#.#.#.#_#.#.#.#/32-#.#.#.#_#.#.#.#/32: Tunnel LastAlert: Received Delete for IPSec-S
This message is generated when the remote peer deletes the Security Association. A VPN Tunnel idle timeout would generate such a message.
This is a known issue in NSX 6.4.0 and is resolved in NSX 6.4.1. This issue is documented in the NSX 6.4.1 release notes as follows:
Source: VMware NSX for vSphere 6.4.1 Release Notes
To resolve the issue, upgrade the environment, including NSX Edges, from version 6.4.0 to version 6.4.1.
Workaround: