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Cisco uBR7200 Series Universal Broadband Router Software Configuration Guide
OL-2239-03
Chapter 5 Managing Cable Modems on the Hybrid Fiber-Coaxial Network
Activating Cable Modem Authentication
Note Cisco recommends using default values for most commands. The default values for the commands used
in these configuration steps are, in most cases, adequate to configure the Cisco uBR7200 series.
For information about setting rate limiting on CMs, refer to these sections in Chapter 3:
• “Setting Downstream Traffic Shaping” section on page 3-10
• “Setting Upstream Traffic Shaping” section on page 3-26
Activating Cable Modem Authentication
The Cisco uBR7200 series router can be configured to require all CMs to return a known text string to
register with the CMTS and gain access to the network. The text string can be from 1 to 80 characters in
length. The default setting is "on" (CM authentication is activated).
To activate CM authentication, use the following command in cable interface configuration mode:
Tip Ensure that you enter the correct slot and port number, and verify that the cable interface configuration
file contains a matching key.
Note The Cisco uBR7200 series router will accept any DOCSIS configuration file with any shared secret if
the CMTS configuration does not contain a setting for shared secret. However, if the CMTS
configuration contains a setting for shared secret, the settings between the DOCSIS configuration file
and the CMTS configuration must match. The shared secret for the CMTS configuration must be entered
again or the file will no longer contain the correct MD-5 MIC setting, and CMs will stop working,
registering in state reject(m).
Verifying CM Authentication
To verify if CM authentication has been activated or deactivated, enter the more system:running-config
command and look for the cable interface configuration information. If CM authentication has been activated,
it does not appear in this output. If CM authentication has been deactivated, it appears in this output as “
no
cable secret-shared
,” as shown in this sample command output:
Router# more system:running-config
Building configuration...
Current configuration:
!
interface Cable5/0
ip address 1.1.1.1 255.255.255.0
no keepalive
Command Purpose
cable shared-secret [0|7] authorization-key
no cable shared-secret
Enables CM authentication:
• 0 specifies an unencrypted authentication key.
• 7 specifies an encrypted authentication key.
Disables CM authentication.
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