User manual
27
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IGMP Query Interval:
after
enabling IGMP Query, the interval to check existing multicast members.
MAX Age:
the maximum existing time of the members
6.4.4 GMRP
GMRP Multicast Registration Protocol (GMRP) is a Generic Attribute Registration Protocol (GMRP)
application that provides a constrained multicast flooding facility similar to IGMP snooping. GMRP and
GMRP are industry-standard protocols defined by the IEEE 802.1P. GMRP provides a mechanism that
allows bridges and end stations to dynamically register group membership information with the MAC
bridges attached to the same LAN segment and for that information to be disseminated across all bridges
in the Bridged LAN that supports extended filtering services. The operation of GMRP relies upon the
services provided by the GMRP.
GMRP software components run on both the switch and on the host. On the host, GMRP is typically used
with IGMP: the host GMRP software spawns Layer 2 GMRP versions of the host's Layer 3 IGMP control
packets. The switch receives both the Layer 2 GMRP and the Layer 3 IGMP traffic from the host. The
switch uses the received GMRP traffic to constrain multicasts at Layer 2 in the host's VLAN. In all cases,
you can use IGMP snooping to constrain multicasts at Layer 2 without the need to install or configure
software on hosts.
When a host wants to join an IP multicast group, it sends an IGMP join message, which spawns a GMRP
join message. Upon receipt of the GMRP join message, the switch adds the port through which the join
message was received to the appropriate Multicast group. The switch propagates the GMRP join
message to all other hosts in the VLAN, one of which is typically the Multicast source. When the source is
multicasting to the group, the switch forwards the multicast only to the ports from which it received join
messages for the group. The switch sends periodic GMRP queries. If a host wants to remain in a
multicast group, it responds to the query. In this case, the switch does nothing. If a host does not want to
remain in the Multicast group, it can either send a leave message or not respond to the periodic queries
from the switch. If the switch receives a leave message or receives no response from the host for the
duration of the leave all timer, the switch removes the host from the multicast group.
When using this function, as long as you can enable this feature, if the switch that receives the host IGMP
join information, then the switch will create a multicast group IGMP join information based on the received
join information, and the IGMP port is added to the multicast group, at this time if the destination address
of the data for the multicast group address, then the data only from the members of the multicast group
forwarded out.
