IGMP Details
Router:
sends Membership Query messages to All Hosts (224.0.0.1)
query-interval = 125 secs default
router with lowest IP address is Querier (rest non-queriers)
If lower-IP address query heard, backoff to non-querier state
Other Querier Present Interval default: (robust-count x query-interval) +
(0.5 x query-response-interval) = 255 secs
listens for reports (whether querier or not) and adds group to membership
list for that interface
query-response-interval = 10 secs default
timeout (Group member interval) default:
(robust-count x query-interval) + (1 x query-response-interval) =
260 sec
robust-count - provides fine-tuning to allow for expected packet loss on a
subnet. Default = 2 (tunable from 2-10)