Snooping Switch Restrictions; Partial Igmpv3 And Mldv2 Support; Mac Address-Based Multicast Group; Igmp Snooping In A Multicast Router - Dell PowerConnect 8024 User Configuration Manual

Snooping Switch Restrictions

Partial IGMPv3 and MLDv2 Support

The IGMPv3 and MLDv2 protocols allow multicast listeners to specify the
list of hosts from which they want to receive the traffic. However the
PowerConnect snooping switch does not track this information.
IGMPv3/MLDv2 Report messages that have the group record type
CHANGE_TO_INCLUDE_MODE with a null source list are treated as
Leave messages. All other report messages are treated as IGMPv2/MLDv1
Report messages.

MAC Address-Based Multicast Group

The L2 multicast forwarding table consists of the IP Multicast group MAC
address. For IPv4 multicast groups, 16 IP multicast group addresses map to
the same multicast MAC address. For example, 224.1.1.1 and 225.1.1.1 map
to the MAC address 01:00:5E:01:01:01, and IP addresses in the range [224-
239].3.3.3 map to 01:00:5E:03:03:03. As a result, if a host requests 225.1.1.1,
then it might receive multicast traffic of group 226.1.1.1 as well.

IGMP Snooping in a Multicast Router

IGMP snooping is a Layer 2 feature and is achieved by using the L2 multicast
forwarding table. However when multicast routing is enabled on a
PowerConnect switch, L2 multicast forwarding entries do not affect multicast
data forwarding. Instead, corresponding IP multicast table entries need to be
created to achieve similar behavior.
On a multicast router, for IGMP snooping to be functional, any multicast
routing protocol needs to be operationally enabled on the routing interface.
IGMP snooping also needs to be enabled on the VLAN corresponding to the
routing interface. Note that IGMP snooping behavior will not be functional
on VLANs that are not enabled for VLAN routing.
Topologies Where the Multicast Source Is Not Directly Connected to the
Querier
If the multicast source is not directly connected to a multicast querier, it is
likely that the multicast stream is dropped at intermediate snooping switches.
This causes hosts in certain network segments not to receive the multicast
687
Configuring L2 Multicast Features