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Chapter 2
Cisco CMTS Configuration Commands
cable spectrum-group hop threshold
To specify a frequency hop threshold for a spectrum group, use the cable spectrum-group hop
threshold command in global configuration mode. To delete the hop threshold for this spectrum group,
use the no form of this command.
Syntax Description
groupnum
percent
Defaults
20 percent
Command Modes
Global configuration
Command History
Release
12.1 T
12.1(7)CX1
12.2(4)BC1
12.2(15)BC2
Usage Guidelines
The Cisco CMTS sends a station maintenance message to each CM at least once every 25 to 30 seconds.
If a CM does not respond to a station maintenance message within that time period, the CMTS then
resends station maintenance messages at a faster rate (typically one second apart) in an attempt to restore
connectivity with the CM.
Station maintenance messages can be lost because CMs have lost connectivity with the CMTS, or
because ingress noise and other factors are causing dropped and errored packets. Downstream noise can
also affect the delivery of station maintenance messages. When a user-configurable percentage of station
maintenance messages are lost, the CMTS hops to a new upstream frequency to improve connectivity
and sends out an Upstream Channel Descriptor (UCD) update to the CMs to inform them of the change.
The optimal hop threshold value depends on several factors, including the quality of the upstream return
path and the number of CMs on the upstream. In addition, the hop threshold works together with the hop
period so that transient network problems do not generate an unnecessary number of frequency hops.
Ideally, the hop threshold should be set low enough so that the frequency hop can occur before a
significant number of CMs go offline, but not so low that it generates frequency hops that are not needed.
OL-1581-08
cable spectrum-group groupnum hop threshold [percent]
no cable spectrum-group groupnum hop threshold
Modification
This command was introduced.
The default hop threshold was changed from 100 percent to 20 percent to
accommodate the new spectrum management features for the Cisco uBR-
MC16S spectrum management card.
Support for this command was added to the Release 12.2 BC train.
The maximum number of spectrum groups was increased from 32 to 40
groups per router.
Spectrum group number. Valid values are from 1 to 32, or from 1 to 40,
depending on the Cisco IOS software release.
(Optional) Specifies the frequency hop threshold as a percentage of
station maintenance messages that are lost. Valid range is from 1 to 100
percent.
Cisco Broadband Cable Command Reference Guide
cable spectrum-group hop threshold
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