Hi all,

I have the following problem as I ssh from our server to client server, please give me a hand to see how to solve it, or is there any tool/method to scan the server, thanks :

[root@localhost ~]# ssh 210.147.87.155
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
@ 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 the RSA host key has just been changed.
The fingerprint for the RSA key sent by the remote host is
bd:95:8d:91:33:f7:c1:dd:96:29:47:b8:13:95:06:a6.
Please contact your system administrator.
Add correct host key in /root/.ssh/known_hosts to get rid of this message.
Offending key in /root/.ssh/known_hosts:21
RSA host key for 210.147.87.155 has changed and you have requested strict checking.
Host key verification failed.
[root@localhost ~]#

As shown in your post, the targets rsa-key has changed. Either you or someone else has installed a new system on the target host or the ip is used by another computer.

If you are shure, that you are connecting the right system, than delete the line, starting with 210.147.87.155 in ~/.ssh/known_hosts.