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Cisco uBR7200 Series Universal Broadband Router Software Configuration Guide
OL-2239-03
Chapter 3 Configuring Cable Modem Interface Features
Configuring the Downstream Cable Modem Interface
Note
The
cable downstream channel-id
command must be used with the following command:
cable downstream frequency 54000000-1000000000 broadcast frequency - h
These commands are used in instances where you want to send multiple downstream frequencies to a
single region that contains CMs that can connect only to upstream ports on the same cable interface line
card. You must configure unique channel IDs for each downstream that any CM is capable of receiving.
The downstream frequency setting must match the setting on the upconverter.
Caution
After defining unique downstream IDs, test the CMs for correct operation. Cisco recommends that when
using this feature, you re-test each subsequent software release of CM code to verify correct operation
and to ensure reasonable acquisition time for new installations. Failure to use these commands in
conjunction or to test the involved CMs can result in customer service outages of indefinite duration.
Verifying the Downstream Channel ID
To verify the downstream channel ID, enter the
show controllers cable
command for the downstream
port you have just configured. See the following example:
Router#
show controllers cable5/0 downstream
Cable5/0 Downstream is up
Frequency=96000000, Channel Width 6 MHz, 64-QAM, Symbol Rate 5.056941 Msps
FEC ITU-T J.83 Annex B, R/S Interleave I=32, J=4
Downstream channel ID: 1
Configuring Downstream Rate Limiting and Traffic Shaping
To configure downstream traffic shaping, use the following command in cable interface configuration
mode.
Note
Using Cisco IOS Release 12.0(5)T1 or higher, the software adds downstream calendar queuing routines
and grant shaping application of the calendar queues.
Details for key command usage are provided below:
•
To enable rate limiting on the given downstream port using the token bucket policing algorithm,
issue the
cable downstream rate-limit token-bucket
command.
•
To enable rate limiting on the given downstream port using the token bucket policing algorithm with
traffic shaping, issue the
cable downstream rate-limit token-bucket shaping
command.
•
To enable rate limiting on the given downstream port using the token bucket policing algorithm with
a specific traffic shaping time granularity, issue the
cable downstream rate-limit token-bucket
shaping granularity 8
command. Acceptable values are 1, 2, 4, 8, or 16 msecs.
•
To enable rate limiting on the given downstream port using the token bucket policing algorithm with
a specific maximum traffic shaping buffering delay, issue the
cable downstream rate-limit
token-bucket shaping granularity 8
command. Acceptable values are 128, 256, 512, or 1028 msecs.
Command
Purpose
Router(config-if)#
[no]
cable downstream rate-limit
token-bucket
[shaping]
weighted-discard
[expwt <n>]
Enables or disables rate limiting and
traffic shaping on the downstream of a
cable interface.
