I use putty to connect to my application servers, but many times I face issue in connecting to the server via hostname. The error message says, 'Unable to open connection to my_hostname Host does not exist'. Sometimes, on restarting the system, the issue gets resolved automatically but many times even on restarting the same problem occurs. This problem does not occur when connecting to the server via IP address. But for many servers I do not have the IP addresses, which creates a problem. I have gone through many such related articles and posts but none helped me out. I am using a company laptop and as of now formatting the system would be a challenge for me. If anybody could help me diagnosing and fixing the issue, it would be great.
It is a DNS problem. If the problem occurs from inside the company network, then you may be getting incorrect nameserver information when your laptop gets an address from the DHCP server. If it is from outside the company network, then it is a problem with DNS propogation from inside the network to the public DNS servers. If the problem only occurs from outside the company network, that is out of your hands. The solution is to find out the IP addresses and add them to your computer's hostfile. In windows 10 it is located at C:\Windows\System32\drivers\etc\hosts You can make entries for those hostnames and point them to the proper IP addresses, and you are good to go unless they change those IP addresses in the future.