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Cisco uBR7200 Series Universal Broadband Router Software Configuration Guide
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Chapter4 Troubleshooting the System
Managing Cable Modems on the HFC Network
Caution Only a trained CMTS administrator should adjust these values.
To configure the dynamic map advance algorithm, use the following command in cable interface
configuration mode.
Caution Cisco recommends if you are adjusting the dynamic map advance algorithm that you do
notreduce the safety factor below the default value of 1000 usecs in a production network
until you are confident that the reduced safety factor suffices for your deployment. The
default value is chosen to be a safe operating point for the algorithm.
Configure Per Modem Filters
You can configure the CiscouBR7200 series to filter incoming packets from individual hosts or
cable modems based on the source Media Access Controller (MAC)or Internet Protocol (IP) address.
Definition of filters follows standard Cisco IOS configuration practices for access lists and groups.
Note Configuring per modem or host filters is supported in Cisco IOS Release 12.0(5)T1 or
higher, as well as in CiscoIOS Release 12.0(6)SC or higher.
Table4-5 Instructions to Configure the Dynamic Map Advance Algorithm
Command Purpose
CMTS01(config-if)#cable map-advance dynamic
[<n>]
| static Specify a value to enhance the upstream
throughput from a cable modem connected to the
Cisco uBR7200 series. The <n> parameter
provides the safety factor for the dynamic map
advance algorithm. This parameter is specified in
usecs and controls the amount of extra lookahead
time in MAPs to account for inaccuracies of the
measurement system and software latencies. The
default value is 1000 usecs.
Youcan vary this between 500 to 1500 usecs.This
parameter is a delta value added to the dynamic
map-advance that the algorithm computes. Using
larger safety factors increases the run time
lookahead in MAPs, but reduces the upstream
performance.
Use the statickeyword for the map advance
command. The Cisco uBR7200 series will use a
fixed lookahead time in MAPs, regardless of the
realpropagation delay of the farthest cable modem
on the network. This fixed lookahead time is
computedbased on the worst case parameters such
as farthest DOCSIS propagation delay for the
CMs.