[cisco-voip] Multicasting Speakers and Feed IP command

[Robert Kulagowski]

Ian J. Pitts wrote:
> The only way to get from vlan 999 to vlan 10 with multicast is to route it
> and that requires multicast routing on the router.
> 
> If you are using the 3750 for layer 3 routing you will need to upgrade to an
> image that supports it.
> You could also add another router to those vlan's and enable multicast
> routing and ip pim on those layer 3 interfaces.
> 
> Just to clarify the audio path.
> When you enable the feed ip dn you are essentially having the cme instruct
> the calling phone to send it's audio to a multicast address. The packets are
> sourced from the calling phone not the CME. This might be the part that is
> causing the confusion.


Still trying to work through it...

OK, so the router has pim sparse-dense on the two dot1q subinterfaces.

If the phone is in vlan10, and multicast routing is enabled on the 3845, 
then shouldn't that be sufficient to get multicast packets to vlan999 
(and thereby extended over the trunk to the 3750)

There are ip addresses assigned to the two VLANs that exist on the 3750 
(they're 10.255.3.5 and 10.244.3.5; the dot1q on the router is .1 in 
both subnets)

I'm not doing any layer 3 routing per-se on the 3750; it's pretty much 
router-on-a-stick configuration.

I'm not looking to add another router into the mix; I'd like to use what 
I already have.

In any case, I've installed the ip services image onto the 3750, so lets 
see what happens.  Do the two vlan interfaces on the stack master also 
need to have the pim sparse-dense-mode command?