While connecting with putty (or any other ssh-client) it could happen, that the initial connection needs some time (up to a lot of time) to establish the connection to the target system.

The Problem could occure if the system is trying to look up the DNS entry of the connecting system. If you have not configured DNS in your environment or the system can’t be found it always takes some time till the connection is established.

To disable this problem the following line has to be added/uncommented in the SSHD-conf of the target system:

#UseDNS yes

to

UseDNS no