Answer by Garry Harthill for Simulate the remote host identification warning

One way is to change the keys on the remote server so when they are verified against the entry in your known_hosts file it won't match and give you that message.

Regenerate your host keys on the remote server with something like:

ssh-keygen -f /etc/ssh/ssh_host_rsa_key -N '' -t rsa
ssh-keygen -f /etc/ssh/ssh_host_dsa_key -N '' -t dsa
ssh-keygen -f /etc/ssh/ssh_host_ecdsa_key -N '' -t ecdsa -b 521

Then restart the SSH server.

You could also edit the known_hosts file on the client to contain an entry for another server but with the hostname of the remote server you want to get the message with.