Work Mechanism Of Igmp Snooping - H3C S5500-SI Series Manual

Operation Manual – Multicast Protocol
H3C S5500-SI Series Ethernet Switches
Router port: On an Ethernet switch, a router port connects the switch to a multicast
router. In the figure, GigabitEthernet1/0/1 of Switch A and GigabitEthernet1/0/1 of
Switch B are router ports. A switch registers all its local router ports in its router
port list.
Member port: On an Ethernet switch, a member port (also known as multicast
group member port) connects the switch to a multicast group member. In the
figure, GigabitEthernet1/0/2 and GigabitEthernet1/0/3 of Switch A and
GigabitEthernet1/0/2 of Switch B are member ports. The switch records all
member ports on the local device in the IGMP Snooping forwarding table.
Note:
Whenever mentioned in this document, a router port is a router-connecting port on a
switch, rather than a port on a router.
II. Port aging timers in IGMP Snooping and related messages and actions
Table 1-1 Port aging timers in IGMP Snooping and related messages and actions
Timer
Router
port aging
timer
Member
port aging
timer

1.1.3 Work Mechanism of IGMP Snooping

A switch running IGMP Snooping performs different actions when it receives different
IGMP messages, as follows:
I. General queries
The IGMP querier periodically sends IGMP general queries to all hosts and routers on
the local subnet to find out whether multicast group members exist on the subnet.
Upon receiving an IGMP general query, the switch forwards it through all ports in the
VLAN except the receiving port and performs the following to the receiving port:
Description
For each router port, the
switch sets a
initialized to the aging time
of the route port
When a port joins an
multicast group, the switch
sets a timer for the port,
which is initialized to the
member port aging time
1-3
Chapter 1 IGMP Snooping Configuration
Message before
expiry
IGMP general
query or PIM hello
timer message of which
the source
address is
0.0.0.0
IGMP report
message
Action after
expiry
The switch
removes this port
from its router port
not list
The switch
removes this port
from the multicast
group forwarding
table