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Cisco uBR7200 Series Universal Broadband Router Software Configuration Guide
OL-2239-03
Chapter8 Troubleshooting the System
Using a Headend Cable Modem to Verify Downstream Signals
Using a Headend Cable Modem to Verify Downstream Signals
You can use a Cisco uBR924 cable access modem to verify the downstream signal originating from a
CiscouBR7200series router. Be sure that you configure the CiscouBR924 according to DOCSIS CM
practices.
To verify the downstream signal from a CiscouBR7200series router using a CiscouBR924, follow the
procedure below:
Step1 After the CiscouBR924 is operational and you have an input signal between 0 and +5 dBmV, use the
show controller c0 tuner command.
Step2 Scan the output for the value corresponding to the signal-to-noise (SNR) estimate variable. If this value
is at least 35dB, you have an optimized signal. If the value is less than 34dB, adjust the upconverter at
the cable headend.
Tip The SNR estimate for a CM installed at a headend should be between 35 and 39dB. Although the exact
value displayed varies from CM to CM, values collected on the same CM from measurement to
measurement will be consistent. Maximizing SNR optimizes CM reliability and service quality.
show interface cable
sid
To display the service identifier (SID) for a CM, use the
showinterfacecablesid command in privileged EXEC mode.
The following sample output from the show interface cable sid command
shows the one form of the command:
Router# show int c4/0 sid
Sid Prim MAC Address IP Address Type Age Admin Sched Sfid
State Type
5 0010.7b6b.58c1 10.20.114.34 stat 2d1h36menable BE 1
6 0010.7bed.9dc9 10.20.114.37 stat 2d1h36menable BE 13
7 0010.7bed.9dbb 10.20.114.38 stat 2d1h36menable BE 15
8 0010.7b6b.58bb 10.20.114.112 stat 2d1h34menable BE 17
9 0010.7b6b.58bb 10.20.114.112 dyna 2d1h34menable BE 19
show cable
modulation-profile
To display modulation profile group information for a Cisco CMTS, use the
show cable modulation-profile command in privileged EXEC mode.
The showcablemodulation-profile command now includes an added option
number that displays the modulation profile number.
The show cable modulation-profile command completely replaces the former
showcableburst-profile command.
Command Purpose