According Release Notes for Cisco UCS Manager, Release 4.2(1l) We have a fix for CSCvz43359 Traffic using GENEVE overlay sometimes leaves wrong VNIC when GENEVE Offload is enabled on VIC14xx:
|Defect ID||Symptom||First Bundle Affected||Resolved in Release|
|CSCvz43359||On a Cisco UCS server using an NSX-T topology, data traffic using a GENEVE overlay sometimes left the wrong vNIC when GENEVE Offload was enabled on a VIC 1400 series Fabric Interconnect. This issue is resolved.||4.2(1d)C||4.2(1l)C|
Traffic using GENEVE overlay sometimes leaves wrong VNIC when GENEVE Offload is enabled on VIC14xx
Symptom: Rapid mac moves observed on Fabric Interconnect and northbound switches where mac address belongs to device using GENEVE overlay. pkcatp-uw in ESXi kernel was not able to observe this phenomenon. This was only observable via tcpdump on the physical VIC adapter in the debug shell.
Conditions: This was specifically seen in an NSX-T topology though more general use of GENEVE offloading in the hardware would likely show same behavior. The NSX-T TEP mac addresses should be ‘bound’ to a physical interface unless there is a topology change. In this circumstance, we observed the TEP macs rapidly moving from Fabric A to Fabric B and vice versa while the teaming/load balancing policy was set to Active/Active in ESXi and NSX. NSX-T uses BFD Control frames between hosts and BFD leverages GENEVE. When GENEVE Offloading is enabled in the VIC adapter policy, this causes some small number of these BFD frames to egress the wrong physical link which causes the unexpected mac move behavior on northbound devices.