236 RackSwitch G8000: Application Guide
The Mrouter is learned on the incorrect trunk group
•
Check link state. Trunk group 1 may be down or in STP discarding state.
•
Check STP convergence.
•
Check port VLAN membership.
Hosts receive multicast traffic at a lower rate than normal
•
Ensure a multicast threshold is not configured on the trunk groups.
•
Check link speeds and network congestion.
Additional IGMP Features
The following topics are discussed in this section:
•
“FastLeave” on page 236
•
“IGMP Filtering” on page 236
•
“Static Multicast Router” on page 238
FastLeave
In normal IGMP operation, when the switch receives an IGMPv2 Leave message, it
sends a Group-Specific Query to determine if any other devices in the same group
(and on the same port) are still interested in the specified multicast group traffic. The
switch removes the affiliated port from that particular group, if the following
conditions apply:
•
If the switch does not receive an IGMP Membership Report within the
query-response-interval.
•
If no Mrouters have been learned on that port.
With FastLeave enabled on the VLAN, a port can be removed immediately from the
port list of the group entry when the IGMP Leave message is received. However, if
an Mrouter was learned on that port, the interface remains in the forwarding table.
Note: Only IGMPv2 supports FastLeave. Enable FastLeave on ports that have
only one host connected. If more than one host is connected to a port, you
may lose some hosts unexpectedly.
Use the following command to enable FastLeave.
IGMP Filtering
With IGMP filtering, you can allow or deny a port to send and receive multicast traffic
to certain multicast groups. Unauthorized users are restricted from streaming
multicast traffic across the network.
If access to a multicast group is denied, IGMP Membership Reports from the port
are dropped, and the port is not allowed to receive IPv4 multicast traffic from that
group. If access to the multicast group is allowed, Membership Reports from the
port are forwarded for normal processing.
RS G8000(config)# interface port <port id>
RS G8000(config-if)# no multicast-threshold
RS G8000(config)# ip igmp fastleave <VLAN number>
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