WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED!

When connecting to ssh, the following prompt appears in the terminal:

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@    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 RSA key sent by the remote host is
SHA256:QMBDB0OsAOFhFfTr/OfF1o1b4CYFqO57jKq/Wh9IZFk.
Please contact your system administrator.
Add correct host key in /home/user20051/.ssh/known_hosts to get rid of this message.
Offending RSA key in /home/user20051/.ssh/known_hosts:2
  remove with:
  ssh-keygen -f "/home/user20051/.ssh/known_hosts" -R "10.21.60.100"
RSA host key for 10.21.60.100 has changed and you have requested strict checking.
Host key verification failed.
lost connection
we should use command to clear connected IP:

ssh-keygen -R XX.XX.XX.XX 

XX.XX.XX.XX is the network segment IP of the previous connection

 Reason for the problem：

此报错是由于远程的主机的公钥发生了变化导致的。 
ssh服务是通过公钥和私钥来进行连接的，它会把每个曾经访问过计算机或服务器的公钥（public key），记录在~/.ssh/known_hosts 中，当下次访问曾经访问过的计算机或服务器时，ssh就会核对公钥，如果和上次记录的不同，OpenSSH会发出警告。
 

reference：问题解决——SSH时出现WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED!_口袋里のInit的博客-优快云博客