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We have seen that a router can be in one of two states with
respect to its query status on the network, being either the Querier
or the Non-Querier, as shown in Figure 3-16. An IGMPv2-enabled
router starts in the Initial state, sends a General Membership Query
message, and sets the General Query timer. Whenever the General
Query Timer expires, the timer is reset and a General Membership
Query message is sent. If a router in the Querier state hears a
General Membership Querier message from a router with a lower IP
address, then the router makes a transition from the Query state to
the Non-Querier state and sets the Other Querier Present Timer.
While in the Non-Querier state, this Other Querier Present Timer is
reset each time a General Membership Query is received from a router
with a lower IP address. If the timer times out, then no General
Membership Queries have been received during the Other Querier
Present time and the router changes from the Non-Querier state to
the Query state. |
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