Configuring L2 Multicast Features 701
Enabling MVR and IGMP on the Same Interface
MVR and IGMP snooping operate independently and can both be enabled on
an interface. When both MVR and IGMP snooping are enabled, MVR listens
to the IGMP join and report messages for static multicast group information,
and IGMP snooping manages dynamic multicast groups.
When Are L3 Multicast Features Required?
In addition to L2 multicast features, the switch suports IPv4 and IPv6
multicast features. You configure the IPv4/IPv6 multicast features if the
switch functions as a multicast router that can route multicast traffic between
VLAN routing interfaces. In this case, you must enable a multicast routing
protocol on the switch, such as PIM-SM. For information about L3 multicast
features, see "Managing IPv4 and IPv6 Multicast" on page 1167.
If the switch functions as a multicast router, it is possible to enable both
IGMP and IGMP snooping so that IGMP forwards multicast traffic for
directly connected hosts between VLANs, and IGMP snooping prevents the
multicast router from flooding incoming multicast packets on the ingress
VLAN.
For information about configuring a PowerConnect 8000/8100-series switch
as a multicast router that also performs IGMP snooping, see "Configuring
Multicast VLAN Routing With IGMP and PIM-SM" on page 1251.
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.
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