Multicast filtering
7278_en_04 PHOENIX CONTACT 5-3
IGMP Snooping
In IGMP snooping, the switch passively listens in on the IGMP messages that are sent over
the network and dynamically creates the appropriate groups. The groups are not saved and
will be lost on every power down or when switching off the snooping function.
IGMP Query
An LMS with activated query function actively sends queries at "query intervals" and
evaluates the received reports. The LMS only sends IGMP query reports if IGMP snooping
is enabled and only in the management VLAN.
5.2.1.3 Multicast registration with GMRP
GMRP (GARP Multicast Registration Protocol) enables the distribution of multicast group
destination addresses to Layer 2 devices that do not support IGMP snooping. After a
multicast device has registered with the switch (e.g., by means of an IGMP report), the
switch sends a GMRP broadcast packet to all GARP switches, which contains the multicast
group destination address and indicates whether the switch is joining or leaving the group.
The other switches can thus create their own multicast groups and add the receive port to
the group. By default, GMRP is activated as soon as IGMP snooping is activated. The
switches that receive the GMRP packets do not have to support IGMP snooping in order to
receive and evaluate the GMRP packets.
To Next Page
Loading...
