Symptom

A Cisco Cat9300 with mGig interfaces may see intermittent link flaps or auto-negotation issues when connected to an mGig capable endpoint such as a Cisco 4800 AP.

Conditions

This is specific to mGig ports on the Cat9300 that go to certain mGig capable endpoints configured with autonegotation for mGig speeds (i.e. 2.5 Gbps, 5 Gbps, etc.).

Workaround

Hard coding the speed to 1gbps on both sides (effectively disabling autonegotation) can stabilize an affected interface.

Further Problem Description