H3C Technologies H3C S10500 Series Switches - Manual (Page 40)

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Configuring simulated joining
Generally, a host that runs IGMP can respond to IGMP queries that the IGMP querier sends. If a host fails
to respond, the multicast router might deem that no member of this multicast group exists on the network
segment, and removes the corresponding forwarding path.
To avoid this situation, you can enable simulated joining on a port of the switch. That is, you configure
the port as a simulated member host for a multicast group. When the simulated member host receives an
IGMP query, it gives a response. Therefore, the switch can continue receiving multicast data.
A simulated host acts like a real host in the following ways:
• When a port is configured as a simulated member host, the switch sends an unsolicited IGMP
report through the port, and can respond to IGMP general queries with IGMP reports through the
port.
• When the simulated joining function is disabled on a port, the switch sends an IGMP leave
message through the port.
Follow these steps to configure simulated joining:
To do... Use the command... Remarks
Enter system view system-view —
Enter Layer 2 Ethernet interface
view, Layer 2 aggregate interface
view, or port group view
Enter Layer 2 Ethernet interface view or
Layer 2 aggregate interface view:
interface interface-type interface-number
Enter port group view:
port-group manual port-group-name
Required
Use either command
Configure simulated joining
igmp-snooping host-join group-address
[ source-ip source-address ] vlan vlan-id
Required
Not configured by default.
NOTE:
•
A simulated host is equivalent to an independent host. For example, when a simulated member host
receives an IGMP query, it gives a response separately.
• Unlike a static member port, a port that you configure as a simulated member host ages out like a
dynamic member port.
Configuring fast-leave processing
The fast-leave processing feature enables the switch to process IGMP leave messages quickly. With the
fast-leave processing feature enabled, when the switch receives an IGMP leave message on a port, it
immediately removes that port from the outgoing port list of the entry in the forwarding table for the
indicated group. Then, when the switch receives IGMP group-specific queries for that multicast group, it
does not forward them to that port.
In VLANs where only one host is attached to each port, fast-leave processing helps improve bandwidth
and resource usage. However, if fast-leave processing is enabled on a port that connects to more than
one host, when one host leaves a multicast group, the other hosts that are attached to the port and
interested in the same multicast group cannot receive multicast data for that group. If the function of
dropping unknown multicast traffic is already enabled on the switch or in the VLANs, you should not
enable the fast-leave processing function.