Configuring the Switch Modules using the Menu-driven Interface 
Configuring IGMP Snooping 
This section describes how to configure IGMP snooping on a VLAN ID. For information on 
how to set IGMP globally on the switch module and how to setting the IGMP filter mode for 
processing multicast packets, refer to the “Configuring Advanced Switch Module Features” 
section earlier in this chapter. 
Internet Group Management Protocol (IGMP) snooping, when enabled and configured 
properly, manages multicast traffic through a switch module. IP multicast traffic is forwarded 
based on multicast group membership information registered by the switch module. The 
switch module can use IGMP snooping to configure ports dynamically, so that IP multicast 
traffic is forwarded only to those ports associated with IP multicast hosts, based on 
membership information. 
IGMP snooping allows the switch module to recognize IGMP queries and reports sent 
between network stations or devices and an IGMP host that belongs to a specific multicast 
group. When enabled for IGMP snooping, the switch module can open or close a port to a 
specific device based on IGMP messages passing through the module. This feature further 
limits unnecessary broadcasts. The switch module can be configured to make queries using 
either IGMP version 1 or version 2. 
When IGMP snooping is enabled globally on the switch module, you can enable or disable 
individual VLANs for IGMP snooping.  
When IGMP snooping is enabled, any port receiving IGMP response packets will forward 
them to the CPU, and the CPU sets this port as a member of the corresponding multicast 
address.   
The switch module supports three multicast group address filtering modes for making 
forwarding decisions regarding multicast packets. 
• 
• 
• 
Forward all group addresses—All multicast packets destined for all group MAC 
addresses are forwarded according to the VLAN rules. 
Forward all unregistered group addresses—All multicast packets with group MAC 
address registration entries existing in the multicast table (both static multicast and group 
multicast created by IGMP snooping) are forwarded to member ports. If the group MAC 
address does not exist in the multicast table, packets are forwarded according to the 
VLAN rules. 
Filter all unregistered group addresses—All multicast packets with group MAC 
addresses are forwarded only if such forwarding is explicitly permitted by a group 
address entry in the multicast table. If the group MAC address exists in the multicast 
table, then the packets are forwarded using the port member list for that entry. If the 
group MAC address does not exist in the multicast table, the packets are dropped. 
To configure IGMP Snooping: 
1. Highlight Configure IGMP Snooping on the Configuration menu. 
2. Press the Enter key. The following screen is displayed. 
HP ProLiant BL e-Class C-GbE Interconnect Switch Menu-driven Interface Reference Guide  2-33 
 
 
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