Installation guide

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Cisco uBR7100 Series Universal Broadband Router Software Configuration Guide
OL-2238-03
Chapter 3 Configuring the Cisco Cable Interface
Configuring the Upstream Cable Interface
Note Software adjustments of 1 to 3 dB can be used to adjust for minor variations in measurement or setup
and port-to-port calibration differences. These adjustments can significantly improve cable interface
performance, especially in marginal situations. Larger adjustments should be made in conjunction with
spectrum analyzer-support at the headend or distribution hub.
Activating Upstream Admission Control
The admission control is set as a percentage of the specified upstream channel capacity. The acceptable
range is from 10 to 1000 percent. Admission control is disabled by default.
To set the upstream admission control as a percentage of the upstream channel capacity, use the
following command in cable interface configuration mode. Valid range is from 10 to 1000 percent.
CMTS01(config-if)# cable upstream usport admission-control percentage
Verifying Upstream Admission Control
To determine if upstream admission control is configured and activated, enter the show running-config
command in privileged EXEC mode and look for the cable interface configuration information. If
upstream admission control is configured and enabled, an admission control entry displays in the
show running-config output, indicating the user-defined percentage of upstream channel capacity
allowable. If upstream admission control is disabled, no admission control entry displays in the output.
Perform these steps if you are having difficulty with verification:
1. Ensure the cable connections are not loose or disconnected
2. Ensure the cable modem card is firmly seated in its chassis slot.
3. Ensure the captive installation screws are tight.
4. Verify that you have entered the correct slot and port numbers.
5. Verify that you selected a valid frequency for your router.
Activating Upstream Forward Error Correction (FEC)
The Cisco uBR7100 series CMTS uses forward error correction (FEC) to attempt to correct any
upstream data that might have been corrupted. FEC is activated by default and should not be disabled.
When FEC is activated, all cable modems on the network also activate FEC.
Note Although upstream FEC is an option, Cisco recommends that you use upstream FEC.
To activate the upstream forward error correction and to enable FEC, use the following command in
cable interface configuration mode. FEC is enabled by default.
CMTS01(config-if)# cable upstream usport fec