Dell PowerSwitch S4820T Configuration Guide for the S4820T System 9.100.0 - Page 899

Figure 134. PIM-Sparse Mode Support on VLT On each VLAN where the VLT peer nodes act as the first hop or last hop routers, one of the VLT peer nodes is elected as the PIM designated router. If you configured IGMP snooping along with PIM on the VLT VLANs, you must configure VLTi as the static multicast router port on both VLT peer switches. This ensures that for first hop routers, the packets from the source are redirected to the designated router (DR) if they are incorrectly hashed. In addition to being first-hop or last -hop routers, the peer node can also act as an intermediate router. On a VLT-enabled PIM router, if any PIM neighbor is reachable through a Spanned Layer 3 (L3) VLAN interface, this must be the only PIMenabled interface to reach that neighbor. A Spanned L3 VLAN is any L3 VLAN configured on both peers in a VLT domain. This does not apply to server-side L2 VLT ports because they do not connect to any PIM routers. These VLT ports can be members of multiple PIMenabled L3 VLANs for compatibility with IGMP. To route traffic to and from the multicast source and receiver, enable PIM on the L3 side connected to the PIM router using the ip pim sparse-mode command. Each VLT peer runs its own PIM protocol independently of other VLT peers. To ensure the PIM protocol states or multicast routing information base (MRIB) on the VLT peers are synced, if the incoming interface (IIF) and outgoing interface (OIF) are Spanned, the multicast route table is synced between the VLT peers. Virtual Link Trunking (VLT) 899