step Command Purpose

# router(config-if)# cable downstream if-output

continuous-wave

Router(config-if)# no cable downstream if-output

Generatesanunmodulated continuous-wave signal on the downstream channel. The interface is shut down.

Stops sending test signals.

Note Remember to reenable the

interface to resume normal operations.

78-5897-01

Cisco uBR7200 Series Universal Broadband Router Software Configuration Guide

4-47

Pinging Unresponsive Cable Modems

Configure PRBS Test Signals

Table 4-30 Instructions to Conﬁgure PRBS Test Signals

Step Command Purpose

# router(config-if)# cable downstream if-output prbs

Router(config-if)# no cable downstream if-output

Generates a PRBS test signal on the downstream channel. The interface is shut down.

Stops sending test signals.

Note Remember to reenable the

Verify Test Signal Output

Chapter 4 Troubleshooting the System

interface to resume normal operations.

To verify the output of a continuous-wave test signal or the output of a PRBS test signal, use a spectrum analyzer on the downstream channel. The downstream carrier is enabled as a default.

The standard mode of operation is modulated signal output and the interface is active. For PRBS and continuous wave output, the selected interface will be shut down.

The functioning of the no cabledownstreamif-output commandhas not changed. The interface is shut down.

Pinging Unresponsive Cable Modems

Ping a Cable Modem

Ping DOCSIS is a Cisco patent-pending feature that allows a cable system administrator to quickly diagnose the health of a channel between the Cisco uBR7200 series universal broadband router and the cable modem. The technology uses 1/64—the bandwidth of IP ping—and works with cable modems that don’t have an IP address. This allows cable operators to ping cable modems that are unable to complete registration, have internal bugs, or that are unresponsive due to a crash.

Information the Ping DOCSIS feature includes a real-time view and plot of requested power adjustments, as well as a measure of optimal headend reception power.This givesthe cable operator the ability to solicit a configurable number of periodic ranging requests from a cable modem.

To ping a specificcable modem to determine if it is online, use the following command in EXEC mode.

Table 4-31 Instructions to Ping a Cable Modem

Command Purpose

CMTS01# ping docsis

Cisco uBR7200 Series Universal Broadband Router Software Configuration Guide

4-48

addr

Ping the cable modem with a specific MAC address or IP address to see if it is online.

78-5897-01

Chapter 4 Troubleshooting the System

Verify the Ping

The ping docsis command returns a verification from a cable modem that is pinged:

Queueing 5 MAC-layer station maintenance intervals, timeout is 25 msec: !!!!! Success rate is 100 percent (5/5)

Tips If you are having trouble, make sure you are using a valid MAC or IP address for the

cable modem you want to ping.

Using Cable Interface Debug Commands

To troubleshoot cable interfaces, use the following debug commands in enable (privileged EXEC) mode.

Table 4-32 Instructions to Use Debug Command

Command Purpose

CMTS01# debug cable ? CMTS01# undebug all

View all debug cable commands that are available. Turn off all debugging information to the console

and choose a more selective debug command.

Using Cable Interface Debug Commands

Caution The following commands can generate large amounts of output as the number of

cable modems grows. On heavily loaded systems with thousands of cable modems, these commands can dramatically affect router performance.

Debug Cable ARP Requests

This command activates debugging of arp requests on the cable interfaces. When this command is activated, all cable arp request messages are displayed on the Cisco uBR7200 series console. The format for the command follows:

CMTS01# debug cable arp

To deactivate debugging of arp requests, use the following command:

CMTS01# no debug cable arp

Note Refer to the debug commands

that follow.

78-5897-01

Cisco uBR7200 Series Universal Broadband Router Software Configuration Guide

4-49

Using Cable Interface Debug Commands

Debug Environmental Monitor Messages

This command activates debugging of the Cisco uBR7200 series environmental monitor. When this command is activated, all environmental monitor messages are displayed on the Cisco uBR7200 series console. The format for the command follows:

CMTS01# debug cable envm

To deactivate debugging of the environmental monitor, use the following command:

CMTS01# no debug cable envm

Debug Cable MAC Protocol Errors

This command activates debugging of cable MAC protocol errors. When this command is activated, any errors that occur in the cable MAC protocol are displayed on the Cisco uBR7200 series console. The format for the command follows:

CMTS01# debug cable err

To deactivate debugging of MAC protocol errors, use the following command:

CMTS01# no debug cable err

Chapter 4 Troubleshooting the System

Activate Debug of Baseline Privacy

This command activates debugging of baseline privacy. The format for the command follows:

CMTS01# debug cable privacy

To deactivate debugging of baseline privacy, use the following command:

CMTS01# no debug cable privacy

Debug Baseline Privacy Activity

This command activatesdebugging of the tek andkek baseline privacy key activity. When this command is activated, all activity related to kek and tek keys is displayed on the Cisco uBR7200 series console. The format for the command follows:

CMTS01# debug cable keyman

To deactivate debugging of the keys, use the following command:

CMTS01# no debug cable keyman

Debug Cable MAC Messages

This command activates debugging of messages generated in the cable MAC that frames and encrypts downstream RF signals. When this command is activated, messages generated by the cable MAC are displayed on the Cisco uBR7200 series console. The format for the command follows:

CMTS01# debug cable mac-messages

4-50

Cisco uBR7200 Series Universal Broadband Router Software Configuration Guide

78-5897-01

Chapter 4 Troubleshooting the System

To deactivate debugging of cable MAC messages, use the following command:

CMTS01# no debug cable mac-messages

Debug Cable Maps

This command activates debugging of cable maps that identify data on cable interfaces. When this command is activated, messages related to cable maps are displayed on the Cisco uBR7200 series console. The format for the command follows:

CMTS01# debug cable map

To deactivate debugging of cable maps, use the following command:

CMTS01# no debug cable map

Debug Cable Modems

This command activates debugging of cable modems. When this command is activated, messages from cable modems on the HFC network are displayed on the Cisco uBR7200 series console. The format for the command follows:

CMTS01# debug cable modems

Using Cable Interface Debug Commands

To deactivate debugging of cable MAC messages, use the following command:

CMTS01# no debug cable modems

Debug Cable PHY Messages

This command activates debugging of messages generated in the cable PHY—the physical layer where upstream and downstream activity between the Cisco uBR7200 series and the HFC network is controlled. When this command is activated, messages generated in the cable PHY are displayed on the Cisco uBR7200 series console. The format for the command follows:

CMTS01# debug cable phy

To deactivate debugging of the cable PHY, use the following command:

CMTS01# no debug cable phy

Activate QoS Debug

This command activates debugging of QoS. When this command is activated, messages related to QoS parameters are displayed on the Cisco uBR7200 series console. The format for the command follows:

CMTS01# debug cable qos

To deactivate debugging of QoS, use the following command:

CMTS01# no debug cable qos

78-5897-01

Cisco uBR7200 Series Universal Broadband Router Software Configuration Guide

4-51

Using Cable Interface Debug Commands

Debug Cable Modem Ranging Messages

This command activates debugging of ranging messages from cable modems on the HFC network. When this command is activated, ranging messages generated when cable modems request or change their upstream frequencies are displayed on the Cisco uBR7200 series console. The format for the command follows:

CMTS01# debug cable range

To deactivate debugging of cable modem ranging, use the following command:

CMTS01# no debug cable range

Debug Upstream Messages

This command activates debugging of upstream messages from cable modems. When this command is activated, any messages generated by cable modems and sent to the Cisco uBR7200 series will be displayed on the Cisco uBR7200 series console. The format for the command follows:

CMTS01# debug cable receive

Chapter 4 Troubleshooting the System

To deactivate debugging of upstream messages, use the following command:

CMTS01# no debug cable receive

Debug Cable Modem Registration Requests

This command activates debugging of registration requests from cable modems on the HFC network. When this command is activated, messages generated by cable modems as they make requests to connect to the network are displayed on the Cisco uBR7200 series console. The format for the command follows:

CMTS01# debug cable reg

To deactivate debugging of cable registration, use the following command:

CMTS01# no debug cable reg

Debug Cable Modem Reset Messages

This command activates debugging of reset messages from cable modems on the HFC network. When this command is activated, reset messages generated by cable modems are displayed on the Cisco uBR7200 series console. The format for the command follows:

CMTS01# debug cable reset

To deactivate debugging of cable reset messages, use the following command:

CMTS01# no debug cable reset

4-52

Cisco uBR7200 Series Universal Broadband Router Software Configuration Guide

78-5897-01

Chapter 4 Troubleshooting the System

Debug Spectrum Management

This command activates debugging of spectrum management (frequency agility) on the HFC network. When this command is activated,messages generated because of spectrum group activity are displayed on the Cisco uBR7200 series console. Spectrum group activity can be additions or changes to spectrum groups, or frequency and power level changes controlled by spectrum groups. The format for the command follows:

CMTS01# debug cable specmgmt

To deactivatedebugging of cable spectrum management, use the no debug cable specmgmt command:

CMTS01# no debug cable specmgmt

Debug Channel Allocations

This command activates debugging of channel allocations on the HFC network. When this command is activated, messages generated when channels are allocated to cable modems on the HFC network are displayed on the Cisco uBR7200 series console. The format for the command follows:

CMTS01# debug cable startalloc

Using Cable Interface Debug Commands

To deactivate debugging of cable channel allocations, use the no debug cable startalloc command:

CMTS01# no debug cable startalloc

Debug CMTS Transmissions

This command activates debugging of transmissions from the Cisco uBR7200 series across the HFC network. When this command is activated, messages generated at the headend are displayed on the Cisco uBR7200 series console. The format for the command follows:

CMTS01# debug cable transmit

To deactivate debugging of cable transmissions, use the no debug cable transmit command:

CMTS01# no debug cable transmit

Debug Upstream Channel Change (UCC) Messages

This command activates debugging of upstream channel change (UCC) messages generated when cable modems request or are assigned a new channel. When this command is activated, messages related to upstream channel changes are displayed on the Cisco uBR7200 series console. The format for the command follows:

CMTS01# debug cable ucc

To deactivate debugging of cable upstream channel changes, use the following command:

CMTS01# no debug cable ucc

78-5897-01

Cisco uBR7200 Series Universal Broadband Router Software Configuration Guide

4-53

Chapter 4 Troubleshooting the System

Managing the Cisco uBR7246 VXR Clock Card

Debug Upstream Channel Description (UCD) Messages

This command activates debugging of upstream channel descriptor (UCD) messages. UCD messages contain information about upstream channel characteristics and are sent to the cable modems on the HFC network. Cable modems that are configured to use enhanced upstream channels use these UCD messages to identify and select an enhanced upstream channel to use. When this command is activated, messages related to upstream channel descriptors are displayed on the Cisco uBR7200 series console. The format for the command is as follows:

CMTS01# debug cable ucd

To deactivate debugging of cable upstream channel descriptor, use the following command:

CMTS01# no debug cable ucd

Managing the Cisco uBR7246 VXR Clock Card

Cisco IOS Release 12.1(1a)T1 introduced clock card commands that included:

• cable clock clear-counters

• cable clock force

• cable clock source-midplane

• show cable clock

• show controllers clock-reference

Cisco IOS Release 12.1(1a)T1 modified commands to support clock card operation include:

• show diag

• show frame-clocks

• show tech support

• show version

Clear Clock Counters

To reset the counters that are displayed with the show controllers clock-reference command, use the cable clock clear-counters privileged EXEC command.

cable clock clear-counters

This command resets any counters that were displayed from the last time the show controllers clock-reference command was used.

4-54

Cisco uBR7200 Series Universal Broadband Router Software Configuration Guide

78-5897-01

Chapter 4 Troubleshooting the System

Force Alternate Clock

To select the external timing source when the clock card is in holdover mode, use the cable clock force global configurationcommand. Todisable the selection and return to the default, use the no form of this command.

cable clock force {primary | secondary} no cable clock force

Setting the cable clock to primary forces the primary source to act as the clock reference. Setting the cable clock to secondary forces the secondary source to act as the clock reference.

The clock card automatically uses the primary external source, if available. If the primary source fails, the clock card enters holdover mode and after a few seconds, switches to the secondary external source. The clock card switches back to the primary source when it becomes available.

Note This command overrides the default behavior of the clock card, when the clock card is in

holdover mode. If the clock card is not in holdover mode, this command is ignored. You cannot force the reference to a port if the clock card is in free-running mode. The clock card enters holdover mode if the forced reference is lost, even if the other external reference is available.

Managing the Cisco uBR7246 VXR Clock Card

Set Midplane TDM Clock as Primary Reference

To make the midplane TDM clock the primary timing reference for the clock card, use the cable clock source-midplane global configuration command. Todisable the selection and return to the default, use the no form of this command.

cable clock source-midplane

Note Because the clock card automatically provides the timing reference to the midplane TDM

clock, the midplane cannot in turn act as the reference for the clock card. This means that the cable clock source-midplane command does not take effect unless a port adapter is configured as the primary clock reference source for the midplane.

Caution Although the cable clock source-midplane command is configurable, it is ignored, until

a port adapter that can serve as the midplane clock reference source is supported in the Cisco uBR7246 VXR. Currently, there are no port adapters on the Cisco uBR7246 VXR that support this.

Display Clock Values

To display clock reference status information for the clock card, use the show cable clock privileged EXEC command:

show cable clock

78-5897-01

Cisco uBR7200 Series Universal Broadband Router Software Configuration Guide

4-55

Chapter 4 Troubleshooting the System

Managing the Cisco uBR7246 VXR Clock Card

The following sample output from the show cable clock command shows both external sources are available and the clock card is providing the clock reference:

Router# show cable clock Clockcard primary input is present Clockcard secondary input is present Cable clock reference is clockcard primary input

Cable3/0 Timestamp clock reference is from Clockcard Cable4/0 Timestamp clock reference is from Clockcard

Show Clock Hardware Information and Register Values

To display hardware information, register values, and current counters for the cable clock card, use the show controllers clock-reference privileged EXEC command.

show controllers clock-reference

Tips To reset the counters that are displayed with the show controllers clock-reference

command, use the Clear Clock Counters command.

The following is sample output from the show controllers clock-reference command:

Router# show controllers clock-reference National clock card with T1 controller Control register :0x4 Status register :0x54 LIU Config Register 0:0x0 LIU Config Register 1:0x0 1 events reported in 266636 seconds Primary active :1, LOS :0 Secondary active :0, LOS :1 Holdovers :0, HW faults :0

Show Clock Diagnostic Information

To display diagnostic information for the cable modem cards, use the show diag command in privileged EXEC mode.

Tips Use the show diag command to display diagnostic information about the port adapters

installed in the router. This command also displays information about the cable clock card, if installed.

4-56

Cisco uBR7200 Series Universal Broadband Router Software Configuration Guide

78-5897-01

Chapter 4 Troubleshooting the System

The following is sample output from the show diag command displaying diagnostic information for the cable clock card:

router# show diag Clockcard: National clock card with T1 controller EEPROM contents at hardware discovery: Hardware Revision :1.1 Part Number :800-05867-02 Board Revision :11 Deviation Number :0-0 Fab Version :02 PCB Serial Number :CAB04046NXV RMA Test History :00 RMA Number :0-0-0-0 RMA History :00 EEPROM format version 4 EEPROM contents (hex): 0x00:04 FF 40 01 AC 41 01 01 C0 46 03 20 00 16 EB 02 0x10:42 31 31 80 00 00 00 00 02 02 C1 8B 43 41 42 30 0x20:34 30 34 36 4E 58 56 03 00 81 00 00 00 00 04 00

Table 4-33 describes the fields shown in the show diag display.

Managing the Cisco uBR7246 VXR Clock Card

Table 4-33 Show Diag Parameter Descriptions

Field Description

National clock card with T1 controller The system has identified the cable clock card. EEPROM contents at hardware discovery EEPROM programmed data present when the system

identified the clock card. Hardware Revision Version number of the card. Part Number The part number of the card. Board Revision Revision number (signifying a minor revision) of the

card. Deviation Number Revisionnumber (signifying a minor deviation) of the

card. Fab Version Manufacturing fabrication version number. PCB Serial Number Serial number of the printed circuit board. RMA Test History Counter indicating how many times diagnostics have

been performed on this card. RMA Number Return material authorization number, which is an

administrative number assigned if the card needs to

be returned for repair. RMA History Counter indicating howmany times the card has been

returned and repaired. EEPROM format version Version number of the EEPROM format. EEPROM contents (hex) Dumps of EEPROM programmed data.

78-5897-01

Cisco uBR7200 Series Universal Broadband Router Software Configuration Guide

4-57

Managing the Cisco uBR7246 VXR Clock Card

Show Clock Frames

To display information aboutthe midplane TDM clock reference, usethe showframe-clocksprivileged EXEC command.

show frame-clocks

The following sample output from the show frame-clocks command shows that there are no clock sources configured and the clock card is the default clock source:

Router# show frame-clocks Priority 1 clock source:not configured input:none Priority 2 clock source:not configured input:none Priority 3 clock source:not configured input:none Priority 4 clock source:not configured input:none Current clock source:Clockcard, input:Primary, priority:5

Table 4-34 describes the fields shown in the show frame-clocks display:

Table 4-34 Show Frame-clocks Parameter Descriptions

Field Description

Priority 1-4 clock source The configuration of the four network clock sources. Current clock source The current clock source, its input, and priority. In this

Chapter 4 Troubleshooting the System

example, the clock card is providing the clock source.

Show General Information

To display general information about the router when reporting a problem, use the show tech-support privileged EXEC command.

show tech-support [page] [< password>]

The page option causes the output to display a page of information at a time. Use the Return key to display the next line of output or use the space bar to display the next page of information. If not used, the output scrolls (that is, does not stop for page breaks).

The password option leaves passwords and other security information in the output. If not used, passwords and other security-sensitive information in the output are replaced with the label “<removed>” (this is the default).

Use this command to help collect general information about the router when you are reporting a problem. This command displays the equivalent of the following show commands:

• show buffers

• show controllers

• show interfaces

• show running-config

• show processes cpu

• show processes memory

• show stacks

• show version

4-58

Cisco uBR7200 Series Universal Broadband Router Software Configuration Guide

78-5897-01

Cisco uBR7200 Troubleshooting

Specifications and Main Features

Frequently Asked Questions

User Manual