Forward Error Correction (FEC) Mode

Intel® Ethernet Adapters and Devices User Guide

ID 705831

Date 06/24/2024

Version

Public

This feature allows you to set the Forward Error Correction (FEC) mode. FEC improves link stability, but increases latency. Many high quality optics, direct attach cables, and backplane channels provide a stable link without FEC.

The driver allows you to set the following FEC Modes:

Auto FEC: Sets the FEC Mode based on the capabilities of the attached cable.
CL108 RS-FEC: Selects only RS-FEC ability and request capabilities.
CL74 FC-FEC/BASE-R: Selects only BASE-R ability and request capabilities.
No FEC: Disables FEC.

Note:

For devices to benefit from this feature, link partners must have FEC enabled.
Intel® Ethernet 800 Series devices only enable Forward Error Correction (FEC) configurations that are supported by the connected media and which are expected to yield healthy Bit Error Rate (BER) connections.
If you enable the registry keyword AllowNoFECModulesInAuto, Auto FEC negotiation will include No FEC in case your link partner does not have FEC enabled or is not FEC-capable.
- To change this setting in Windows PowerShell, use the Set-IntelNetAdapterSetting cmdlet. For example:
```
Set-IntelNetAdapterSetting -Name "<adapter_name>" -RegistryKeyword
AllowNoFECModulesInAuto -RegistryValue 1
```
- To change this setting in Linux, use ethtool. For example:
```
ethtool --set-priv-flags <ethX> allow-no-fec-modules-in-auto on
```
If you are having link issues (including no link) at link speeds faster than 10Gbps, check your switch configuration and/or specifications. Many optical connections and direct attach cables require RS-FEC for connection speeds faster than 10Gbps. One of the following may resolve the issue:
- Configure your switch to use RS-FEC mode.
- Specify a 10Gbps, or slower, link speed connection.
- If you are attempting to connect at 25 Gbps, try using an SFP28 CA-S or CS-N Direct Attach cable. These cables do not require RS-FEC.
- If your switch does not support RS-FEC mode, check with your switch vendor for the availability of a SW or FW upgrade.

To change this setting in Intel PROSet:

This setting is found on the Advanced tab of the device’s Device Manager property sheet or in the Adapter Settings panel in Intel PROSet ACU.

To change this setting in Windows PowerShell, use the Set-IntelNetAdapterSetting cmdlet. For example:

Set-IntelNetAdapterSetting -Name "<adapter_name>" -DisplayName "FEC Mode" -DisplayValue "Auto FEC"