Swap/change host entries in ~/.ssh/known_hosts so that an incorrect IP address is listed for your host:
From:
192.168.0.10 ecdsa-sha2-nistp256 AAAAE2...kFr3pqkY=
192.168.0.20 ecdsa-sha2-nistp256 AAAAE2...A82zdls0=
To:
192.168.0.20 ecdsa-sha2-nistp256 AAAAE2...kFr3pqkY=
192.168.0.10 ecdsa-sha2-nistp256 AAAAE2...A82zdls0=
(Note that the IP addresses has been swapped)
Will then give you:
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
@ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! @
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!
Someone could be eavesdropping on you right now (man-in-the-middle attack)!
It is also possible that a host key has just been changed.
The fingerprint for the ECDSA key sent by the remote host is
You get this warning when the key offered by the client pair with the key on the server, but the IP address differs. The assumption then is that you're the subject of a man-in-the-middle attack and a warning is issued.