Why should we disable BCMC Optimization knob while using wireless bridge on the network?
Wired clients behind the wireless bridge encountering IP conflict/Duplicate IP when BCMC Optimization is enabled under interface VLAN
We recommend disabling BCMC Optimization in the VLANs in a setup which involves wireless bridges like Aruba/HP Bridge 501 , ORing, etc. because it would create a scenario where the wired clients behind the bridge would experience IP conflict.
Below is an example:
Aruba BSSID – 24:de:c6:56:c3:40
Bridge mac address – 88:51:fb:77:d8:4a
The wireless bridge has couple of wired clients connected. These wired clients would be registered in controller with wireless bridge’s address in the user-table.
When BCMC Optimization is enabled:
We can see that from the highlighted packet#936, where the Source and Destination Address is HP-501 bridge which is transmitted by Aruba AP(BSSID - 24:de:c6:56:c3:40)
This packet when received on the windows client behind the bridge, the client assumes this arp is generated by some other client in the network and hence marks this as IP conflict.
Below is the client side packet capture from the wired client(126.96.36.199) behind the bridge
When BCMC Optimization is disabled:
When BCMC Optimization is disabled, we do not see any arp unicast with source and destination as bridge mac address.
Hence, we do not encounter any IP conflict issue
The following is the snip from the receiver laptop which does not experience IP conflict
Hence we recommend disabling BCMC Optimization while using wired clients behind any wireless bridge