3-22
Cisco uBR10012 Universal Broadband Router Software Configuration Guide
OL-1520-05
Chapter 3 Configuring Cable Interface Features for the Cisco uBR10012 Router
Configuring the Upstream Cable Interface
Note
The upstream cable interface does not operate until you either set a fixed upstream frequency or
create and configure a spectrum group.
If you are setting a fixed upstream frequency, make sure that the frequency selected does not interfere
with the frequencies used for any other upstream applications running on the cable plant.
To set a fixed upstream frequency, use the following commands in cable interface configuration mode.
Tip
For National Television Standards Committee (NTSC) operations, valid ranges are 5000000 to
42000000 Hz.
Caution
Some cable systems cannot reliably transport frequencies near these band edges. The wider the
upstream channel (in MHz), the more difficulty you might have. Enter a center frequency between
20 and 38 MHz if you have difficulty.
Note
You can also select a default that does not set a specific fixed value. The Cisco uBR10000 series
software instructs the cable interfaces to use this frequency as the center frequency.
Verifying the Upstream Frequency
To verify the current value of the upstream frequency, enter the
show controllers cable
command for
the upstream port you have just configured:
Router#
show controllers cable5/0/0 u0
Cable5/0/0 Upstream 0 is up
Frequency 24.016 MHz, Channel Width 1.600 MHz, QPSK Symbol Rate 1.280 Msps
Spectrum Group is overridden
SNR 33.2560 dB
Nominal Input Power Level 0 dBmV, Tx Timing Offset 2288
Ranging Backoff automatic (Start 0, End 3)
Ranging Insertion Interval automatic (60 ms)
Tx Backoff Start 0, Tx Backoff End 4
Modulation Profile Group 1
Note
The upstream frequency displayed in the
show controllers cable
command output might not match
the frequency that you entered when you set the upstream frequency. The Cisco uBR10000 series
CMTS might select an upstream frequency close to the frequency you entered that offers better
performance. The Cisco uBR10000 series CMTS selects the closest frequency available.
Perform these steps if you are having difficulty with verification:
Command
Purpose
Step 1
Router(config-if)#
cable upstream
usport
frequency
up-freq-hz
Enters the fixed center frequency for your upstream
RF carrier in Hz.
Step 2
Router(config-if)#
no cable upstream
usport
shutdown
Places the upstream port in the “admin up” state.