hi,

yesterday i tried to get connect to a system in my n/w through ssh.
and i got access. but today it showing me following message

#ssh 10.10.10.69
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
@ 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
3d:1b:02:9e:b2:b8:f0:f7:c6:4f:94:96:f6:e3:c0:d1.
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:8
RSA host key for 10.10.10.69 has changed and you have requested strict checking.Host key verification failed.

what should i do??

You get this because something has changed, network-wise. One of the systems (either the host or client), has a new NIC card, new IP address, etc. Usually happens if you get a new DHCP address on your workstation when you boot up.

You can edit the $HOME/.ssh/known_hosts file, and remove the entry you see in there for 10.10.10.69 (hope that's not a real server address you put in your message...). Then connect again. It'll verify the info, and connect. If the address changes again, you'll get this message again.