user manual

Configuring Headend Broadband Access Router Features
Configuring the Downstream Cable Interface
MC-535
Cisco IOS Multiservice Applications Configuration Guide
Configuring the Downstream Cable Interface
The first step in configuring the Cisco cable modem interface is to configure the downstream cable
interface. The downstream direction refers to the data flow from the Cisco cable modem card in a
Cisco uBR7200 series to the subscriber’s cable modem. Data passing through the Cisco cable modem
card is converted to IF and then passed through an upconverter to transform the signal to RF. This RF
signal is then sent down the line to the subscriber’s cable modem. Downstream cable interface
commands configure the frequency, symbol rate, compression, and modulation of the downstream
signal.
To configure the downstream cable interface, perform the following tasks:
• Activating the Downstream Carrier
• Setting the Downstream Center Frequency
• Setting the Downstream Channel ID
• Setting the Downstream MPEG Framing Format (Annex B)
• Setting the Downstream Modulation
• Setting the Downstream Interleave Depth
• Setting the Downstream Helper Address
• Setting Downstream Rate Limiting
Note In most applications, the default values for the commands used in these configuration steps
are adequate to configure the Cisco uBR7200 series router.
Activating the Downstream Carrier
To activate a downstream port on a Cisco uBR7200 series cable modem card for digital data
transmissions over the HFC network, use the following commands:
Command Purpose
Step 1
CMTS01> enable
Password: <password>
CMTS01#
Enters enable (privileged EXEC) mode.
Enters the password.
You have entered privileged EXEC mode when the
prompt displays the pound symbol (
#).
Step 2
CMTS01# configure terminal
Enter configuration commands, one per line. End with
CNTL/Z.
CMTS01(config)#
Enters global configuration mode. You have entered
global configuration mode when the prompt displays
(config)#.
This command can be abbreviated to config t.
Step 3
CMTS01(config)# interface cable 6/0
CMTS01(config-if)#
Enters cable interface configuration mode.
In this example, the interface is downstream port 0 on
the cable modem card installed in slot 6 of the
Cisco uBR7200 series.