Comprehensive and Detailed 250 to 350 words of Explanation From VMware Cloud Foundation (VCF) documents:
InVMware Cloud Foundation (VCF), theNSX Manageruses the SFTP protocol to securely transfer configuration backups to an external repository. SFTP is built on top of the SSH protocol, which relies on a "Trust on First Use" (TOFU) model for verifying the identity of the remote host.
When an NSX Manager first connects to an SFTP server, it retrieves the server'sSSH Public Key Fingerprintand stores it in its local known_hosts equivalent database. This fingerprint ensures that future connections are made to the same, verified server, preventing man-in-the-middle attacks.
The error"Host KEY Verification Failed"occurs when the administrator changes the SFTP server (or if the SFTP server's OS was reinstalled/keys regenerated). Even if the IP address remains the same, the new server presents a different SSH fingerprint than the one currently cached in the NSX Manager configuration. Because the signatures do not match, the NSX Manager aborts the connection for security reasons.
To resolve this issue, the administrator mustUpdate the SSH fingerprint(Option B) within the NSX Manager backup settings. This involves:
Retrieving the new fingerprint from the SFTP server (e.g., via ssh-keyscan).
Navigating to System > Lifecycle > Backup & Restore in the NSX Manager.
Editing the File Server configuration and pasting the new fingerprint into the appropriate field.
Option A is incorrect as it does not address the SSH protocol handshake failure. Option C is incorrect because SFTP/SSH uses fingerprints, not SSL/TLS certificates. Option D is irrelevant as it changes the source/destination of the connection but does not fix the underlying trust mismatch. Therefore, updating the fingerprint is the verified operational step to restore the automated backup workflow in VCF.
