When a VLT node is reloaded, all interfaces including VLT port-channel interfaces go down. Top-of-Rack (ToR) devices connected at the other end of the VLT port-channel interfaces could take a considerable amount of time to detect the interface status change and switch the traffic towards the other active VLT node. Using LACP PDUs, the graceful LACP feature enables VLT nodes to inform ToR devices before taking down the member ports of its VLT port-channel interfaces. Thus, the graceful LACP feature 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.