Igmp Messages; Operating Rules - HP procurve 8100fl series Management And Configuration Manual

N o t e o n I G M P
v e r s i o n 3
s u p p o r t

IGMP Messages

The multicast group running version 2 of IGMP uses three fundamental types
of messages to communicate:
■ Query: A message sent from the querier (multicast router or switch)
asking for a response from each host belonging to the multicast group. If
a multicast router supporting IGMP is not present, then the switch must
assume this function in order to elicit group membership information
from the hosts on the network. (If you need to disable the querier feature,
you can do so through the CLI, using the IGMP configuration MIB. See
"IGMP Show Commands" on page 10-6.)
Report (Join): A message sent by a host to the querier to indicate that
■
the host wants to be or is a member of a given group indicated in the report
message.
■ Leave Group: A message sent by a host to the querier to indicate that the
host has ceased to be a member of a specific multicast group.
When an IGMPv3 Join is received by the switch, it accepts the host request
and begins to forward the IGMP traffic. This means that ports which have not
joined the group and are not connected to routers or the IGMP Querier will
not receive the group's multicast traffic.
The switch does not support the IGMPv3 "Exclude Source" or "Include
Source" options in the Join Reports. Rather, the group is simply joined from
all sources.
The switch does not support becoming a version 3 Querier. It will become a
version 2 Querier in the absence of any other Querier on the network.

Operating Rules

An IP multicast packet includes the multicast group (address) to which the
packet belongs. IGMP identifies members of a multicast group (within a
subnet) and allows IGMP-configured hosts (and routers) to join or leave
multicast groups based on the following operations.
■ When an IGMP client connected to a switch port needs to receive multi­
cast traffic from a specific group, it joins the group by sending an IGMP
report (join request) to the network. (The multicast group specified in the
join request is determined by the requesting application running on the
IGMP client.)
Multimedia Traffic Control with IP Multicast (IGMP)
How IGMP Operates
10-9