Multicast and Spanning Tree

Multicast and Spanning Tree
It might seem that CGMP and IGMP Snooping are the way to go. That is true—if you have a very
stable network. Remember that STP is used to allow for redundancy but that it disables the
redundant links until they are needed. If you have a switched network with redundant connections
and a link drops, spanning tree takes over and figures out the next best topology. Unfortunately,
the spanning tree process doesn’t tell the multicasting process that this is happening.
The switch will still forward the multicast message out the port that it was using. This can cause
delays and dropped connections. Eventually it settles down, unless the topology changes are
always going on.