Dell PowerConnect 8024, User Configuration Manual

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1170
Managing IPv4 and IPv6 Multicast
When Is L3 Multicast Required on the Switch?
Use the IPv4/IPv6 multicast feature on PowerConnect 8000/8100-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 require 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 697 and "What Is MLD Snooping?" on page 699. 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 698.
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 required on any multicast router that serves IPv4 hosts. IGMP is not
required on inter-router links. MLD is required on any router that serves IPv6
hosts. MLD is not required on inter-router links. 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 1182. For more information about when
to use PIM-SM, see "Using PIM-SM as the Multicast Routing Protocol" on
page 1173. For more information about when to configure DVMRP, see
"Using DVMRP as the Multicast Routing Protocol" on page 1184. Unless
specifically required, IGMP/MLD snooping should be disabled on L3
multicast routers.
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.