Cisco Systems MC-607 manual Customizing the Cable Access Router Interface, MC-649

Configuring Subscriber-End Broadband Access Router Features

Customizing the Cable Access Router Interface

Customizing the Cable Access Router Interface

Different geographical regions and different cable plants use different frequency bands. The

Cisco uBR900 series cable access router uses a built-in default frequency scanning feature to address this issue. After the cable access router finds a successful downstream frequency channel, it saves the channel and power setting to NVRAM. The cable access router recalls this value the next time it needs to synchronize its frequency or register with the cable service provider CMTS.

However, you can customize the cable access router interface configuration if you need to deviate from the default setting that ships with the unit. For example, you might need to specify a different compliant mode, modify the saved downstream channel setting and upstream power value, or enable a faster downstream search algorithm.

Note Most cable network scenarios will not require you to use the commands in this section.

To customize the cable access router interface, use the following commands beginning in global configuration mode:

	Command	Purpose
Step 1
	uBR924(config)# interface cable-modem 0	Specifies cable access router interface 0.
Step 2
	uBR924(config-if)#cable-modem compliant bridge	Enables DOCSIS-compliant bridging.
Step 3
	uBR924(config-if)#cable-modem downstream saved	Modifies the saved downstream channel setting and
	channel ds-frequency us-power	upstream power value. If you do this, you must
		specify an exact downstream frequency and a power
		value.1
Step 4	uBR924(config-if)#cable-modem fast-search	Enables a faster downstream search algorithm.

1. Use the no cable-modem downstream saved channel ds-frequencyus-powercommand to remove a saved frequency and power setting from

NVRAM.

Using Multiple PCs with the Cable Access Router

The MAX CPE parameter in the DOCSIS configuration file determines how many PCs or other CPE devices are supported by a particular cable access router. The default value for the MAX CPE parameter is 1, which means only one PC can be connected to the cable access router unless this value is changed.

The DOCSIS 1.0 specification states that a CMTS cannot age out MAC addresses for CPE devices. Thus, if MAX CPE = 1, the first PC that is connected to a cable access router is normally the only one that the CMTS recognizes as valid. If you wish to replace an existing PC or change its network interface card (NIC) to one that has a different MAC address, the CMTS will refuse to let the PC come online because this would exceed the maximum number of CPE devices specified by the MAX CPE parameter.

If you wish to replace an existing PC or NIC, use one of the following workarounds:

•Use the clear cable host reset command on the Cisco uBR7200 series universal broadband router to remove the PC MAC address from the router internal address tables. The PC MAC address will be rediscovered and associated with the correct cable access router during the next DHCP lease cycle.

Cisco IOS Multiservice Applications Configuration Guide

MC-649