GE ML1200 instruction manual IP Multicast Filters, Isolating multicast traffic in a network

IGMP CHAPTER 15: IGMP

Either of these switches can operate as querier because a multicast router is not present on the network. (If an IGMP switch does not detect a querier, it automatically assumes this role, assuming the querier feature is enabled-the default-within IGMP.)

FIGURE 15–2: Isolating multicast traffic in a network

In the above figure, the multicast group traffic does not go to switch 1 and beyond. This is because either the port on switch 3 that connects to switch 1 has been configured as blocked or there are no hosts connected to switch 1 or switch 2 that belong to the multicast group.

For PC 1 to become a member of the same multicast group without flooding IP multicast traffic on all ports of switches 1 and 2, IGMP must be configured on both switches 1 and 2, and the port on switch 3 that connects to switch 1 must be unblocked.

15.1.3 IP Multicast Filters

IP multicast addresses occur in the range from 224.0.0.0 through 239.255.255.255 (which corresponds to the Ethernet multicast address range of 01005e-000000 through 01005e- 7fffff in hexadecimal.) Devices such as the MultiLink ML1200 Managed Field Switch having static Traffic/Security filters configured with a “Multicast” filter type and a “Multicast Address” in this range will continue in effect unless IGMP learns of a multicast group destination in this range. In that case, IGMP takes over the filtering function for the multicast destination address(es) for as long as the IGMP group is active. If the IGMP group subsequently deactivates, the static filter resumes control over traffic to the multicast address formerly controlled by IGMP.

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