Auto
(Default) Causes the switch to interpret IGMP packets and to filter IP multicast traffic based on the IGMP
packet information for ports belonging to a multicast group. This means that IGMP traffic will be forwarded
on a specific port only if an IGMP host or multicast router is connected to the port.
Blocked
Causes the switch to drop all IGMP transmissions received from a specific port, and also blocks all
outgoing IP Multicast packets for that port, thus preventing IGMP traffic from moving through specific ports.
Forward
Causes the switch to forward all IGMP and multicast transmissions through the port.
Operation with or without IP addressing
This feature helps to conserve IP addresses by enabling IGMP to run on VLANs that do not have an IP
address. See
Operation with or without IP addressing
Querier capability
The switch performs querier function for IGMP on VLANs having an IP address when there is no other device
in the VLAN acting as querier. See
About using the switch as querier
NOTE:
Whenever IGMP is enabled, the switch generates an Event Log message only after the querier
election.
IP multicast traffic groups are identified by IP addresses in the range of 224.0.0.0 to
239.255.255.255. Also, incoming IGMP packets intended for reserved, or "well-known" multicast
addresses, automatically flood through all ports (except the port on which the packets entered the
switch.)
Number of IP multicast addresses allowed
The number of IGMP filters (addresses) and static multicast filters available is 2,038. Additionally, 16 static
multicast filters are allowed, If multiple VLANs are configured, then each filter is counted once per VLAN in which
it is used.
The following table shows the number of IGMP and static multicast filters available per platform.
Table 1: IP multicast address per platform
Multicast Group Filters
5400R
3810M
3800
IPv4
2038
2038
2038
IPv6
2037
2037
2037
How IGMP operates
IGMP is an internal protocol of the IP suite. IP manages multicast traffic by using switches, multicast routers, and
hosts that support IGMP. A multicast router is not necessary as long as a switch is configured to support IGMP
with the
querier
feature enabled. A set of hosts, routers, and/or switches that send or receive multicast data
streams to or from the same sources is called a
multicast group
, and all devices in the group use the same
multicast group address. The multicast group running version 2 of IGMP uses three fundamental types of
messages to communicate:
30
Aruba 3810 / 5400R Multicast and Routing Guide for ArubaOS-
Switch 16.08