Guidelines - Allied Telesis AT-8100L/8 User Manual

Chapter 42: IGMP Snooping Querier

Guidelines

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The guidelines for IGMP snooping querier are listed here:
 The network can have only one LAN.
 The network can have up to three multicast routers.
 You must enable IGMP snooping on all of the switches that you
assign a querier, plus one extra switch that has IGMP snooping
querier disabled.
 You must enable IGMP snooping querier on all of the switches that
you assign a querier.

Apply IGMP snooping querier to the VLAN on which the queries
are to be sent.
 The VLAN must be assigned a routing interface with an IP address
that is a member of the same network as the host nodes and the
source node of the multicast packets. The switch adds the IP
address to the queries as its source address.
 IGMP snooping querier supports up to three queriers. The active
querier has the lowest IP address.

To assign multiple queriers to a LAN, you need one switch in the
network that has IGMP snooping enabled and IGMP snooping
querier disabled. This switch assigns the active querier by
determining which of the IGMP snooping querier enabled switches
has the lowest IP address.
 If you want to add or remove ports from the VLAN after activating
IGMP snooping querier, you must disable IGMP snooping querier,
modify the VLAN, and then enable it again.
 The switch supports IGMP versions 1, 2, and 3. The switch
typically sends only version 2 messages. If the switch receives a
version 1 message, it sends version 1 messages on all of the
ports. If the switch does not receive any additional version 1 or
version 3 messages for 255 seconds, the switch reverts to sending
version 2 messages.
 If the switch receives a query either from a multicast router or from
another switch with IGMP snooping querier, it suspends IGMP
snooping querier and sends no further queries for 125 seconds. If
the switch does not receive any further queries, it reactivates the
feature and resumes sending queries.
 IGMP snooping querier is supported on the base ports and SFP
modules.