Tuesday, July 19, 2011

Multicast Vlan Feature

So, after upgrading to a new version of WLC code, 7.0.116.0 you might notice a new feature in your SSID configs, multicast vlan feature. I wasn't sure what it did so I looked it up and best as I can tell it goes like this.


Enabled per ssid (a handy checkbox or config wlan multicast interface wlan_id enable interface_name)

If you use the VLAN select feature, each client will be listening to the multicast stream on a different VLAN, and the upstream router must send a copy for each VLAN, and multiple copies of a multicast stream are sent out over the air. (not very good use of your air time, and negates some of the purpose of multicast).

Multicast optimization lets you create a multicast vlan, and the controller will make sure all multicast streams go out on the multicast vlan so that the upstream router only sees the single multicast entry for all the VLANs in your pool.

So clients on separate vlans will still only have one single multicast stream over the air.


Since I'm not currently using VLAN pooling I'm not 100% solid on how this would look in the real world but certainly seems a strong feature to have enabled if you were.

5 comments:

AbHiNaV GuPtA said...

sir,
i am trying to configure vlan on 2950 switch.
i created “vlan 10″ at interface 0/1 and “vlan 20″ at interface 0/2
and made 0/24 trunk port.
but problem is when i made vlan 10 up, then automatically vlan 20 shuts down and when i made vlan 20 “UP” then vlan 10 goes “DOWN”
there is no meaning of creating only one vlan.
please help me out.

Wyatt said...

Hello,
try this.
First, a vlan will be down unless there is something plugged into it. Take two computers and plug them into interface 0/1 and 0/2 and see if both vlans come up. If you have a second switch, you could create a trunk with both vlan 10,20 and they should both show up as well. Just to make sure your config should look like:

Config t
vlan 10
exi
vlan 20
exi
interface fas0/1
swi access vlan 10
no shut
interface fas0/2
swi acc vlan 20
no shut


Does this fix the problem?

AbHiNaV GuPtA said...

nope...i did what you said...again its giving same problem..what should i do?

Wyatt said...

Are you trying to place IP addresses on the vlans? Does the switch say INTERFACE vlan XX is down? A 2950 is a layer 2 switch, and you can only have one interface vlan up. These are used for a single IP address to manage the switch. Perhaps this is what is going on...

Unknown said...

He has an older "dumb" layer 2 switch. Older layer 2 switches will allow only one layer 3 SVI up/up at a time and will automatically shut down additional VLANs that have an IP address assigned to them.