Command Line Reference Guide

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Virtual Link Trunking (VLT)

Virtual link trunking (VLT) is supported on the C-Series platform.

VLT allows physical links between two chassis to appear as a single virtual link to the network core.

VLT eliminates the requirement for Spanning Tree protocols by allowing link aggregation group

(LAG) terminations on two separate distribution or core switches, and by supporting a loop-free topol-

ogy. VLT provides Layer 2 multi-pathing, creating redundancy through increased bandwidth and

enabling multiple parallel paths between nodes and load-balancing traffic where alternative paths exist.

If the VLT peer-ship is already established, changing the System-MAC or Unit-Id does not cause VLT

peer-ship to go down.

Also, if the VLT peer-ship is already established and the VLT Unit-Id or System-MAC are configured

on both peers, then changing the CLI configurations on the VLT Unit-Id or System-MAC is rejected if

any of the following become TRUE:•

• After making the CLI configuration change, the VLT Unit-Id becomes identical on both peers.•

• After making the CLI configuration change, the VLT System-MAC do not match on both peers.

When the VLT peer-ship is already established, you can remove the VLT Unit-Id or System-MAC con-

figuration from either or both peers. However, removing configuration settings can cause the VLT

ports to go down if you configure the Unit-Id or System-MAC on only one of the VLT peers.

back-up destination

Configure the IPv4 address of the management interface on the remote VLT peer to be used as the

endpoint of the VLT backup link for sending out-of-band hello messages.

Syntax back-up destination {[ipv4–address] [interval seconds]}

Parameters

Note: When you launch the VLT link, the VLT peer-ship is not established if any of the

following is TRUE:

• The VLT System-MAC configured on both the VLT peers do not match.•

• The VLT Unit-Id configured on both the VLT peers are identical.•

• The VLT System-MAC or Unit-Id is configured only on one of the VLT peers.•

• The VLT domain ID is not the same on both peers.

ipv4–address

Enter the IPv4 address of the backup destination.

interval

seconds

Enter the keyword interval to specify the time interval to send hello

messages. The range is from 1 to 5 seconds. The default is 1 second.