How to Configure FEC on Nexus 9000 ACI (100G Interface)

[sanjinz85]

Hi everyone,

We’re facing instability on a 100G AOC link between a Leaf (N9K-C9348GC-FX3) and a Spine in our ACI fabric. The transceiver is detected and the interface comes up, but it frequently flaps or goes down unexpectedly.

We're running version 16.0(8e) and suspect the issue may be related to FEC (Forward Error Correction). At the moment, FEC is set to auto-negotiation. We'd like to try forcing it to CL91 to see if that improves link stability.

Could someone please confirm:

• Is there a supported method in ACI to manually set FEC (e.g., via policy group or interface override)?

• Are there other recommended workarounds for stabilizing 100G AOC links on Nexus 9000 with ACI (e.g., specific transceiver compatibility issues, MTU tuning, etc.)?

Thanks in advance for your help!

[Wassim Aouadi]

Hello @sanjinz85 ,

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@sanjinz85 wrote:

• Is there a supported method in ACI to manually set FEC

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Yes. You can define a new Link Level Policy and indicate the desired FEC policy in it: Fabric -> Access Policies -> Policies -> Link Level -> right click -> Create Link Level Policy. Then under Forwarding Error Correction flag you select CL91-RS-FEC: