Wireless Access

When enabling  bcmc optimization on a vlan does it cause any interruption in service or cause anything to reboot? Is there a good way to test to see if it might be causing issues after enabling like making multicast devices not work?

Hi jprovine,

BCMC (vlan setting) will drop all the broadcast and multicast frames on a VLAN (both wired and wireless) except for ARP, DCHP, IPv6 router advertisement, IPv6 neighbor solicitation and VRRP traffic.

If your clients does not have a multicast applications you can enable this function.

Basically there are three main methodes for broadcast optimalization:

1. Drop broadcast and multicast (at the vap-profile level).

2. Convert broadcast ARP requests to unicaste (vap-profile level). turn it on if option1 is turned on

3. BCMC optimalization (vlan setting)

Please dont confuse this with BC/MC rate optimalization  or DMO and VMRO.

I was planning on doing it on a per vlan basis. So how would it drop wired traffic?

I had found this information online already -

BCMC (is a vlan interface-based knob that drops all broadcast-multicast traffic except ARP,DHCP, VRRP,IPv6 RA and NS. If you are doing multicast it might drop multicast traffic. It stops flooding to other wired port and Ethernet tunnels)

We do have some multicast traffic like mersive solstice and some mac devices.

But my real question is how can I tell if it is affecting that traffic? Will it cause any reboot or interruption in operations. How do you know if you should use it? It is including in the best practices.

I haven't done the DMO or drop broadcast and unknown on all SSID’s

yet but again it is suggested in best practices and I am evaluating these to would be a benefit to my network.

I have already instituted DFS

BCMC drop the broadcast and multicast traffic. If you have multicast applications at all....DONT use this per vlan option.

From "the air" 802.11 frame perspective multicast will be send by using the lowest support data rate. What cause a very bad performance in multicast streams. That is where DMO or DMMO in the vap-profile kicks in.

• DMO translate multicast at the controller to unicast traffic send to the AP and 802.11 to the clients.
• DDMO translate multicast at the AP to unicast traffic send to the AP and 802.11 to the client.

Also recommend to take a look a the Aruba Airgroup feature.

Maybe this thread helps you.

https://community.arubanetworks.com/t5/Controller-Based-WLANs/What-is-the-impact-of-Airgroup-on-BCMC-Optimization/ta-p/175178