HP MSR2003 User Manual

16
Leave message
An IGMPv1 host does not send any leave messages when it leaves a multicast group. The Layer 2 device
cannot immediately update the status of the port that connects to the receiver host. The Layer 2 device
does not remove the port from the outgoing interface list in the associated forwarding entry until the
aging time for the group expires. For a static member port, this mechanism does not take effect.
An IGMPv2 or IGMPv3 host sends an IGMP leave message to the multicast router when it leaves a
multicast group.
When the Layer 2 device receives an IGMP leave message on a dynamic member port, the Layer 2
device first examines whether a forwarding entry matches the group address in the message.
• If no match is found, the Layer 2 device directly discards the IGMP leave message.
• If a match is found but the matching forwarding entry does not contain the port, the Layer 2 device
immediately discards the IGMP leave message.
• If a match is found and the matching forwarding entry contains the port, the Layer 2 device
forwards the leave message to all router ports in the VLAN. The Layer 2 device does not
immediately remove the port from the forwarding entry. Instead, it adjusts the aging timer for the
port.
After receiving the IGMP leave message, the IGMP querier resolves the multicast group address in the
message. Then, it sends an IGMP group-specific query to the multicast group through the port that
received the leave message.
After receiving the IGMP group-specific query, the Layer 2 device forwards it through all its router ports
in the VLAN and all member ports of the multicast group. Then, it waits for the responding IGMP reports
from the directly connected hosts to check for the existence of members for the multicast group. For the
port that receives the leave message (assuming that it is a dynamic member port), the Layer 2 device also
performs one of the following actions:
• If the port receives an IGMP report before the aging timer expires, the Layer 2 device resets the
aging timer.
• If the port does not receive any IGMP reports when the aging timer expires, the Layer 2 device
removes the port from the forwarding entry for the multicast group.
Protocols and standards
RFC 4541, Considerations for Internet Group Management Protocol (IGMP) and Multicast Listener
Discovery (MLD) Snooping Switches
Feature and hardware compatibility
This feature is supported on the following hardware:
MSR routers installed with the Layer 2 switching module SIC 4GSW, SIC 4GSWP, DSIC 9FSW, DSIC
9FSWP, HMIM 24GSW, HMIM 24GSW-POE, or HMIM 8GSW.
IGMP snooping configuration task list
Task at a
g
lance
Configuring basic IGMP snooping functions:
• (Required.) Enabling IGMP snooping

HP MSR2003 Specifications

General

Brand	HP
Model	MSR2003
Category	Network Router
Language	English