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Configure a SONET Frame Checksum

Purpose

After you have checked the FCS and determined that a problem exists, you might need to do one of the following, depending on the situation:

Note: By default, SONET interfaces use a 16-bit frame checksum. You can configure a 32-bit checksum, which provides more reliable packet verification. However, some older equipment may not support 32-bit checksums.


Return to the Default 16-Bit Checksum

Action

To return to the default 16-bit frame checksum, follow these steps:

  1. In configuration mode, go to the following hierarchy level:
    [edit]
    user@host# edit interfaces so-fpc/pic/port sonet-options
  2. Delete the fcs 32 statement from the configuration:
    [edit]
    user@host# delete fcs 32
  3. Verify the deletion:
    user@host# show
  4. Commit the configuration:
    user@host# commit

Configure a 16-Bit Checksum

Action

To explicitly configure the 16-bit checksum, follow these steps:

  1. In configuration mode, go to the following hierarchy level:
    [edit]
    user@host# edit interfaces so-fpc/pic/port sonet-options
  2. Configure the 16-bit checksum:
    [edit interfaces so-fpc/pic/port sonet-options]
    user@host# set fcs 16
  3. Verify the configuration:
    user@host# show

    For example:

    [edit interfaces so-0/0/0 sonet-options]
    user@host# show
    fcs 16;
  4. Commit the configuration:
    user@host# commit

Configure a 32-Bit Checksum

Action

To explicitly configure the 32-bit checksum, follow these steps:

  1. In configuration mode, go to the following hierarchy level:
    [edit]
    user@host# edit interfaces so-fpc/pic/port sonet-options
  2. Configure the 32-bit checksum:
    [edit interfaces so-fpc/pic/port sonet-options]
    user@host# set (fcs 32 | rfc-2615)

    Note: The rfc-2615 statement automatically configures the interface to use FCS 32 and changes the C2 byte to 0x16, as per the RFC.

  3. Verify the configuration:
    user@host# show

    For example:

    [edit interfaces so-0/0/0 sonet-options]
    user@host# show
    fcs 32;

    or

    [edit interfaces so-0/0/0 sonet-options]
    user@host# show
    rfc-2615;
  1. Commit the configuration:
    user@host# commit

    Note: On a Channelized OC12 interface, the sonet-options fcs statement is not supported. To configure FCS on each DS3 channel, you must include the t3-options fcs statement in the configuration for each channel.

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