user manual

Configuring Headend Broadband Access Router Features
Configuring the Upstream Cable Interface
MC-555
Cisco IOS Multiservice Applications Configuration Guide
Step 4 Make the cable modem exceed its peak upstream rate by generating heavy upstream traffic and see the
effect of grant buffering (shaping) at the CMTS. If you use cable modem-to-CMTS pings, you will notice
the pings slowing down.
Let the pings run for a few minutes (to let averages at CMTS settle); then see the upstream rate received
by this single modem. Use the show interface cx/y command and observe the input rate in bps. This
value should be close to the modem’s peak upstream rate. Also observe the drop counts for the modem’s
SID by using the show interface sid counters command and see that CMTS no longer drops the
bandwidth requests from the cable modem.
The bandwidth request drop count (from previous nonshaping test) remains unchanged when upstream
rate shaping is used, indicating that the CMTS is actually shaping (buffering) the grants for the modem.
See that the input rate at the CMTS (from the single rate-exceeded cable modem) stabilizes close to the
configured peak rate of 128 kbps.
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.
Activating Upstream Frequency Adjustment
To enable automatic upstream frequency adjustment for a specified cable interface, use the following
command in cable interface configuration mode:
To return the automatic upstream frequency adjustment percentage to the default value of 30 percent,
enter the following command in cable interface configuration mode:
CMTS01(config-if)# no cable upstream usport frequency-adjust averaging
Command Purpose
CMTS01(config-if)# cable upstream usport
frequency-adjust averaging percentage
Sets the minimum number of frequency adjustment packets
required to justify changing the upstream frequency
adjustment method as a percentage. Acceptable range is
10 to 100 percent. Default = 30 percent.