Installation guide

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Cisco uBR7100 Series Universal Broadband Router Software Configuration Guide
OL-2238-03
Chapter 5 Troubleshooting the System
Pinging Unresponsive Cable Modems
Pinging Unresponsive Cable Modems
Pinging 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 uBR7100 series and the cable interface. The
technology uses 1/64—the bandwidth of IP ping—and works with cable modems that do not 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.
The Ping DOCSIS feature includes a real time view and plot of requested power adjustments, and a
measure of optimal headend reception power. This gives the cable operator the ability to solicit a
configurable number of periodic ranging requests from a cable interface.
To ping a specific cable interface to determine if it is online, use the following command in EXEC mode.
Verifying the Ping
The ping docsis command returns a verification from a cable modem that is pinged:
Queuing 5 MAC-layer station maintenance intervals, timeout is 25 msec:
!!!!!
Success rate is 100 percent (5/5)
Tip If you are having trouble, make sure you are using a valid MAC or IP address for the cable interface you
want to ping.
Using the Cable Monitor Feature
The Cable Monitor feature configures the cable interface so that it forwards copies of certain packets to a
specified interface (typically one of the fixed Fast Ethernet ports on the Cisco uBR7100 series router). By
attaching a network analyzer on that interface, you can monitor inbound or outbound packets for specific
types of traffic. This can provide invaluable information about the type of traffic being sent or received, and
whether that traffic contains any errors or unusual characteristics.
Note Do not confuse the Cable Monitor feature that is available on the Cisco uBR7100 series router with the
Cable Monitor feature available on Cisco cable CPE devices, such as the Cisco uBR924 cable access
router. The CMTS feature allows the analysis of traffic over the cable interface, while the cable CPE
version of this command provides a way for customers to obtain current configuration information when
the CPE cable interface goes down.
The cable monitor cable interface command has the following syntax:
Table 5-13 Instructions to Ping a Cable Modem
Command Purpose
CMTS01# ping docsis addr
Pings the cable modem with a specific MAC address or IP address to see if it is online.