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Some servers are not reachable due to "TX-NNI" entries in ARP table

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TitleSome servers are not reachable due to "TX-NNI" entries in ARP table
Symptoms
Customer has a couple VSP 7400 (v8.0.7) configured as vIST cluster. On one of VSPs they observe TX-NNI entries in the ARP table causing connectivity issue for some servers. 

 
Environment
  • VSP 7400
  • VOSS
Cause
Continuous flapping MACs (Vmware) due to incorrect ESXi configuration. Multiple iterations of FDB output table ( # show vlan mac-address-entry) indicated that some VMware MACs were flapping between UNI ports and IST link (NNI) . Sample output :
 
VLAN: '666' MAC: '00:50:56:99:1a:aa' VENDOR: '00:50:56 -> VMware, Inc.' PORT: 'Port-1/33' OLD_PORT(s): 'MLT-53 Port-1/33 MLT-53'
666 learned 00:50:56:99:1a:aa MLT-53 true VSP-7400-48Y-8C
666 learned 00:50:56:99:1a:aa Port-1/33 false -
666 learned 00:50:56:99:1a:aa MLT-53 true VSP-7400-48Y-8C
666 learned 00:50:56:99:1a:aa Port-1/33 false -

Per above about the host with MAC address "00:50:56:99:1a:aa" was learned from MLT 53 initially then from port 1/33 then from MLT-53 then again from port 1/33 and this happened in 13 seconds.

Resolution
Eliminate MAC address flapping because of incorrect ESXi configuration.
Additional notes

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