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New Member

Multicast and VSS

HI everyone, 

Having issues with a multicast network, the high level design is:

2-6505s in a VSS (core switch)

all VLAN interfaces are on the core switch

SVI routing

ip multicast routing is enabled

All VLANs have ip pim sparse-dense mode enabled

RP = 10.X.X.X (which also happens to be a VLAN interface)  not sure if this is bad, i usually use a loopback.

All VLAN interfaces have the RP configured to 10.X.X.X

All edge switches (3750 stacks) are configured with the local VLAN and have a etherchannel (2 links) back to the VSS.  Each link goes to each 6506.

Over all the multicast traffic is working, however, we are getting "burst flooding" of the multicast traffic throughout different sections of the network, but not all switches, only some switches receive the "burst flooding".  The burst seems to last for about 20 seconds about every 5-7 mins.

Using the all the show Cli for IGMP, mroute and PIM, everything things seems to be fine, the proper querier is on every VLAN, the proper RP is showing up, groups are being created and membership can be verified.  So I can't figure out why the burst flooding.

Does anyone have any ideas?

Thank you



Re: Multicast and VSS

That is the behaviour of sparse-dense-mode. Try using 'sparse mode' because this is what most people use to prevent this bursting effect you're experiencing.

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New Member

Multicast and VSS

HI Bilal

I will give this a try, but to claify, when i say "burst flooding" the actually mulitcast traffic is appearing on other segments of the network ( i can see it in wireshark as it floods).  I understand that Dense mode "floods" to other PIM routers, but does it also flood the active multicast traffic to other segments of the network, even if it is not being requested?  hope this makes sense