Operation Manual – MulticastH3C S5600 Series Ethernet Switches Chapter 6 IGMP Snooping Configuration6-3z Router port: A router port is a port on the Layer 3 multicast device (DR or IGMPquerier) side of the Ethernet switch. In the figure, GigabitEthernet 1/0/1 of Switch Aand GigabitEthernet 1/0/1 of Switch B are router ports. A switch registers all itslocal router ports in its router port list.z Member port: A member port is a port on the multicast group member side of theEthernet switch. In the figure, GigabitEthernet 1/0/2 and GigabitEthernet 1/0/3 ofSwitch A and GigabitEthernet 1/0/2 of Switch B are member ports. The switchrecords all member ports on the local device in the IGMP Snooping forwardingtable.II. Port aging timers in IGMP Snooping and related messages and actionsTable 6-1 Port aging timers in IGMP Snooping and related messages and actionsTimer Description Message beforeexpiryAction afterexpiryRouter portaging timerFor each router port, theswitch sets a timerinitialized to the agingtime of the route portIGMP generalquery or PIM helloThe switchremoves this portfrom its router portlistMember portaging timerWhen a port joins amulticast group, theswitch sets a timer forthe port, which isinitialized to themember port aging timeIGMP membershipreportThe switchremoves this portfrom the multicastgroup forwardingtable6.1.3 Work Mechanism of IGMP SnoopingA switch running IGMP Snooping performs different actions when it receives differentIGMP messages, as follows:I. When receiving a general queryThe IGMP querier periodically sends IGMP general queries to all hosts and routers onthe local subnet to find out whether active multicast group members exist on thesubnet.Upon receiving an IGMP general query, the switch forwards it through all ports in theVLAN except the receiving port and performs the following to the receiving port:z If the receiving port is a router port existing in its router port list, the switch resetsthe aging timer of this router port.z If the receiving port is not a router port existing in its router port list, the switch addsit into its router port list and sets an aging timer for this router port.
