Users Guide

VLT unicast, VLAN conguration must be symmetrical on both peers. You cannot congure the same VLAN as Layer 2 on one node and as
Layer 3 on the other node. Conguration 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 or IPv6 address congured 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.
NOTE: The peer-routing and peer-routing-timeout commands are supported on both IPv4 and IPv6 to enable L3 VLT
peer routing and congure the delay after which peer routing is disabled.
Conguring
VLT Unicast
To enable and congure VLT unicast, follow these steps.
1 Enable VLT on a switch, then congure a VLT domain and enter VLT-domain conguration mode.
CONFIGURATION mode
vlt domain domain-id
2 Enable peer-routing.
VLT DOMAIN mode
peer-routing
3 Congure the peer-routing timeout.
VLT DOMAIN mode
peer-routing—timeout value
value: Specify a value (in seconds) from 1 to 65535.
VLT Multicast Routing
VLT Multicast Routing provides resiliency to multicast routed trac during the multicast routing protocol convergence period after a VLT
link or VLT peer fails using the least intrusive method (PIM) and does not alter current protocol behavior.
Unlike VLT Unicast Routing, a normal multicast routing protocol does not exchange multicast routes between VLT peers. When you enable
VLT Multicast Routing, the multicast routing table is synced between the VLT peers. Only multicast routes congured with a Spanned
VLAN IP as their IIF are synced between VLT peers. For multicast routes with a Spanned VLAN IIF, only OIFs congured with a Spanned
VLAN IP interface are synced between VLT peers.
The advantages of syncing the multicast routes between VLT peers are:
• VLT resiliency — After a VLT link or peer failure, if the trac hashes to the VLT peer, the trac continues to be routed using multicast
until the PIM protocol detects the failure and adjusts the multicast distribution tree.
• Optimal routing — The VLT peer that receives the incoming trac can directly route trac to all downstream routers connected on
VLT ports.
• Optimal VLTi forwarding — Only one copy of the incoming multicast trac is sent on the VLTi for routing or forwarding to any orphan
ports, rather than forwarding all the routed copies.
Important Points to Remember
• You cannot congure a VLT node as a rendezvous point (RP), but any PIM-SM compatible VLT node can serve as a designated router
(DR).
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Virtual Link Trunking (VLT)