Installation guide

3-8
Cisco uBR7100 Series Universal Broadband Router Software Configuration Guide
OL-2238-03
Chapter 3 Configuring the Cisco Cable Interface
Configuring the Downstream Cable Interface
Perform these steps if you are having difficulty with verification:
1. Check the cables, upconverters, RF levels, and frequencies if the cable interfaces do not find a
downstream signal.
2. Check the cables, RF levels, and upstream frequencies, and enter a no shut command if the
cable interfaces find a downstream signal, but not an upstream signal.
3. Check the provisioning servers, ping the DHCP server using the source IP address option—the
primary IP address of a cable interface, check IP routing if the cable interfaces acquire an RF
upstream and downstream lock, but do not stay up.
4. Check DHCP options and the IP address of the TOD server, ping the TOD server using the source
IP address option, check IP routing, verify that the TFTP filename is correct, verify the TFTP file is
in the correct directory on the TFTP server, ensure the TFTP file has read privileges, ping the TFTP
server using the source IP address option, and check IP routing if the cable interfaces acquire an RF
and a DHCP, but fail on TOD or TFTP.
Setting Downstream Rate Limiting
Downstream rate limiting enables you to use the token bucket policing algorithm with traffic shaping
options or the weighted discard policing algorithm to buffer, shape, or discard packets that exceed a set
bandwidth. Downstream rate limiting is disabled by default.
To enable downstream rate limiting for a downstream port on a Cisco cable modem card, use one of the
following commands in cable interface configuration mode.
Command Purpose
CMTS01(config-if)# cable downstream
rate-limit token-bucket
CMTS01(config-if)# cable downstream
rate-limit token-bucket shaping
CMTS01(config-if)# cable downstream
rate-limit token-bucket shaping
granularity 8
CMTS01(config-if)# cable downstream
rate-limit token-bucket shaping max-delay
256
Enable rate limiting on the downstream port using the
token bucket policing algorithm. With this command,
the Cisco uBR7100 series router automatically drops
packets that are in violation of the allowable bandwidth.
Enable rate limiting on the downstream port using the
token bucket policing algorithm with traffic shaping.
Enable rate limiting on the downstream port using the
token bucket policing algorithm with specific traffic
shaping time granularity. Acceptable values are 1, 2, 4,
8, or 16 milliseconds.
Enable rate limiting on the downstream port using the
token bucket policing algorithm with specific maximum
traffic shaping buffering delay. Acceptable values are
128, 256, 512, or 1028 milliseconds.
CMTS01(config-if)# cable downstream
rate-limit weighted-discard 3
Enable rate limiting on the downstream port using the
weighted packet discard policing algorithm and assign a
weight for exponential moving average of loss rate.
Acceptable values are 1 to 4.
CMTS01(config-if)# ^Z
CMTS01#
Exit back to EXEC mode so that you can verify the
steps.