Reference Guide

Figure 127. 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.
Configure Virtual Link Trunking
VLT requires that you enable the feature and then configure the same VLT domain, backup link, and VLT interconnect on both
peer switches.
Important Points to Remember
● VLT port channel interfaces must be switch ports.
● If you include RSTP on the system, configure it before VLT. Refer to Configure Rapid Spanning Tree.
792
Virtual Link Trunking (VLT)