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Administrator Guide

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If you enable peer routing, a VLT node acts as a proxy gateway for its connected VLT peer as shown in the image below. Even
though the gateway address of the packet is different, Peer-1 routes the packet to its destination on behalf of Peer-2 to avoid
sub-optimal routing.
Figure 143. Packets with peer routing enabled
Benefits of Peer Routing
●
● Avoids sub-optimal routing
● Reduces latency by avoiding another hop in the traffic path.
● You can reduce the number of VLTi port channel members based on your specific design.
With peer routing, you need not configure VRRP for the participating VLANs. As both VLT nodes act as a gateway for its peer,
irrespective of the gateway IP address, the traffic flows upstream without any latency. There is no limitation for the number of
VLANS.
VLT Unicast Routing
VLT unicast routing is a type of VLT peer routing that locally routes unicast packets destined for the L3 endpoint of the VLT
peer. This method avoids sub-optimal routing. Peer-routing syncs the MAC addresses of both VLT peers and requires two local
DA entries in TCAM. If 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, the 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.
Virtual Link Trunking (VLT) 969