Reference Guide

952 | Virtual Link Trunking (VLT)
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Multiple VLT
A multiple VLT (mVLT) configuration allows two different VLT domains connected by a standard LACP
LAG to form a loop free Layer 2 topology in the aggregation layer. This configuration supports a
maximum of four (4) units, increasing the number of available ports and allowing for dual redundancy of
the VLT. The following figure shows how the core/aggregation port density in the Layer 2 topology is
increased using mVLT. For inter-VLAN routing and other Layer 3 routing, a separate Layer 3 router is
required.
VLT Terminology
The following are some key VLT terms.
Virtual link trunk (VLT) - The combined port channel between an attached device and the VLT peer
switches.
VLT backup link - The backup link monitors the vitality of a VLT peer switches. The backup link sends
configurable, periodic keep alive messages between VLT peer switches.
VLT interconnect (VLTi) - The link used to synchronize states between the VLT peer switches. Both ends
must be on 10G or 40G interfaces.
VLT domain - This domain includes both VLT peer devices, the VLT interconnect, and all of the port
channels in the VLT connected to the attached devices. It is also associated to the configuration mode that
must be used to assign VLT global parameters.