Why you need to give a FEC (with 25GbE networking)

Image: Forward Error Correction in Practice

Some reading on FEC (Forward Error Correction):

3 instances where you need to give a FEC!

1) E-Series with 25GbE for iSCSI

If you’ve got E-Series with 25GbE for iSCSI. And the ports don’t come up, you don’t even get a link light, even though you can see a light coming out the SFP, opposite side to a light going in from the LC/LC cable (so not a cable transposition error), then it might be FEC.

I wasn’t getting any connection until the network guy disabled FEC on the ports.

2) 25Gb card connections on a A300/FAS8200 MCIP using Cisco 3232 switches

From the MCIP guide:

If your AFF A300 or FAS8200 system is configured using 25-Gbps connectivity, you need to set the Forward Error Correction (FEC) parameter manually to off after applying the RCF file.

The RCF file does not apply this setting if the cable connecting the controller module is not inserted into the port.

This task must be performed on all four switches in the MetroCluster IP configuration.


Set the fec parameter to off on each 25-Gbps port, and then copy the running configuration to the startup configuration:

a. Enter configuration mode:
config t
b. Specify the 25-Gbps interface to configure:
interface interface-ID
c. Set fec to off:
fec off
d. Repeat the previous steps for each 25-Gbps port on the switch.
e. Exit configuration mode:

Do a copy run start to save the changes.

 3) On StorageGrid SGA6060 with 25G ports when connected to Cisco

 You might need to change the autonegotiation to auto, using ethtool.

First time is when Pre-Grid environment is booted, login and run ethtool against ports eth3-6.
After reboot that is part of joining grid, login again and now run ethtool against hic1-4.

Fixed in 11.3 or in a hotfix.