Optional Tasks

The following configuration tasks are optional when you configure an HDLC channel on a T3/E3 frame interface:

• Configure the cyclic redundancy check (CRC).
• Configure the HDLC idle character.
• Enable data inversion on the interface.
• Set the time interval for monitoring bit and packet rates.
• Set the maximum receive unit (MRU).
• Set the maximum transmit unit (MTU).
• Assign a text description or an alias to the serial interface.

crc

• Use to configure the size of the CRC.
• Specify the number of bits per frame (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 value, 16.
• See crc.

idle-character

• Use to configure the HDLC idle character.
• The idle character is sent between HDLC packets.
• Specify one of the following idle characters:
  • flags—Sets the idle character to 0x7E
  • marks—Sets the idle character to 0xFF
• Example

  host1(config-if)#idle-character marks

• Use the no version to restore the default value, 0x7E (flags).
• See idle-character.

interface serial

• Use to configure a serial interface in the slot/port format.
  • slot—Number of the slot in which the line module resides in the chassis
  • port—Number of the port on the I/O module
• Example

  host1(config)#interface serial 3/0

• Use the no version to disable the interface.
• See interface serial.

invert data

• Use to enable data stream inversion for the interface.
• Enable data stream inversion only if it is turned on at the other end of the line.
• Example

  host1(config-if)#invert data

• Use the no version to disable the feature.
• See invert data.

load-interval

• Use to set the time interval at which the router calculates bit and packet rate counters.
• Choose a multiple of 30 seconds, in the range 30–300 seconds.
• Example

  host1(config-if)#load-interval 90

• Use the no version to restore the default value, 300 seconds.
• See load-interval.

mru

• Use to configure the MRU size for the interface.
• Specify a value in the range 4–9996 bytes.
• Coordinate this value with the network administrator on the other end of the line.
• If you set this parameter to a different value for another protocol, such as IP, the router uses the lower value. This could produce unexpected behavior in your network.
• Example

  host1(config-if)#mru 1500

• Use the no version to restore the default, 1600 bytes.
• See mru.

mtu

• Use to configure the MTU size for the interface.
• Specify a value in the range 4–9996 bytes.
• Coordinate this value with the network administrator on the other end of the line.
• If you set this parameter to a different value for another protocol, such as IP, the router uses the lower value. This could produce unexpected behavior in your network.
• Example

  host1(config-if)#mtu 1500

• Use the no version to restore the default, 1600 bytes.
• See mtu.

serial description

• Use to assign a text description or an alias to a serial HDLC interface.
• You can use this command to help you identify the interface and keep track of interface connections.
• The description or alias can be a maximum of 80 characters.
• Use the show interfaces serial command to display the text description.
• Example

  host1(config-if)#serial description boston09 hdlc channel

• Use the no version to remove the text description or alias.
• See serial description.

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