LiSA

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Port states:

• mrouter (router port)
• subscriber (port belongs to established multicast group)
• none

Forwarding cases (igmp snooping enabled on vlan):

• multicast traffic received on “none” port
  • if no mrouter present, flood to all ports
  • otherwise flood to mrouter ports
• igmp received on “none” port
  • if no mrouter present, ignore frame (no group is created)
  • otherwise
    • creates multicast group
    • forwards to mrouter ports only
• multicast traffic received on “mrouter” port
  • send to established group members only
• igmp received on “mrouter” port
  • creates multicast group
  • forwards to mrouter ports only

Other notes:

• if igmp snooping is disabled, multicast traffic is flooded to all ports in vlan, regardless of frame nature (i.e. it is igmp or not); static multicast fdb entries are ignored;
• mrouters can be statically configured while igmp snooping is disabled on vlan, but they are ignored until igmp snooping is enabled; when igmp snooping is enabled, the rules listed above apply;