DELL N3000 User Manual

Managing IPv4 and IPv6 Multicast

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For more information about when to use PIM-DM, see "Using PIM-DM as

on page 1343. For more information about when to configure DVMRP, see

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.

What Is IGMP?

The Internet Group Management Protocol (IGMP) is used by IPv4 systems

(hosts, L3 switches, and routers) to report their IP multicast group

memberships to any neighboring multicast routers. The Dell Networking

N2000, N3000, and N4000 series switches performs the multicast router role

of the IGMP protocol, which means it collects the membership information

needed by the active multicast routing protocol. IGMP is automatically

enabled when PIM or DVMRP are enabled via the CLI.
The Dell Networking N2000, N3000, and N4000 series switches also supports

IGMP Version 3. Version 3 adds support for source filtering, which is the

ability for a system to report interest in receiving packets only from specific

source addresses, as required to support Source-Specific Multicast [SSM], or

from all but specific source addresses, sent to a particular multicast address.

Version 3 is designed to be interoperable with Versions 1 and 2.

Understanding IGMP Proxy

IGMP proxy enables a multicast router to learn multicast group membership

information and forward multicast packets based upon the group

membership information. The IGMP Proxy is capable of functioning only in

certain topologies that do not require Multicast Routing Protocols (i.e.,