Dell PowerConnect 7048P User Manual - Page 78

IGMP Snooping Querier When Protocol Independent Multicast (PIM) and IGMP are enabled in a network with IP multicast routing, the IP multicast router acts as the IGMP querier. However, if the IP-multicast traffic in a VLAN needs to be Layer 2 switched only, an IP-multicast router is not required. The IGMP Snooping Querier can perform the IGMP snooping functions on the VLAN. MLD Snooping In IPv4, Layer 2 switches can use IGMP Snooping to limit the flooding of multicast traffic by dynamically configuring Layer 2 interfaces so that multicast traffic is forwarded to only those interfaces associated with IP multicast address. In IPv6, MLD snooping performs a similar function. With MLD snooping, IPv6 multicast data is selectively forwarded to a list of ports intended to receive the data (instead of being flooded to all of the ports in a VLAN). This list is constructed by snooping IPv6 multicast control packets. Multicast VLAN Registration The Multicast VLAN Registration (MVR) protocol, like IGMP Snooping, allows a Layer 2 switch to listen to IGMP frames and forward the multicast traffic only to the receivers that request it. Unlike IGMP Snooping, MVR allows the switch to listen across different VLANs. MVR uses a dedicated VLAN, which is called the multicast VLAN, to forward multicast traffic over the Layer 2 network to the various VLANs that have multicast receivers as members. Layer 3 Multicast Features For information about configuring L3 multicast features, see "Managing IPv4 and IPv6 Multicast" on page 1137. Distance Vector Multicast Routing Protocol Distance Vector Multicast Routing Protocol (DVMRP) exchanges probe packets with all DVMRP-enabled routers, establishing two way neighboring relationships and building a neighbor table. It exchanges report packets and creates a unicast topology table, which is used to build the multicast routing table. This multicast route table is then used to route the multicast packets. 78 Switch Features