Vlt Routing - Dell C9000 Series Networking Configuration Manual

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.
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.
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 configure 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 and you enable VLT Multicast Routing, multicast routes
are synced to the other peer for traffic forwarding to ensure minimal traffic loss. If you did not enable VLT
Multicast Routing, traffic loss occurs until the other VLT peer is selected as the DR.

VLT Routing

VLT unicast and multicast routing is supported on the switch.
Layer 2 protocols from the ToR to the server are intra-rack and inter-rack. No spanning tree is required, but
interoperability with spanning trees at the aggregation layer is supported. Communication is active-active,
with no blocked links. MAC tables are synchronized between VLT nodes for bridging and you can enable
IGMP snooping.
Because VLT ports are Layer 2 ports and not IP interfaces, VLT Unicast and VLT Multicast routing protocols do
not operate directly on VLT ports. You must add the VLT ports as a member of one or more VLANs and assign
IP addresses to these VLANs. VLT Unicast and VLT Multicast routing protocols require VLAN IP interfaces for
operation. Protocols such as BGP, ISIS, OSPF, and PIM are compatible with VLT Unicast Routing and VLT
Multicast Routing.
Virtual Link Trunking (VLT) 1176