HP A5500 SI Switch Series Configuration Manual page 313

messages (often called "queries"). A querier election mechanism determines which router will act as the
MLD querier on the subnet.
Initially, every MLD router assumes itself as the querier and sends MLD general query messages
1.
(often called "general queries") to all hosts and routers. The destination address is FF02::1.
Upon identifying a general query, every MLD router compares the source IPv6 address of the query
2.
message with its own interface address. After comparison, the router with the lowest IPv6 address
wins the querier election and all other routers become non-queriers.
All the non-queriers start a timer called the "other querier present timer." If a router receives an
3.
MLD query from the querier before the timer expires, it resets this timer. Otherwise, it assumes the
querier has timed out and initiates a new querier election process.
Joining an IPv6 multicast group
Figure 77 MLD queries and reports
Router A
Ethernet
Host A
(G2)
Assume that Host B and Host C will receive IPv6 multicast data addressed to IPv6 multicast group G1,
and Host A will receive IPv6 multicast data addressed to G2, as shown in
process describes how the hosts join the IPv6 multicast groups and how the MLD querier (Router B in the
figure) maintains the IPv6 multicast group memberships:
The hosts send unsolicited MLD reports to the addresses of the IPv6 multicast groups that they will
1.
join, without having to wait for the MLD queries from the MLD querier.
The MLD querier periodically multicasts MLD queries (with the destination address of FF02::1) to all
2.
hosts and routers on the local subnet.
Upon receiving a query message, Host B or Host C (the delay timer of whichever expires first)
3.
sends an MLD report to the IPv6 multicast group address of G1, to announce its membership for
G1. Assume that Host B sends the report message. Upon hearing the report from Host B, Host C,
which is on the same subnet as Host B, suppresses its own report for G1, because the MLD routers
(Router A and Router B) have already determined that at least one host on the local subnet is
interested in G1. This mechanism, called the "MLD report suppression", helps reduce traffic on the
local subnet.
IPv6 network
Host B
(G1)
Query
Report
Querier
Router B
Host C
(G1)
301
Figure 77. The following