When Is L3 Multicast Required On The Switch; What Is The Multicast Routing Table - Dell M6220 User Configuration Manual

When Is L3 Multicast Required on the Switch?

Use the IPv4/IPv6 multicast feature on PowerConnect M6220, M6348,
M8024, and M8024-k 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 705 and "What Is MLD Snooping?" on page 707.
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 706.
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 1192. For more information about when
to use PIM-SM, see "Using PIM-SM as the Multicast Routing Protocol" on
page 1183. For more information about when to configure DVMRP, see
"Using DVMRP as the Multicast Routing Protocol" on page 1194. 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.
1180
Managing IPv4 and IPv6 Multicast