Dell PowerConnect M6220, User Configuration Manual

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710
Configuring L2 Multicast Features
For information about configuring a PowerConnect
M6220/M6348/M8024/M8024-k switch as a multicast router that also
performs IGMP snooping, see "Configuring Multicast VLAN Routing With
IGMP and PIM-SM" on page 1261.
What Are GARP and GMRP?
Generic Attribute Registration Protocol (GARP) is a general-purpose protocol
that registers any network connectivity or membership-style information.
GARP defines a set of switches interested in a given network attribute, such
as VLAN ID or multicast address.
PowerConnect M6220, M6348, M8024, and M8024-k switches can use GARP
functionality for two applications:
• GARP VLAN Registration Protocol (GVRP) to help dynamically manage
VLAN memberships on trunk ports.
• GARP Multicast Registration Protocol (GMRP) to help control the
flooding of multicast traffic by keeping track of group membership
information.
GVRP and GMRP use the same set of GARP Timers to specify the amount of
time to wait before transmitting various GARP messages.
NOTE:
If a multicast source is connected to a VLAN on which both L3 multicast
and IGMP snooping are enabled, the multicast source is forwarded to the
mrouter ports that have been discovered when the multicast source is first seen.
If a new mrouter is later discovered on a different port, the multicast source data
is not forwarded to the new port. Likewise, if an existing mrouter times out or
stops querying, the multicast source data continues to be forwarded to that port.
If a host in the VLAN subsequently joins or leaves the group, the list of mrouter
ports is updated for the multicast source and the forwarding of the multicast
source is adjusted. The workaround to this limitation is to statically configure
mrouter ports when enabling IGMP snooping in L3 multicast enabled VLANs.
NOTE:
If MVR is enabled, IP Multicast should be disabled. Multicast routing and
MVR cannot coexist on a switch.