Interface Suddenly Stopped Working with Running Service on N540X-16Z8Q

[Shahrier]

Hello Community,

We are facing a critical issue on our Cisco N540X-16Z8Q2C-D router. One of the interfaces that was actively running a live service suddenly stopped working without any prior warning or configuration change.

Details:

Device Model: Cisco N540X-16Z8Q2C-D
IOS Version: 7.7.21

Issue: Interface went down unexpectedly while service was active

Impact: Live service interrupted

No changes or alarms were observed prior to failure

We have checked physical connections and basic interface status, but everything seems normal from the physical layer side. Still, the interface remains down or unresponsive.

Has anyone encountered a similar issue with N540X-16Z8Q2C-D? Any suggestions on where to start the deep troubleshooting—logs to check, hardware diagnostics, or known bugs?

Thanks in advance for your help.

[bigevilbeard]

If you have checked all your L1, 2 and 3 connection, there is no light on the port etc.. You could have a dead interface, its rare, but this happened to a few of my edge XR devices in the day. You can move the cable/configuration to another port to test. then either RMA the device or card should you need to.

Hope this helps.

[Shahrier]

I have encountered two different issues:

1. In one case, the port light was completely off, although optical power was present at both ends.

2. In another case, the physical port was showing as "up," but there was no point-to-point (P2P) connectivity or ARP resolution. After changing the physical port, the issue was resolved.

Is there any specific reason or explanation for this type of behavior?

[bigevilbeard]

In your first case this IMO points to a physical layer issue, fibre/transceiver issues, damaged cables ...  in the second case this points more to a defective Port ASIC/PHY etc.. 

If the problem was with the original interface hardware or its specific internal connectivity, then when you are moving to another interface/port immediately resolves the issue because you are bypassing the faulty component.