Reference Guide

Figure 111. Enhanced VLT
VLT Terminology
The following are 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 VLT peer switches. The backup link sends
configurable, periodic keep alive messages between the 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 the VLT peer devices, 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 you must use to
assign VLT global parameters.
• VLT peer device — One of a pair of devices that are connected with the special port channel known as the VLT
interconnect (VLTi).
VLT peer switches have independent management planes. A VLT interconnect between the VLT chassis maintains
synchronization of L2/L3 control planes across the two VLT peer switches. The VLT interconnect uses either 10G or 40G
user ports on the chassis.
A separate backup link maintains heartbeat messages across an out-of-band (OOB) management network. The backup
link ensures that node failure conditions are correctly detected and are not confused with failures of the VLT
interconnect. VLT ensures that local traffic on a chassis does not traverse the VLTi and takes the shortest path to the
destination via directly attached links.
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