Installation guide

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Cisco uBR7100 Series Universal Broadband Router Software Configuration Guide
OL-2238-03
Chapter 3 Configuring the Cisco Cable Interface
Configuring the Upstream Cable Interface
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 uBR7100 series software
commands 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:
CMTS01# show controllers cable1/0 u0
Cable1/0 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 uBR7100 series CMTS
might select an upstream frequency close to the frequency you entered that offers better performance.
The Cisco uBR7100 series CMTS selects the closest frequency available.
Perform these steps if you are having difficulty with verification:
1. Ensure the cable connections are not loose or disconnected
2. Ensure the cable modem card is firmly seated in its chassis slot.
3. Ensure the captive installation screws are tight.
4. Verify that you have entered the correct slot and port numbers.
5. Verify that you have selected a valid frequency for your router.
Setting the Upstream Channel Width
Enter the channel width in hertz (Hz). For NTSC operations, valid values are 200000 Hz
(160 kilosymbols per second [ksps]), 400000 Hz (320 ksps), 800000 Hz (640 ksps), 1600000 Hz
(1280 ksps), and 3200000 Hz (2560 ksps). The default is 1600000 Hz.
If no acceptable channels of the specified width are found, the spectrum management card automatically
begins to scan the upstream spectrum for the next largest available channel width; for example, if the
spectrum management card is unable to find a usable 1.6 MHz upstream channel, it automatically begins
searching for usable 800 kHz channels.