David Fowler troubleshoots an issue:
Checking the logs on the secondary, it was littered with ‘Database Mirroring login attempt failed with error: ‘Connection handshake failed. An OS call failed: (80090302) 0x80090302(The function requested is not supported).’ messages. The primary server wasn’t able to authenticate with the secondary, but why? Everything looked ok as far as I could see.
Click through for the fruits of David’s labor.