[c-nsp] multicast on transit LAN

Marco Regini marco.regini at ascotlc.it
Tue Feb 16 06:29:19 EST 2010


I 'am in a serious problem with multicast because my distribution (
Cisco Catalyst 3750) and access apparatus ( Cisco Catalyst 3560)  see
each over via a common

network ( build on the common vlan 100).  Physically they are in
daisy-chain with the gigabit interface, the gigabit are in trunk, all
the L3 interface are SVI.


The problem is to limit the multicast traffic on this vlan because at L2
it is like a broadcast. Have you any suggestions?



I read documentation about CGMP,RGMP but on the notes there is written
that this stuff works only  when multicast routers are connected via a
L2 switch, and regarding the vlan 100 my cisco are both router ( there
is a svi ) and switch.


Another idea is to use IGMP snooping but my multicast receivers/sources
are not in this vlan: so no IGMP traffic pass in this vlan.

My last chance is to proxy the IGMP, let me explain:


Receiver --Vlan7-- Fa0/7.Catalyst3560.Gi0/1---Vlan100-Gi0/1.Catalyst3750


If a configure the Catalyst3560 to proxy the igmp join/leave to upstream
Catalyst3750 perhaps I give a chance to IGMP snooping to start working
on Vlan100.


  Marco Regini


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