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Configuring Higher Layers
You must configure HDLC over the top layer of the T3 interface. See "HDLC Channel
Configuration Tasks" on page 139.
HDLC Channel Configuration Tasks
You must configure HDLC over the T3, T1, unframed E1, or fractional T1/E1 line that
you configure on an interface. As Figure 8 on page 113 shows, HDLC must be the top
layer of the interface stack.
To configure an HDLC channel, specify a serial interface. For example:
Optional Tasks
The following configuration tasks are optional when you configure an HDLC channel
on a channelized T3 interface:
crc
Use the no version to disable transmission of the specified FDL message or all
FDL messages.
See path ds3 t1 fdl transmit.
host1(config)#interface serial 4/0:1/1/1/1
Configure the CRC.
Configure the HDLC idle character.
Enable data inversion on the interface.
Set the MRU.
Set the MTU.
Assign a text description or an alias to the serial interface.
Use to configure the size of the CRC.
Specify the number of bits (16 or 32) that are used to calculate the frame check
sequence (FCS). Both the sender and receiver must use the same setting.
The CRC is an error-checking technique that uses a calculated numeric value to
detect errors in transmitted data.
A 32-bit CRC should be used to protect longer streams at faster rates and,
therefore, provide better ongoing error detection.
Example
host1(config-if)#crc 32
Use the no version to restore the default, 16.
See crc.
Chapter 4: Configuring Channelized OCx/STMx Interfaces
Configuration Tasks
139
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