Configuring a SONET Frame Checksum
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. |
Returning to the Default 16-Bit Checksum
Action
To return to the default 16-bit frame checksum, follow these steps:
- In configuration mode, go to the following hierarchy level:[edit]user@host# edit interfaces so-fpc/pic/port sonet-options
- Delete the fcs 32 statement from the configuration:[edit]user@host# delete fcs 32
- Verify the deletion:user@host# show
- Commit the configuration:user@host# commit
Configuring a 16-Bit Checksum
Action
To explicitly configure the 16-bit checksum, follow these steps:
- In configuration mode, go to the following hierarchy level:[edit]user@host# edit interfaces so-fpc/pic/port sonet-options
- Configure the 16-bit checksum:[edit interfaces so-fpc/pic/port sonet-options] user@host# set fcs 16
- Verify the configuration:user@host# show
For example:
[edit interfaces so-0/0/0 sonet-options]user@host# show fcs 16; - Commit the configuration:user@host# commit
Configuring a 32-Bit Checksum
Action
To explicitly configure the 32-bit checksum, follow these steps:
- In configuration mode, go to the following hierarchy level:[edit]user@host# edit interfaces so-fpc/pic/port sonet-options
- 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.
- 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;
- 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.
