Cisco Systems uBR7200 Series manual Verify Cable Modem Upstream Address Verification

Chapter 4 Troubleshooting the System

Managing Cable Modems on the HFC Network

To activate cable modem upstream address verification, use the following cable interface configuration command.

Table 4-3 Instructions to Activate Cable Modem Upstream Address Verification

Command	Purpose
CMTS01(config-if)#cable source-verify [dhcp]	Activate cable modem upstream verification. The
	dhcp option specifies that queries be sent to verify
	unknown IP addresses in upstream data packets.

CMTS01(config-if)#no cable source-verify

Return to the default upstream verification state.

Verify Cable Modem Upstream Address Verification

To verify whether cable modem upstream verification is activated or deactivated, enter the command more system:running-configand look for the no cable source-verifynotation in the cable interface configuration information.

Tips Be sure you enter the correct slot and port number when you enter the cable interface configuration mode.

Note If the Cisco uBR7200 series is reloaded or the ARP table is cleared, all hosts on the network will be forced to release and renew their IP addresses. Some systems may require restarting if the IP protocol stack is unable to renew using a broadcast IP address.

Configure Dynamic Contention Algorithms (Cable Insertion Interval, Range, and Data Backoffs)

The Cisco uBR7200 series universal broadband router software includes:

•An algorithm that dynamically controls the rate of upstream contention slots —initial ranging and bandwidth-requests.

•An algorithm that varies backoff parameters CMs use within each of the initial ranging and bandwidth-request upstream contention subchannels.

These algorithms control the capacity of the contention subchannel and how efficiently a given contention subchannel capacity is utilized.

In high contention mode, the Cisco uBR7200 series MAC scheduler uses collision statistics and sustains a high frequency of initial ranging slots until it detects a steady ranging state. The CMTS dynamically varies the frequency of initial ranging slots using the data grant utilization on the upstream channel(s). The CMTS trades upstream bandwidth between data grants and initial ranging slots. The CMTS auto-detects a high collision state and switches to low insertion interval mode after a steady state is achieved where few collisions occur.

The CMTS is careful when monitoring the ranging channel health to revert to a steady state. In steady state mode, data grants—grant utilization—receive preference over initial ranging slots.

Cisco uBR7200 Series Universal Broadband Router Software Configuration Guide

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