SSH protocol and user are configured on the Router but when Putty is used to Login the session is terminated before the login screen can appear with server sending disconnect error message. See the Attachement for the error message.
The alarm information from Putty usually leads one to beleive that there is something wrong with the version of ssh being used but it is not so.
To Resolve the problem issue the following command on the Router:
rsa local-key-pair create
After the the rsa local key-pair has been created user will be sucessfuly presented with the login screen and ssh login will succed provided that the username and password are correct.
This error message occures because there is no local-key-pair for encryption on the router and the ssh session is closed before the login screen is presented to the user.
A quick way to check the rsa local-key-pair on the router is to isseu the command:
display rsa local-key-pair public
If there is no output to the above command then no rsa local-key-pair exists on the router.