Administrator Guide

Layer 3 Routing Commands 1509
IGMPv2 introduced a Leave Group message, which is sent by a host when it
leaves a multicast group for which it was the last host to send an IGMP
Report message. Receipt of this message causes the Querier possibly to
reduce the remaining lifetime of its state for the group, and to send a group-
specific IGMP Query message to the multicast group.The Leave Group
message is not used with IGMPv3, since the source address filtering
mechanism provides the same functionality.
IGMPv3 also allows hosts to specify the list of hosts from which they want to
receive traffic. Traffic from other hosts is blocked inside the network. It also
allows hosts to block packets for all sources sending unwanted traffic.
IGMPv3 adds the capability for a multicast router to learn which sources are
of interest to neighboring systems for packets sent to any particular multicast
address. This information gathered by IGMP is provided to the multicast
routing protocol (that is, DVMRP, PIM-DM, and PIM-SM) that is currently
active on the router in order to ensure multicast packets are delivered to all
networks where there are interested receivers.
IGMP mode is automatically enabled when PIM, DVMRP, or IGMP Proxy is
enabled.
Commands in this Section
This section explains the following commands:
ip igmp last-member-query-count
Use the ip igmp last-member-query-count command in Interface
Configuration mode to set the number of Group-Specific Queries sent before
the router assumes that there are no local members on the interface.
ip igmp last-member-query-count ip igmp startup-query-interval
ip igmp last-member-query-interval ip igmp version
ip igmp mroute-proxy show ip igmp
ip igmp query-interval show ip igmp groups
ip igmp query-max-response-time show ip igmp interface
ip igmp robustness show ip igmp membership
ip igmp startup-query-count show ip igmp interface stats
2CSNXXX_SWUM204.book Page 1509 Monday, January 25, 2016 1:25 PM