HP MSR2000/3000/4000 Router Series IP Multicast Configuration Guide

16
Aging timers for dynamic ports in IGMP snooping
Timer Description
Message received before
the timer ex
p
ires
Action after the timer
ex
p
ires
Dynamic
router port
aging timer.
When a port recieves an IGMP
general query with the source
address other than 0.0.0.0 or PIM
hello message, the switch starts or
resets an aging timer for it. When
the timer expires, the dynamic
router port ages out.
IGMP general query with the
source address other than
0.0.0.0 or PIM hello
message.
The switch removes the
port from its router port
list.
Dynamic
member port
aging timer.
When a port dynamically joins a
multicast group, the switch starts or
resets an aging timer for the port.
When the timer expires, the
dynamic member port ages out.
IGMP membership report.
The switch removes the
port from the IGMP
snooping forwarding
table.
NOTE:
In IGMP snooping, only dynamic ports age out. Static ports never age out.
How IGMP snooping works
The ports in this section are dynamic ports. For information about how to configure and remove static
ports, see "Configuring static ports."
I
GMP messages are general query, IGMP report, and leave message. An IGMP snooping-enabled
switch performs differently depending on the message.
General query
The IGMP querier periodically sends IGMP general queries to all hosts and routers identified by the
address 224.0.0.1 on the local subnet to determine whether any active multicast group members exist on
the subnet.
After receiving an IGMP general query, the switch forwards the query to all ports in the VLAN except the
port that received the query. The switch also performs one of the following actions:
• If the port that received the query is a dynamic router port in the router port list, the switch restarts
the aging timer for the port.
• If the port that received the query does not exist in the router port list, the switch adds the port to the
router port list, and starts an aging timer for the port.
IGMP report
A host sends an IGMP report to the IGMP querier for the following purposes:
• Responds to queries if the host is a multicast group member.
• Applies for a multicast group membership.
After receiving an IGMP report from the host, the switch forwards it through all the router ports in the
VLAN, resolves the address of the reported multicast group, and performs one of the following actions:
• If no forwarding entry matches the group address, the switch creates a forwarding entry for the
group, adds the receiving port as a dynamic member port to the forwarding entry, and starts an
aging timer for the port.