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Figure 146. Example of PIM-Sparse Mode on VLT
On each VLAN where the VLT peer nodes act as the rst hop or last hop routers, one of the VLT peer nodes is elected as the PIM
designated router. If you congured IGMP snooping along with PIM on the VLT VLANs, you must congure VLTi as the static multicast
router port on both VLT peer switches. This allows multicast trac that originates from the source that is connected to the VLT ports to
reach the PIM router which has downstream neighbors.
The VLT peer nodes can also act as normal PIM routers on Layer 3 ports and on VLANs that do not have any VLT port members. In
addition to being rst-hop or last -hop routers, the peer node can also act as an intermediate router.
To route trac to and from the multicast source and receiver that are connected to VLT ports, enable PIM-Sparse mode on the VLANs to
which the VLT ports belong using the ip pim sparse-mode command. If you congure IGMP snooping on these VLANs, the VLTi
must be congured as a static multicast router port on both VLT peers.
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.
To verify the PIM neighbors on the VLT VLAN and on the multicast port, use the show ip pim neighbor, show ip igmp
snooping mrouter, and show running config commands.
You cannot congure VLT peer nodes as rendezvous points, but you can connect PIM routers to VLT ports.
If the VLT node elected as the designated router fails, trac loss will occur until another VLT node is elected the designated router.
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Virtual Link Trunking (VLT)