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Cisco Broadband Cable Command Reference Guide
OL-1581-08
Chapter 2 Cisco CMTS Configuration Commands
cable upstream channel-width
Command History
Usage Guidelines The last-choice-width parameter is supported only by the Cisco uBR-MC16S, Cisco uBR-MC16U/X,
Cisco uBR-MC28U/X, and Cisco uBR-MC5X20S/U cable interface line cards. When one of these
particular cards is installed, the system attempts to increase the channel width from the smallest channel
width value to the largest channel width value, one step at a time.
Note
In Cisco IOS Release 12.2(15)BC1 and later releases, changing the channel width could also force a
frequency hop, if the current frequency does not fit within the new channel width parameters, or if the
system needs to reset the fixed frequency or shared frequency group parameters to match the new
channel width.
Caution
In DOCSIS 1.X networks, do not change the channel width more than one step at a time on an interface
that has cable modems that are currently online. The DOCSIS 1.X specifications require that cable
modems remain online when the channel width is changed in single step increments (such as 800,000 to
1,600,000), but cable modems can go offline when you change the channel width in larger amounts (such
as changing it from 800,000 to 3,200,000). DOCSIS 2.0 cable modems might support changing the
channel width by two steps, but each brand of modem should be tested for this before attempting it on a
live network. Also, after changing the channel width, do not change the channel width again until all
cable modems have performed their ranging adjustments for the new width (which could take up to a
minute, depending on the number of cable modems).
Note
To specify only one channel width for the Cisco uBR-MC16S, Cisco uBR-MC16U/X,
Cisco uBR-MC28U/X, or Cisco uBR-MC5X20S/U card, specify the same value for both the
first-
choice-width and last-choice-width parameters. For example:
cable upstream 0 channel-width 800000 800000
When using this command to change channel-widths for an upstream interface on the
Cisco uBR-MC5X20S cable interface line card, some DOCSIS 1.1 CMs can go offline if you do not also
change the minislot size to the corresponding value. See the following examples for the correct channel-
width and minislot pairings:
router(config-if)# cable upstream 0 channel-width 3200000
router(config-if)# cable upstream 0 minislot 4
Release Modification
11.3(5)NA This command was introduced.
12.0(4)XI The last-choice-width argument was added.
12.2(11)CY,
12.2(11)BC3 Support was added for the Cisco uBR10-MC5X20S cable interface line card
on the Cisco uBR10012 router.
12.2(15)CX Support was added for the Cisco uBR-MC16U/X and Cisco uBR-MC28U/X
cable interface line card, including DOCSIS 2.0 A-TDMA and mixed
modulation profiles using 6.4 MHz channel widths.
12.2(15)BC2 Support was added for DOCSIS 2.0 A-TDMA and mixed modulation
profiles using 6.4 MHz channel widths on the Cisco uBR-MC5X20S/U cable
interface line cards.