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Set the Downstream MPEG Framing Format (Annex A or Annex B)
Configuring Cisco uBR7246 Universal Broadband Router Features VC-141
Set the Downstream MPEG Framing Format (Annex A or Annex B)
The MPEG framing format must be compatible with the downstream symbol rate you set. Set the
MPEG framing format for a downstream port on a cable modem card to either Annex A or Annex B.
Annex B is the North America standard and Annex A is the European standard. You should review
your local standards and specifications for downstream MPEG framing to determine which format
you should use.
Note The cable modem card downstream ports and the cable modems on the HFC network
connected through these ports must be set to the same MPEG framing format.
To set the downstream MPEG framing format, use the following command in cable interface
configuration mode:
Validation Tips
To verify the downstream MPEG framing format (Annex A or Annex B) setting, enter the show
controllers cable command for the downstream port that you have just configured:
router# show controllers cable 6/0 downstream
Cable6/0 Downstream is up
Frequency=96000000, Channel Width 6 MHz, 64-QAM, Symbol Rate 5.056941 Msps
FEC ITU-T J.83 Annex B, R/S Interleave I=32, J=4
Troubleshooting Tips
If you are having trouble:
• Make sure the cable connections are not loose or disconnected.
• Make sure the cable modem card is firmly seated in its Cisco uBR7246 chassis slot.
• Make sure that you have entered the correct slot and port numbers when you typed the command.
• Make sure you have selected the correct setting for your location.
• Make sure the downstream carrier is active by entering the cable downstream if-output
command.
Set the Downstream Modulation
Downstream modulation is the number of symbols per second; by setting the downstream
modulation, you define the speed at which data travels downstream to the user, which is 64 qam
(6 bits per downstream symbol rate).
Note The Cisco cable modem cards currently do not offer a downstream modulation setting for
256-QAM (8 bits per downstream symbol rate).
Command Purpose
cable downstream annex {A | B} Set the downstream MPEG framing format.