Reference Guide

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 routing is supported on the Z9000 platform.
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.
Spanned VLANs
Any VLAN configured on both VLT peer nodes is referred to as a Spanned VLAN. The VLT Interconnect (VLTi) port is
automatically added as a member of the Spanned VLAN. As a result, any adjacent router connected to at least one VLT
node on a Spanned VLAN subnet is directly reachable from both VLT peer nodes at the routing level.
VLT Unicast Routing
VLT unicast routing is supported on the Z9000 platform.
VLT unicast routing locally routes packets destined for the L3 endpoint of the VLT peer. This method avoids suboptimal
routing. Peer-routing syncs the MAC addresses of both VLT peers and requires two local DA entries in TCAM. In case a
VLT node is down, a timer that allows you to configure the amount of time needed for peer recovery provides resiliency.
You can enable VLT unicast across multiple configurations using VLT links. You can enable ECMP on VLT nodes using
VLT unicast.
VLT unicast routing is supported on IPv4 only. To enable VLT unicast routing, both VLT peers must be in L3 mode. Static
route and routing protocols such as RIP, OSPF, ISIS, and BGP are supported. However, point-to-point configuration is
not supported. To enable VLT unicast, VLAN configuration must be symmetrical on both peers. You cannot configure the
same VLAN as Layer 2 on one node and as Layer 3 on the other node. Configuration mismatches are logged in the syslog
and display in the show vlt mismatch command output.
If you enable VLT unicast routing, the following actions occur:
• L3 routing is enabled on any new IP address configured for a VLAN interface that is up.
• L3 routing is enabled on any VLAN with an admin state of up.
NOTE: If the CAM is full, do not enable peer-routing.
Configuring VLT Unicast
To enable and configure VLT unicast, follow these steps.
1. Enable VLT on a switch, then configure a VLT domain and enter VLT-domain configuration mode.
CONFIGURATION mode
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