Cisco 7000 SERIES PA 8 PORT T1 MC ADAPTER WITH CSU DSU 规格指南
4-9
Multichannel DS1/PRI Port Adapter Installation and Configuration
OL-3525-03
Chapter 4 Configuring the Multichannel DS1/PRI Interfaces
Configuring the Interfaces
Step 3
Set the encapsulation used by the interface by entering the encapsulation {frame-relay | hdlc |
ppp | smds | x25} configuration subcommand, as in the following example:
ppp | smds | x25} configuration subcommand, as in the following example:
Router(config-if)# encapsulation ppp
Step 4
In interface configuration mode, set the description by entering the description line up to 80 characters
describing this controller configuration subcommand, as in the following example:
describing this controller configuration subcommand, as in the following example:
Router(config-if)# description PPP channel 5
Step 5
Configure additional interfaces as required.
Step 6
When you have included all of the configuration subcommands to complete the configuration, press
Ctrl-Z to exit configuration mode.
Ctrl-Z to exit configuration mode.
Step 7
Write the new configuration to NVRAM as follows:
Router# copy running-config startup-config
[OK]
Router#
To check the interface configuration using show commands, proceed to the
Configuring Cyclic Redundancy Checks
remainder of this section.
CRC is an error-checking technique that uses a calculated numeric value to detect errors in transmitted
data. All interfaces use a 16-bit CRC (CRC-CITT) by default but also support a 32-bit CRC. The sender
of a data frame calculates the frame check sequence (FCS). Before it sends a frame, the sender appends
the FCS value to the message. The receiver recalculates the FCS and compares its calculation to the FCS
from the sender. If there is a difference between the two calculations, the receiver assumes that a
transmission error occurred and sends a request to the sender to re send the frame.
data. All interfaces use a 16-bit CRC (CRC-CITT) by default but also support a 32-bit CRC. The sender
of a data frame calculates the frame check sequence (FCS). Before it sends a frame, the sender appends
the FCS value to the message. The receiver recalculates the FCS and compares its calculation to the FCS
from the sender. If there is a difference between the two calculations, the receiver assumes that a
transmission error occurred and sends a request to the sender to re send the frame.
Enable 32-bit CRC using the crc 32 command. Before you can enable 32-bit CRC, you must use the
interface serial command (followed by the interface address of the interface) to select the interface on
which you want to enable 32-bit CRC. This command functions in the same way on all supported
platforms.
interface serial command (followed by the interface address of the interface) to select the interface on
which you want to enable 32-bit CRC. This command functions in the same way on all supported
platforms.
Table 4-4
CRC Commands
Purpose
Command
Example
Further Information
Enable 32-bit CRC.
crc size
The example enables 32-bit CRC on a serial
interface:
interface:
Router(config)# interface serial 3/0:0
Router(config-if)# crc 32
Return to default
16-bit CRC.
16-bit CRC.
no crc size
The example disables 32-bit CRC on a serial
interface and returns to the default 16-bit
CRC:
interface and returns to the default 16-bit
CRC:
Router(config)# interface serial 3/0:0
Router(config-if)# no crc 32