From: Kevin M. Woods (kev@xxxxxxx)
Date: Sat May 13 2000 - 02:28:16 GMT-3
If a router receives a multicast frame and it's not running any multicast
routing protocol then the frame is dropped if the receiving interface is
not a member of the group. If it is a member of the group, it will allow
the frame for itself but not forward it.
A switch will flood the frame just as it will a broadcast, so switched or
not a LAN can successfully use multicast applications.
Kevin
// I have another question regarding multicast, and I can't seem to find th
e answer. Here goes.
// A standard cisco router with no multicast routing enabled. He gets a pac
ket destined for a mulitcast group.
// What does he do with it. Does he drop it? Does he send it to his default gat
eway since he has no path to that address? I know what he does with a unicast,
and I know what he does with a broadcast, both with a helper and without.
// All the literature dicusses the various means of routing multicasts, and
using CGMP to control it at the switch layer, and I'm okay with all of that. B
ut as I have stated before, I have worked on lots of lans that don't have IP mu
lticast turned on, yet use multicast applications. How does multicasting work i
n a routed/switched lan with no bells and whistles (ie. no PIM or IGMP snooping
or CGMP). I just can't seem to find any documentation on that.
// Specifically I think about "ghosting" pc's on a lan.
// Thanks all!
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