[cisco-voip] Multicast MoH Delay

[Daniel]

Thanks all for your replies

I would rather use sparse mode to take use of the join messages etc.. so
that the phones join and leave the group. Dense mode I think floods the
network and then prunes interfaces that are not in use, this occurs every 3
minuts or so. It just seems that sparse mode is more precise, I don't have
much experience in this so not sure. Any thoughts / technical reasons on why
to go Sparse, Dense or both?

The RP is on a 6500 with sup720s and MSFC3's, the other distribution switch
is an older 6500 with SUP2s and MSFC2, so c3voip similair to the issue you
had with TAC but the RP is on a different device.

I have added the "ip igmp join-group group-address" command in, this fixes
the issue. My question is with this command, the router will accept and
forward these packets preventing fast switching, if i use the static-group
command the router doesnt accept the packets itself but forwards them thus
allowing fast switching, anyone know of benefits either way? I did
originally have a look at this command but I assumed its use was to always
have the multicast traffic flowing which I didnt think ideal. But it turns
out after actually trying this from Tony's point below it works quite well.
Between the dsitribution switches the mroute is always setup but not from
the distribution switch to the floors, when the phone joins the group the
phones vlan interface is added to the mroute and MoH is heard straight away.
There is no multicast MoH flooding the floor vlans which is what I was
concerned about.








On Thu, Jun 25, 2009 at 5:49 AM, Tony Underwood <tony at cambiumdata.com>wrote:

>  If it's a delay in the route set up then you could try a static igmp join
> on the far end router.
>
> *ip igmp join-group **group-address*
>
>
>
> *Tony Underwood CCIE #7112*
>
> Sr. Network Engineer
>
> Cambium Data Inc.
>
> 5050 So. 111th St.
>
> Omaha, NE 68137
>
> (402) 556-1388
>
> http://www.cambiumdata.com
>
>
>
> *From:* cisco-voip-bounces at puck.nether.net [mailto:
> cisco-voip-bounces at puck.nether.net] *On Behalf Of *Daniel
> *Sent:* Wednesday, June 24, 2009 1:46 AM
> *To:* cisco-voip at puck.nether.net
> *Subject:* [cisco-voip] Multicast MoH Delay
>
>
>
> Hi All,
>
>
>
> I've setup multicast routing for music on hold between our data centre
> network and building floor subnets. The setup is that the data centre is on
> a different subnet and gear to the floor subnets so multicast routing needs
> to be used to get MoH packets to the phones.
>
>
>
> This consists of the following traffic flow,
>
>
>
> MoH Server > Access Switch > Distribution Switch/router(RP) > Distribution
> Switch/router > Floor Switches > Phones
>
>
>
> There are three routing hops (1) from vlan interface to routed interfaces
> of distribution switch (2) between Distribution and (3) from routed
> interface of distributionswitch  to phone vlan interface. Only the
> distribution switches are layer 3.
>
>
>
> The first distribution switch is the RP for the group and only that
> group.The second distribution switch is accepting auto RP only. We are using
> sparse mode.
>
>
>
> Multicast traffic is working, the RP mappings are there, the mroute is
> there, the problem is that when a call is placed on hold there is a 5 second
> delay before the music is heard. I assume this to be somewhat because of the
> join message and the delay of the route or path being setup.
>
>
>
> Anyone know of a way to reduce the delay before music is heard? If not I
> guess its back to the lab.
>
>
>
> regards,
>
>
>
> Dan
>
>
>
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