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Cisco uBR10012 Universal Broadband Router Software Configuration Guide
OL-1520-05
Chapter3 Configuring Cable Interface Features for the CiscouBR10012Router Configuring the Downstream Cable Interface
Step1 Ensure that the cable connections are not loose or disconnected.
Step2 Ensure that the cable interface line card is firmly seated in its chassis slot.
Step3 Ensure that the captive installation screws are tight.
Step4 Verify that you have entered the correct slot and port numbers
Step5 Verify that the downstream carrier is active, using the cable downstream if-output command
Step6 Verify that you have selected the default if you are not certain about the modulation rate needed.
Setting the Downstream MPEG Framing Format
The MPEG framing format must be compatible with DOCSIS specifications (viewable at
http://www.cablemodem.com/specifications.html) and your local cable plant operations.
Tip AnnexB is the DOCSIS MPEG framing format standard for North America.
Note Annex B framing format is automatically set when configuring Cisco cable interface line cards. The
cable interface line card’s downstream ports and the connected CMs on the network must be set to
the same MPEG framing format and must support DOCSIS operations as appropriate.
The following command appears in the CiscouBR10012router configuration file to designate AnnexB
operation. This command sets the downstream MPEG framing format.
Router(config-if)# cable downstream annex {B}

Verifying the Downstream MPEG Framing Format

To verify the downstream MPEG framing format setting, enter the show controllers cable command for
the downstream port you have just configured. See the following example:
router# show controllers cable5/0/0 downstream
Cable5/0/0 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: 0
Setting Downstream Rate Limiting and Traffic Shaping
Downstream traffic shaping enables you to use the token bucket policing algorithm with traffic shaping
options or the weighted discard algorithm to buffer, shape, or discard packets that exceed a set
bandwidth. Downstream traffic shaping is disabled by default.
To enable downstream traffic shaping for a downstream port on a Cisco cable interface line card, use one
of the following commands in cable interface configuration mode.