Reference Guide

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 both IPv6/IPv4. 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 / IPv6 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.
NOTE: The peer routing and peer-routing-timeout is applicable for both IPv6/ IPv4.
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
vlt domain domain-id
2. Enable peer-routing.
VLT DOMAIN mode
peer-routing
3. Configure 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 is supported on the S4820T platform.
VLT Multicast Routing provides resiliency to multicast routed traffic 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 configured with a Spanned VLAN IP as their IIF are synced
between VLT peers. For multicast routes with a Spanned VLAN IIF, only OIFs configured with a Spanned
VLAN IP interface are synced between VLT peers.
The advantages of syncing the multicast routes between VLT peers are:
Virtual Link Trunking (VLT)
983