Do not turn on bcmc-optimization on your controller's management VLAN unless...

By cjoseph posted Dec 05, 2011 03:02 PM


bcmc-optimization is a great way to suppress wired and wireless broadcasts on your client vlans.  That is a decent substitute for broadcast and multicast filtering at the virtual-ap, or WLAN level.  The commands:


config t

interface vlan 100



..will suppress all broadcasts on vlan 100, whether or not broadcast filtering is enabled on the virtual AP, so it is like a master switch to suppress broadcasts on that VLAN.  If you have a remote AP that has a wired interface on VLAN 100, the broadcasts will be suppressed there, too, keeping unnecessary traffic from crossing your WAN.  


Where it might break things, however is if you enable this on the management VLAN interface and you have access points that depend on layer-2 discovery (Aruba Discovery Protocol- ADP) to find the controller.  When an access points boots up, it sends out a layer-2 multicast discovery to  If the controller has ADP configured (by default it does) it will respond to the AP, and the AP will contact the controller.  With bcmc-optimization configured on the controller's management interface, it will NOT respond to those APs on that multicast address and they will not find the controller layer-2.


So, long story short, try to avoid configuring this on an controller's VLAN interface where APs need to discovery the controller layer-2

1 comment


Nov 07, 2012 03:13 PM

so the warning in the document (UG) is just about this, does this mean that once it receive a broadcast packet it will drop it what about ARP ?.

whatis the different between it and broadcast filtering ?