ssh warning possible DNS spoofing remote host identification has changed

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@       WARNING: POSSIBLE DNS SPOOFING DETECTED!          @
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The ECDSA host key for hennah has changed,
and the key for the corresponding IP address xxx.xxx.xxx.xxx
is unknown. This could either mean that
DNS SPOOFING is happening or the IP address for the host
and its host key have changed at the same time.

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@    WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED!     @
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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
00:11:22:33:44:55:66:77:88:99:aa:bb:cc:dd:ee:ff.
Please contact your system administrator.
Add correct host key in /home/username/.ssh/known_hosts to get rid of this message.

Offending ECDSA key in /home/username/.ssh/known_hosts:9
ECDSA host key for hennah has changed and you have requested strict checking.
Host key verification failed.

http://security.stackexchange.com/questions/10532/ecdsa-keys-changed-ssh-insecure-now

 https://www.digitalocean.com/community/questions/how-can-i-get-rid-of-warning-remote-host-identification-has-changed

ssh-keygen -R [HOSTNAME]
ssh-keygen -R [ip_address]