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Cisco uBR7200 Series Universal Broadband Router Software Configuration Guide

78-5897-01

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.

Verify Cable Modem Upstream Address Verification

To verify whether cable modem upstream verification is activated or deactivated, enter the command

more system:running-config and look for the no cable source-verify notation 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.

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

Command Purpose

CMTS01(config-if)# cable source-verify

[dhcp]

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

Activate cable modem upstream verification. The

dhcp option specifies that queries be sent to verify

unknown IP addresses in upstream data packets.

Return to the default upstream verification state.

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