1140 Managing IPv4 and IPv6 Multicast
When Is L3 Multicast Required on the Switch? 
You use the IPv4/IPv6 multicast feature on the PowerConnect 7000 Series 
switches to route multicast traffic between VLANs on the switch. If all hosts 
connected to the switch are on the same subnet, there is no need to configure 
the IP/IPv6 multicast feature. If the switch does not handle L3 routing, you 
can use IGMP snooping or MLD snooping to manage port-based multicast 
group membership. For more information, see "What Is IGMP Snooping?" on 
page 705 and "What Is MLD Snooping?" on page 705. If the local network 
does not have a multicast router, you can configure the switch to act as the 
IGMP querier. For more information, see "IGMP Snooping Querier" on 
page 705.
If the switch is configured as a L3 switch and handles inter-VLAN routing 
through static routes, OSPF, or RIP, and multicast traffic is transmitted 
within the network, enabling and configuring L3 multicast routing on the 
switch is recommended. 
Determining Which Multicast Protocols to Enable
IGMP is recommended on any switch that participates in IPv4 multicasting. 
MLD is recommended on any switch that participates in IPv6 multicasting. 
PIM-DM, PIM-SM, and DVMRP are multicast routing protocols that help 
determine the best route for IP (PIM and DVMRP) and IPv6 (PIM) multicast 
traffic. For more information about when to use PIM-DM, see "Using PIM-
DM as the Multicast Routing Protocol" on page 1144. For more information 
about when to use PIM-SM, see "Using PIM-SM as the Multicast Routing 
Protocol" on page 1143. For more information about when to configure 
DVMRP, see "Using DVMRP as the Multicast Routing Protocol" on 
page 1146.
What Is the Multicast Routing Table?
Multicast capable/enabled routers forward multicast packets based on the 
routes in the Multicast Routing Information Base (MRIB). These routes are 
created in the MRIB during the process of building multicast distribution 
trees by the Multicast Protocols running on the router. Different IP Multicast 
routing protocols use different techniques to construct these multicast 
distribution trees.