Installation guide

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Cisco uBR7100 Series Universal Broadband Router Software Configuration Guide
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Chapter 3 Configuring the Cisco Cable Interface
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. Refer to the “Setting the Upstream Frequency” section on page 3-10,
or the “Creating Spectrum Groups” section on page 3-28 for details.
To activate the upstream ports, use the following commands in global configuration mode.
Verifying the Upstream Ports
To determine if the upstream ports are activated or deactivated, enter the show interface cable command
for the upstream port just configured:
router# show interface cable1/0
Cable1/0 is up, line protocol is up
Hardware is BCM3210 FPGA, address is 00e0.1e5f.7a60 (bia 00e0.1e5f.7a60)
Internet address is 1.1.1.3/24
MTU 1500 bytes, BW 27000 Kbit, DLY 1000 usec, rely 255/255, load 1/255
Encapsulation, loopback not set, keepalive not set
ARP type: ARPA, ARP Timeout 04:00:00
Last input 00:00:25, output 00:00:00, output hang never
Last clearing of “show interface” counters never
Queuing strategy: fifo
Output queue 0/40, 0 drops; input queue 0/75, 0 drops
5 minute input rate 0 bits/sea, 0 packets/sec
5 minute output rate 0 bits/sec, 0 packets/sec
10878 packets input, 853740 bytes, 0 no buffer
Received 3679 broadcasts, 0 runts, 0 giants, 0 throttles
3 input errors, 3 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort
5401 packets output, 645885 bytes, 0 underruns
0 output errors, 0 collisions, 9 interface resets
0 output buffer failures, 0 output buffers swapped out
Setting Upstream Backoff Values
The DOCSIS-specified method of contention resolution for cable modems wanting to transmit data or
requests on the upstream channel is a truncated binary exponential backoff, with the initial backoff
window and the maximum backoff window controlled by the CMTS. The Cisco uBR7100 series CMTS
specifies backoff window values for both data and initial ranging, and sends these values downstream as
part of the Bandwidth Allocation Map (MAP) MAC message.
The values are configurable on the Cisco uBR7100 series software and are power-of-two values. For
example, a value of 4 indicates a window between 0 and 15; a value of 10 indicates a window between
0 and 1023. You can set fixed start and end values for data backoff on the upstream ports, or you can set
the upstream ports for automatic data backoff. You have the same options for ranging backoff. For both
backoff windows, the default start value is 0; the default end value is 4. Valid values are from 0 to 15.
Command Purpose
CMTS01(config)# interface cable slot/port
Specify a cable interface and enter cable interface
configuration mode.
CMTS01(config-if)# no cable upstream
usport shutdown
Enable upstream data traffic.