Configuring Cyclic Redundancy Checks; Setting The Cable Length - Cisco PA-2E3 Installation And Configuration Manual

Configuring Cyclic Redundancy Checks
Specifying E3 Framing
In interface configuration mode, specify E3 framing by entering the framing {g751 | bypass}
configuration subcommand, as in the following example:
router(config-if)# framing g751
Use the
Note
must be set to the default, 0; and the DSU bandwidth must be set to the default, 34010.

Setting the Cable Length

In interface configuration mode, set the cable length (0 to 450 feet), as in the following example:
router(config-if)# cablelength 250
Use the
Configuring Cyclic Redundancy Checks
The PA-E3 uses a 16-bit cyclic redundancy check (CRC) by default; it also supports a 32-bit CRC.
The CRC is an error-checking technique that uses a calculated numeric value to detect errors in
transmitted data. The sender of a data frame divides the bits in the frame message by a predetermined
number to calculate a remainder or frame check sequence (FCS). Before sending the frame, the
sender appends the FCS value to the message so that the frame contents are exactly divisible by the
predetermined number. The receiver divides the frame contents by the same predetermined number
that the sender used to calculate the FCS. If the result is not 0, the receiver assumes that a
transmission error occurred and sends a request to the sender to resend the frame.
Note
(enter configuration mode and specify the slot and port address of the PA-E3, and the interface port
number for a VIP2), and then enter the command crc 32. Enter Ctrl-Z to exit from configuration
mode.
For a Cisco 7100 series, Cisco 7200 series, or Cisco uBR7200 series router, use the following
example:
router# configure terminal
Enter configuration commands, one per line.
router(config)#
router(config)# interface serial 3/0
router(config-int)# crc 32
Ctrl-z
8-10 PA-E3 Serial Port Adapter Installation and Configuration
form of this command to return to the default, which is G.751 framing.
no
If you use the bypass option, scrambling must be set to the default, disabled; the DSU mode
form of this command to return to the default, which is 10 feet.
no
To enable a 32-bit CRC on an interface, follow Step 1 and Step 2 of the preceding procedure
End with CNTL/Z.