Users Guide

VLT Unicast Routing
VLT unicast routing locally routes packets destined for the L3 endpoint of the VLT peer. This method
avoids suboptimal routing.
In VLT unicast 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 both IPv4 and IPv6. 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 or 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 commands are supported on both IPv4
and IPv6 to enable L3 VLT peer routing and configure the delay after which peer routing is disabled.
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 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
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Virtual Link Trunking (VLT)