CHAPTER

4-1
Cisco uBR7200 Series Universal Broadband Router Software Configuration Guide
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4
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 universal broadband 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 Afterthe Cisco uBR924 is operational and you have an input signal between 0 and +5 dBmV, enter the
show controller c0 tuner command.
Step 2 Scanthe 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.