Dell C9000 series, Reference Manual

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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.
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.
Topics:
• back-up destination
• clear vlt statistics
• delay-restore
• lacp ungroup member-independent
• multicast peer-routing timeout
• peer-link port-channel
• peer-routing
• peer-routing-timeout
• primary-priority
• show vlt brief
• show vlt backup-link
• show vlt counters
• show vlt detail
• show vlt inconsistency
• show vlt mismatch
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