Siemens RUGGEDCOM ROX II User Manual page 338

Chapter 8
Layer 2
Figure 7: Example – Combined Router and Switch IGMP In Operation
1. Producer 2. Multicast Router 1 3. Multicast Router 2 4. Switch 5. Host
In this example:
• P1, Router 1, Router 2 and C3 are on VLAN 2
• P2 and C2 are on VLAN 3
• C1 is on both VLAN 2 and 3
Assuming that router 1 is the querier for VLAN 2 and router 2 is simply a non-querier, the switch will periodically
receive queries from router 1 and maintain the information concerning which port links to the multicast router.
However, the switch port that links to router 2 must be manually configured as a router port. Otherwise, the
switch will send neither multicast streams nor joins/leaves to router 2.
Note that VLAN 3 does not have an external multicast router. The switch should be configured to operate in its
routerless mode and issue general membership queries as if it is the router.
• Processing Joins
If host C1 wants to subscribe to the multicast streams for both P1 and P2, it will generate two membership
reports. The membership report from C1 on VLAN 2 will cause the switch to immediately initiate its own
membership report to multicast router 1 (and to issue its own membership report as a response to queries).
The membership report from host C1 for VLAN 3 will cause the switch to immediately begin forwarding
multicast traffic from producer P2 to host C2.
• Processing Leaves
When host C1 decides to leave a multicast group, it will issue a leave request to the switch. The switch will poll
the port to determine if host C1 is the last member of the group on that port. If host C1 is the last (or only)
member, the group will immediately be pruned from the port.
Should host C1 leave the multicast group without issuing a leave group message and then fail to respond to a
general membership query, the switch will stop forwarding traffic after two queries.
When the last port in a multicast group leaves the group (or is aged-out), the switch will issue an IGMP leave
report to the router.
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P1
1
P2
2
C1 C2
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RUGGEDCOM ROX II
CLI User Guide
3
4
C3
IGMP