Internet Group Management Protocol—IGMP
IGMP v1
Queries
Querier sends IGMP query messages to 224.0.0.1 with ttl = 1
One router on LAN is designated/elected to send queries
Query interval 60–120 seconds
Reports
IGMP report sent by one host suppresses sending by others
Restrict to one report per group per LAN
Unsolicited reports sent by host, when it first joins the group