Assigning The Downstream Channel Id; Setting The Downstream Helper Address - Cisco uBR10012 Software Configuration Manual

Chapter 3 Configuring Cable Interface Features for the Cisco uBR10012 Router

Assigning the Downstream Channel ID

To assign a numeric channel ID to the downstream port on the Cisco cable interface line card, use the
following command in cable interface configuration mode. The acceptable range is 0 to 255.
Router(config-if)# cable downstream channel-id id
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 cable5/0/0 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: 1

Setting the Downstream Helper Address

Specify an IP address of a Dynamic Host Configuration Protocol (DHCP) server where User Datagram
Protocol (UDP) broadcast packets will be sent. You can specify a DHCP server for UDP broadcast
packets from cable interfaces, and a DHCP server for UDP broadcast packets from hosts. To set a
downstream helper address, use the following commands in cable interface configuration mode.
Command
Step 1
Router(config-if)# cable
helper-address 10.x.x.x
cable-modem
Step 2
Router(config-if)# cable
helper-address 172.56.x.x host
OL-1520-05
Purpose
Set the downstream helper address to the DHCP server at IP
address 10.x.x.x for UDP broadcast packets from cable modems.
Note Use the IP address of the DHCP server. Both 10.x.x.x and
172.56.x.x are private ranges.
Set the downstream helper address to the DHCP server at IP
address 172.56.x.x for UDP broadcast packets from hosts.
Cisco uBR10012 Universal Broadband Router Software Configuration Guide
Configuring the Downstream Cable Interface
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