Cisco Systems uBR7200 manual Setting Upstream Backoff Values, Verifying the Upstream Ports, MC-559

Configuring Headend Broadband Access Router Features

Configuring the Upstream Cable Interface

To activate the upstream ports, use the following commands beginning in global configuration mode:

	Command	Purpose
Step 1
	CMTS01(config)# interface cable slot/port	Specifies a cable interface and enters cable interface
		configuration mode.
Step 2
	CMTS01(config-if)#no cable upstream usport shutdown	Enables upstream data traffic.

Verifying the Upstream Ports

To verify whether the upstream ports are activated or deactivated, enter the show interface cable command for the upstream port that you have just configured:

router# show interface cable 6/0 Cable6/0 is up, line protocol is up

Hardware is BCM3210 FPGA, address is 00e0.1e5f.7a60 (bia 00e0.1e5f.7a60) Internet address is 1.1.1.3/24

MTU 1500 bytes, BW 27000 Kbit, DLY 1000 usec, rely 255/255, load 1/255 Encapsulation, loopback not set, keepalive not set

ARP type: ARPA, ARP Timeout 04:00:00

Last input 00:00:25, output 00:00:00, output hang never Last clearing of “show interface” counters never Queueing strategy: fifo

Output queue 0/40, 0 drops; input queue 0/75, 0 drops

Troubleshooting Tips

To troubleshoot the configuration, perform the following tasks:

•Make sure the cable connections are not loose or disconnected.

•Make sure the Cisco cable modem card is firmly seated in its chassis slot and the captive installation screws are tight.

•Make sure you entered the correct slot and port numbers when you typed the command.

•Make sure you entered the correct upstream port number:

–On the MC16C cable modem card, this can be u0 to u5.

–On the MC14C cable modem card, this can be u0 to u3.

–On the MC12C cable modem card, this can be u0 or u1.

–On the MC11C cable modem card, this can be u0 only.

Setting Upstream Backoff Values

The DOCSIS-specified method of contention resolution for cable modems wishing to transmit data or requests on the upstream channel is a truncated binary exponential backoff, with the initial backoff window and the maximum backoff window controlled by the CMTS. The Cisco uBR7200 series router specifies backoff window values for both data and initial ranging, and sends these values downstream as part of the Bandwidth Allocation Map (MAP) MAC message. The values are configurable on the Cisco uBR7200 series and are power-of-two values. For example, a value of 4 indicates a window from 0 to 15; a value of 10 indicates a window from 0 to 1023.

Cisco IOS Multiservice Applications Configuration Guide

MC-559