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Switch Troubleshooting (L3)

Hello Experts,

We have one ESX Server connected with L2 where Vlan 183 configured and the L2 Switch connected with L3 Switch via Trunk Port. No interface is assigned to Vlan 183 on L3 Switch.

VLAN 183 IP configured is on L3 Switch

I am using the commands below to locate the server traffic on which trunk interface being used for V-LAN 183. is a server IP connected on one of the interface of L2 Switch.

name_changed#sh arp | in
Internet          9   XX50.569X.4XXd  ARPA   Vlan183
beanta2-core#sh mac-a
beanta2-core#sh mac-address-table add
beanta2-core#sh mac-address-table address XX50.569X.4XXd
Legend: * - primary entry
        age - seconds since last seen
        n/a - not available

  vlan   mac address     type    learn     age              ports
No entries present.

Well, I can see the MAC but when i try to see of what interface being used then there is no output.

Please advice what could be the caused of this issue?



Switch Troubleshooting (L3)

Are you running Rapid-PVST as your spanning-tree ? RPVST flushes out the mac-address table whenever there is a topology change notification BPDU received.

Are all your access ports interface configured with portfast? Without that if a user port goes up/down, a TCN BPDU will be generated which would flush off the mac address table (RPVST behaviour).

I feel this to be an issue as recently i faced this issue with one of my setup.

Hope this helps.



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