Administrator Guide

Virtual Link Trunking (VLT)
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 topology. VLT provides Layer 2 multipathing, creating redundancy through
increased bandwidth and enabling multiple parallel paths between nodes and load-balancing traffic where alternative paths exist.
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.
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 configuration 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.
Topics:
• back-up destination
• clear vlt statistics
• lacp ungroup member-independent
• peer-link port-channel
• show vlt backup-link
• show vlt brief
• show vlt detail
• show vlt mismatch
• show vlt role
• show vlt statistics
• stack-unit iom-mode
• system-mac
• unit-id
• vlt domain
• vlt-peer-lag port-channel
back-up destination
Configure the IPv4 or IPv6 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] | [ipv6 ipv6–address] [interval
seconds]}
Parameters
ipv4–address Enter the IPv4 address of the backup destination.
ipv6 Enter the keyword ipv6 then an IPv6 address in the X:X:X:X::X format.
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