Administrator Guide

Virtual Link Trunking (VLT)
Overview
In a traditional switched topology as shown below, spanning tree protocols (STPs) are used to block one or more links to prevent loops in
the network. Although loops are prevented, bandwidth of all links is not effectively utilized by the connected devices.
Figure 126. Traditional switched topology
VLT not only overcomes this caveat, but also provides a multipath to the connected devices. In the example shown below, the two
physical VLT peers appear as a single logical device to the connected devices. As the connected devices consider the VLT peers as a
single switch, VLT eliminates STP-blocked ports. However, the two VLT devices are independent Layer2/Layer3 (L2/L3) switches for
devices in the upstream network.
Figure 127. VLT providing multipath
VLT reduces the role of spanning tree protocols (STPs) by allowing link aggregation group (LAG) terminations on two separate
distribution or core switches and supporting a loop-free topology.
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