Cisco Systems PA-POS-2OC3 manual Configuring Cyclic Redundancy Checks, 4-10, Routerconfig-if# crc

Chapter 4 Configuring the PA-POS-1OC3

Customizing the Configuration

Step 2 To restore loop timing, enter the no clock source internal command or the clock source line command.

Router(config)# interface pos 3/0

Router(config-if)#no clock source internal

Configuring Cyclic Redundancy Checks

The cyclic redundancy check (CRC) default is for a 16-bit CRC. The CRC is an error-checking technique that uses a calculated numeric value to detect errors in transmitted data. The PA-POS-1OC3 also supports a 32-bit CRC. The sender of a data frame calculates the frame check sequence (FCS). The sender appends the FCS value to outgoing messages. The receiver recalculates the FCS and compares it to the FCS from the sender. If a difference exists, the receiver assumes that a transmission error occurred and sends a request to the sender to resend the frame.

Step 1 To configure an interface for a 32-bit CRC, enter the crc 32 command:

Router(config)# interface pos 3/0

Router(config-if)# crc 32

Step 2 To disable the 32-bit CRC and return the interface to the default 16-bit CRC, enter the no crc 32 command.

Router(config)# interface pos 3/0

Router(config-if)# no crc 32

Configuring SONET Payload Scrambling

The default is for SONET payload scrambling to be disabled. SONET payload scrambling applies a self-synchronous scrambler (x^43+1) to the Synchronous Payload Envelope (SPE) of the OC-3 interface to ensure sufficient bit-transition density.

Note Both ends of the connection must use the same scrambling algorithm.

You enable SONET payload scrambling using the pos scramble-atmcommand. (This command has no keywords or arguments.)

Step 1 To enable SONET payload scrambling, use the following command sequence:

Router(config)# interface pos 3/0

Router(config-if)# pos scramble-atm

Router(config-if)# no shutdown

Router(config-if)# end

Step 2 To verify that SONET payload scrambling is enabled on an interface, enter the show startup-configcommand. If scrambling is enabled, the following line is displayed in the configuration:

pos scramble-atm

PA-POS-1OC3 Single-Port Port Adapter Installation and Configuration Guide

4-10 OL-6514-04