Configuring Headend Broadband Access Router Features
Configuring the Downstream Cable Interface
MC-542
Cisco IOS Multiservice Applications Configuration Guide
• If the cable modems acquire an RF and a DHCP, but fail on TOD or TFTP: check DHCP options and
the IP address of the TOD server; ping the TOD server using the source IP address option (the
primary IP address of a cable interface); check IP routing; verify that the TFTP filename is correct,
the TFTP file is in the correct directory on the TFTP server, and that the TFTP file has read
privileges for all; ping the TFTP server using the source IP address option (the primary IP address
of a cable interface); check IP routing, and so on.
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
Step 1
CMTS01(config-if)# cable downstream rate-limit
token-bucket
or
CMTS01(config-if)# cable downstream rate-limit
token-bucket shaping
or
CMTS01(config-if)# cable downstream rate-limit
token-bucket shaping granularity 8
or
CMTS01(config-if)# cable downstream rate-limit
token-bucket shaping max-delay 256
Enables rate limiting on the downstream port using
the token bucket policing algorithm. With this
command, the Cisco uBR7200 series will
automatically drop packets in violation of the
allowable bandwidth.
Enables rate limiting on the downstream port using
the token bucket policing algorithm with traffic
shaping.
Enables 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 (ms).
Enables 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 ms.
Step 2
CMTS01(config-if)# cable downstream rate-limit
weighted-discard 3
Enables 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.
Step 3
CMTS01(config-if)# ^ZCMTS01#
Exits to EXEC mode so that you can verify the steps.
