Dell Z9000 Configuration Manual page 831

Figure 113. 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 PIM-enabled 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 PIM-
enabled L3 VLANs for compatibility with IGMP.
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Virtual Link Trunking (VLT)