[Bridge] Multicast
Tomo Ceferin
tomo at activetools.si
Thu Jun 9 07:33:44 PDT 2005
True. However, allow me to make two assumptions (true in our case):
1) Bridge implements set_multicast_list() and uses it to learn multicast
groups.
2) IPv4 or IPv6 is attached to bridge - both provide IGMP snooping which in
turn feeds bridge with multicast lists through set_multicast_list().
With both above assumptions true, bridge now has awareness of which ports
belong to which multicast groups, hence removing the need to flood all ports.
Am I getting something wrong?
Tomo
> -----Original Message-----
> From: Guillermo Ibáñez
>
> Just an explanation to distinguish processing of layer 3 multicast
> packets (by routers) from layer 2 multicast frames (by
> bridges). Due to
> the fact that the multicast MAC addresses are not permitted in the
> Ethernet frame as source addresses, multicast MAC addresses
> can not be
> learnt by the bridges, so the processing of multicast addresses by
> bridges consists in broadcasting, flooding frames in all but source
> port, instead of forwarding them only by ports where these addresses
> were learnt.
> Excuse me if it sounds a bit "academic".
> GI
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