562 CHAPTER 42: IGMP SNOOPING CONFIGURATION
To avoid this situation from happening, you can enable simulated joining on a port 
of the switch, namely configure the port as a simulated member host for a 
multicast group. When an IGMP query is heard, the simulated host gives a 
response. Thus, the switch can continue receiving multicast data.
A simulated host acts like a real host, as follows:
■ When a port is configured as a simulated member host, the switch sends an 
unsolicited IGMP report through that port.
■ After a port is configured as a simulated member host, the switch responds to 
IGMP general queries by sending IGMP reports through that port.
■ When the simulated joining function is disabled on a port, the switch sends an 
IGMP leave group message through that port.
Follow these steps to configure simulated joining:
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■ Each simulated host is equivalent to an independent host. For example, when 
receiving an IGMP query, the simulated host corresponding to each 
configuration responds respectively.
■ Unlike a static member port, a port configured as a simulated member host will 
age out like a dynamic member port.
Configuring Fast Leave
Processing
The fast leave processing feature allows the switch to process IGMP leave group 
messages in a fast way. With the fast leave processing feature enabled, when 
receiving an IGMP leave group message on a port, the switch immediately 
removes that port from the outgoing port list of the forwarding table entry for the 
indicated group. Then, when receiving IGMP group-specific queries for that 
multicast group, the switch will 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.
Configuring fast leave processing globally
Follow these steps to configure fast leave processing globally:
To do… Use the command…  Remarks 
Enter system view system-view - 
Enter the 
corresponding view 
Enter Ethernet port 
view 
interface 
interface-type 
interface-number 
Use either command 
Enter port group 
view 
port-group { manual 
port-group-name | 
aggregation agg-id }
Configure simulated (*, G) or (S, G) joining igmp-snooping 
host-join 
group-address 
[ source-ip 
source-address ] vlan 
vlan-id 
Required
Disabled by default