3Com 5000 ATM manual Enabling Igmp Snooping on CoreBuilder 5000 SwitchModules

Enabling IGMP Snooping on CoreBuilder 5000 SwitchModules 5-7

Enabling IGMP Snooping on CoreBuilder 5000 SwitchModules

IGMP snooping on a CoreBuilder 5000 SwitchModule

IGMP snooping can be enabled on the following CoreBuilder 5000 SwitchModules:

■FTE SwitchModule v1.2

■GigaFTE SwitchModules

When you enable IGMP snooping on either an FTE SwitchModule, v1.2, or a GigaFTE SwitchModule, the IP multicast bit is enabled in the module’s Receive Control Register. This causes the module’s receive state machine to parse all IP packets looking for the IGMP protocol. If the packet is an IGMP packet, it is directed to the management processor queue for snooping purposes.

The management processor then learns the multicast address and adds it to the module’s forwarding tables. When the IP multicast bit in the module’s Receive Lookup Control Register is enabled, the forwarding table entries have a 36-bit destination port map. When a packet enters the module, the processor looks up the address and directs the packet to the allowed destination port map. Figure 5-4 shows a typical FTE DRAM address forwarding entry.

The only difference between the modules when IGMP snooping is enabled is that the IP Multicast Bit is Bit <20> in the FTE, v1.2 module and Bit<13> in the GigaFTE module.