CL74 FEC support for 25-gigabit and 50-gigabit channel speeds

You can disable or reenable clause 74 (CL74) -- as well as CL91 -- forwarding error correction (FEC) support. FEC CL91 is supported for the 100-gigabit port speed and FEC CL74 is supported for both 25-gigabit and 50-gigabit port speeds. FEC CL91 is enabled by default for the 100-gigabit port speed; when the ports are channelized either in 4x25-gigabit or 2x50-gigabit, FEC CL74 is enabled. 

• To disable the FEC mode: [edit] set interfaces interface-name gigether-options fec none 

• To reenable the FEC mode: [edit] delete interfaces interface-name gigether-options fec none or [edit] set interfaces interface-name gigether-options fec (fec74|fec91)
• To check FEC status: show interfaces interface-name

The output for the show command will list FEC statistics for a particular interface-name, including the FEC corrected errors count, the FEC uncorrected errors count, and the type of FEC that was disabled or enabled.