Configuring Prbs Test Signals; Verifying Test Signal Output; Pinging Unresponsive Cable Modems; Pinging A Cable Modem - Cisco 7246VXR - uBR Router Software Configuration Manual

Pinging Unresponsive Cable Modems

Configuring PRBS Test Signals

Command
Step 1
Router(config-if)# cable downstream
if-output prbs
Step 2
Router(config-if)# no cable downstream
if-output

Verifying Test Signal Output

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 is shut down.
The functioning of the no cable downstream if-output command has not changed. The interface is shut
down.
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 uBR7200 series routers and the cable interface. The
technology uses 1/64—the bandwidth of IP ping—and works with CMs that do not have an IP address.
This allows cable operators to ping CMs that are unable to complete registration, that 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.
Command
Step 1
Router# ping docsis addr

Verifying the Ping

The ping docsis command returns a verification from a CM that is pinged:
Queuing 5 MAC-layer station maintenance intervals, timeout is 25 msec:
!!!!!
Success rate is 100 percent (5/5)
Cisco uBR7200 Series Universal Broadband Router Software Configuration Guide
8-10
Purpose
Generates a PRBS test signal on the downstream channel. The
interface is shut down.
Stops sending test signals.
Remember to reenable the interface to resume normal
Note
operations.
Purpose
Pings the CM with a specific MAC address or IP address to see if it is online.
Chapter 8 Troubleshooting the System
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