[cisco-voip] Multicast MoH Delay

[Daniel]

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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