Additionally the network where the receivers are

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Additionally, the network where the receivers are located is an Ethernet switchedLAN, in which two layer 2 multicast features, must be considered: IGMP Snoopingand Multicast VLAN.IGMPVersionThe first decision to be made is which version of IGMP will be implemented:IGMPv2 or IGMPv3.IGMPv3 should be used when source-specific multicast is required. This versionmatches adequately with PIM-SSM.If source-specific multicast is not required, then, IGMPv2 is simpler to implement andmaintain. Additionally, not all layer 2 switches support IGMPv3 snooping.IGMP QuerierIf there are multiple IPv4 gateways in a receivers’ subnet, two or more routers canbe enabled with IGMP.In any case, only one IGMP querier (Designated Router) can be active at any time.Anyway, there is no configuration necessary for this feature to work. If there is aneed to force one of these routers to become the querier, it has to be configured thesmallest IP address in the subnet.
HP Network Design Principles3 – 2Rev. 10.41IGMP SnoopingIGMP assumes that both queries and reports are received by all stations in thesubnet – it is a single Ethernet collision domain. So by default, Ethernet switches aredesigned to treat multicast traffic as if it were broadcast.To avoid multicast traffic to be flooded, Ethernet switches include the IGMPsnooping feature. It is recommended to implement everywhere.Multicast VLANWhen multiple VLANs are transported between a layer 2 switch and the IGMPquerier and there are receivers for a multicast group in more than one VLAN,multiple copies of the multicast traffic are forwarded by the querier.To avoid this, a Multicast VLAN can be configured in the Layer 2 switch. Thisfeature takes IGMP reports from a receiver’s VLAN and moves it to the Multicastvlan. In this way, the IGMP querier forwards a single multicast flow into this specialVLAN. The layer 2 switch, then, copies this traffic into each one of the receiver’sVLANs.There are two types of Multicast VLANs:1.port-based multicast VLANs2.subnet-based multicast VLANsBecause the end result is the same, any one of these options can be selected.Multicast Routing: PIMThe main advantage of PIM is that it uses the underlying IPv4 unicast routinginfrastructure to build the multicast distribution tree. This feature is called ReversePath Forwarding or RPF.When planning multicast routing the first step is to select the version of PIM to beused, also called PIM Mode: dense or sparse.PIM-DM or dense mode works well in LAN-only multicast applications and PIM-SM isbetter for large multi-site networks.PIM-SM also allows for the configuration of multiple multicast domains, which canbe useful for networks with many remote sites. In this last case, PIM-SM domains canbe connected with MSDP (Multicast Source Discovery Protocol). MSDP build anetwork of RPs and allows for traffic to be forwarded from one domain to anotherwhile still having local RPs.
Multicast DesignRev. 10.413 – 3If PIM-DM is chosen, there is need for further planning.

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