H3C Technologies H3C S12500 Series Switches - Manual (Page 38)

22
Configuring a port as a simulated member host
Generally, a host that runs IGMP can respond to IGMP queries. If a host fails to respond, the multicast
router might deem that no member of this multicast group exists on the subnet, and removes the
corresponding forwarding path.
To avoid this situation, you can 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 member 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 you disable the simulated joining function on the port, the switch sends an IGMP leave
message through the port.
To configure a port as a simulated member host:
Step Command Remarks
1. Enter system view. system-view N/A
2. Enter Layer 2 Ethernet
interface view or Layer 2
aggregate interface view, or
enter 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
Use either method.
3. Configure the port as a
simulated member host.
igmp-snooping host-join
group-address [ source-ip
source-address ] vlan vlan-id
A port is not a simulated member
host by default.
NOTE:
Unlike a static member port, a port configured as a simulated member host will age out like a dynamic
member port.
Enabling IGMP snooping fast-leave processing
The IGMP snooping fast-leave processing feature enables the switch to process IGMP leave messages
quickly. With the IGMP snooping fast-leave processing feature enabled, when the switch receives an
IGMP leave message on a port, it immediately removes that port from the forwarding entry for the
multicast group specified in the message. Then, when the switch receives IGMP group-specific queries for
that multicast group, it does not forward them to that port.
On a port that has only one host attached, you can enable IGMP snooping fast-leave processing to save
bandwidth and resources. However, on a port that has multiple hosts attached, do not enable IGMP
snooping fast-leave processing if you have enabled dropping unknown multicast data globally or for the
port. Otherwise, if a host on the port leaves a multicast group, the other hosts attached to the port in the
same multicast group cannot receive the multicast data for the group.