Installation guide
3-7
Cisco uBR7100 Series Universal Broadband Router Software Configuration Guide
OL-2238-03
Chapter 3 Configuring the Cisco Cable Interface
Configuring the Downstream Cable Interface
Verifying the Downstream Interleave Depth
To verify the downstream interleave depth setting, enter the show controllers cable command for the
downstream port you have just configured:
Router# show controllers cable1/0 downstream
Cable1/0 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
Perform these steps if you are having difficulty with verification:
1. Ensure the cable connections are not loose or disconnected.
2. Ensure the cable modem card is firmly seated in its chassis slot.
3. Ensure the captive installation screws are tight.
4. Verify that you have entered the correct slot and port numbers.
5. Verify that the downstream carrier is active using the cable downstream if-output command.
Setting the Downstream Helper Address
Specify an IP address of a DHCP server where UDP broadcast (DHCP) 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.
Verifying the Downstream Helper Address
To verify the downstream helper address setting, enter the show running-config command and look for
cable helper-address in the cable interface configuration information:
CMTS01# show running-config
Building configuration...
Current configuration:
!
interface Cable1/0
ip address 10.254.254.254 255.0.0.0
no ip directed-broadcast
cable helper-address 192.168.1.1
no keepalive
Command Purpose
Step 1
CMTS01(config-if)# cable
helper-address 10.x.x.x cable-modem
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.
Step 2
CMTS01(config-if)# cable
helper-address 172.56.x.x host
Set the downstream helper address to the DHCP server at IP address
172.56.x.x for UDP broadcast packets from hosts.