Multicast shuts down WAN

[michael.ball]

Every time I use Ghost in multicast mode to image machines my 1721 WAN router which plugs into my 2950 switch stack stops talking to all my branches. Is there a way to disable multicast on either the router or it's port on the switch?

[matthew.mcbride]

Hello Michael,

The 2950 series switch supports igmp snooping. Enabling this feature will limit the flooding of multicast frames only to ports with receivers of the multicast stream.

I hope this is informative.

-m2

[Pavel Bykov]

if you are using multicasts only in your local LAN, then make sure that ip multicast-routing is turned off and that no multicast routing protocol is enabled (no ip pim) on the interface of 1721 that connects to 2950.

How do you know that it stops talking to all your branches? routing protocol convergence?

[ekiriakos]

I wonder if the problem on your router is because it gets overwhelmed by the traffic even though it may not be fully processing it. Have you checked the cpu utilisation when the problem occurrs?

Until you figure out what exactly is going on, you may want to limit the multicast packets that reach the router by configuring storm control on the switch port to which the router connects to.

http://www.cisco.com/univercd/cc/td/doc/product/lan/cat2950/12122ea5/2950scg/swtrafc.htm#wp1229854

int f0/x

storm-control multicast level 1

This will limit the amount of multicast allowed to 1% of the interface bandwidth.

Rgds

E.