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Cisco uBR7200 Series Universal Broadband Router Software Configuration Guide
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Chapter4 Troubleshooting the System Managing Cable Modems on the HFC Network

Verify Sync Message Interval

To verify whether or not a sync message interval is configured, enter the showrunning-config
command and look for the cable interface configuration information. If the sync message interval is
deactivatedor reset to its default value, the no sync interval command line appears in the output.
Activate Cable Modem Authentication
TheCisco uBR7200 series can be configured to require all cable modems to return a known text string
toregister with the CMTS and gain access to the network. The text string can be from 1 to 80 characters
in length. To activate cable modem authentication, use the following command from cable interface
configuration mode.
Tips Be sure you enter the correct slot and port number in the cable interface configuration
mode. Verify that the cablemodem is using BPI and that it is assigned to a QoS with
privacy active. Verify that the cablemodem configuration file contains a matching key.

Verify Cable Modem Authentication

To verify whether cable modem authentication is activated or deactivated, enter the command more
system:running-config and look for the cable interface configuration information. If cable modem
authentication is deactivated, it appears in this output as no cable secret-shared.
Activate Cable Modem Upstream Address Verification
Cablemodem upstreamaddress verificationensures that only cable modems that have received DHCP
leases through the Cisco uBR7200 series can access the HFC network. The Cisco uBR7200 series
discards all packets received from or for hosts that have not received DHCP-assigned addresses.
Table4-2 Instructions to Activate Cable Modem Authentication
Command Purpose
CMTS01(config-if)# cable shared-secret
[0|7]
authorization-key
CMTS01(config-if)#no cable shared-secret
Enable cable modem authentication: 0 specifies an
unencrypted authentication key;7 specifies an
encrypted authentication key.
Disable cable modem authentication.