Example: Sending a Multicast Stream

Sending a Multicast Stream with No Directly Attached Hosts

Sending a Multicast Stream with No Directly Attached Hosts provides an example of IGMP processing on Extreme Networks devices when there are no directly attached hosts.

1. A single IP multicast server, with no directly attached hosts, sends a multicast stream into the network via Switch 1.
2. Because IGMP snooping is disabled, Switch 1 floods the multicast stream to all ports the multicast stream to all ports on the ingress VLAN.

   Each router performs an IGMP forwarding check to see if there are any hosts that want to join the multicast group on its locally attached network. Each router drops multicast packets until a host joins the group using one of the following messages:

   • solicited join (sent in response to an IGMP query produced by the router‘s interface)

     In Sending a Multicast Stream with No Directly Attached Hosts, this type of exchange occurs between Router 1 and Host 1 when:

   • Router 1 sends a query to potential Host 1.
   • Host 1 responds with a join message.
   • Router 1 forwards the multicast stream.
   • unsolicited join (sent as a request without receiving an IGMP query first)

     In Sending a Multicast Stream with No Directly Attached Hosts, this type of exchange occurs between Router 2 and Host 2 when:

   • Host 2 sends a join message to Router 2.
   • Router 2 forwards the multicast stream to Host 2.
   • When it no longer wants to receive the stream, Host 2 can do one of the following:
     • - Send a leave message to Router 2.
     • - Time out the IGMP entry by not responding to further queries from Router 2.