Connectivity Guide

● Traffic with an unknown destination MAC address, multicast, or broadcast traffic can cause flooding across the VLTi.
● MAC, ARP, IPv6 neighbors that are learned over VLANs on VLT peer nodes synchronize using VLTi.
● LLDP, flow control, port monitoring, and jumbo frame features are supported on a VLTi.
Graceful LACP with VLT
When a VLT node is reloaded, all its interfaces including VLT port-channel interfaces go down. Top-of-rack (ToR) devices
connected at the other end of the VLT port-channel interfaces take a considerable amount of time to detect the interface
status change and switch the traffic towards the other active VLT node. This causes traffic loss for a long time interval. Using
LACP PDUs, the graceful LACP feature allows VLT nodes to inform ToR devices ahead of taking down the member ports of its
VLT port-channel interfaces. This enables the ToR devices to switch the traffic to the other active VLT node.
Graceful LACP is supported in these scenarios:
● When a VLT node is reloaded.
● When the secondary VLT node detects that the VLTi link is down but the heartbeat is functional.
Graceful LACP is enabled by default and you cannot disable it.
The following shows the normal behavior of a VLT setup where data flows through the optimal path to its destination.
The following shows a scenario where VLT Peer A is being reloaded or going down. Until LACP convergence happens, ToR 1
continues to forward traffic to VLT Peer A resulting in traffic loss for a longer time interval.
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Virtual Link Trunking