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Virtual Link Trunking (VLT)
Virtual link trunking (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.
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.
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Virtual Link Trunking (VLT)