I have noticed that after upgrading my laptop (not sure if this is the reason) to 18.04 Ubuntu, I have not been able to ssh to an institute server although I'm able to on the same internet network from a desktop computer.

When "ssh -v" is applied the following is the result before timing out:

OpenSSH_7.6p1 Ubuntu-4ubuntu0.1, OpenSSL 1.0.2n 7 Dec 2017 
debug1: Reading configuration data /etc/ssh/ssh_config 
debug1: /etc/ssh/ssh_config line 19: Applying options for * 
debug1: Connecting to xxx.xxxxx.xxx.edu [128.118.xxx.xxx] port 22.

I have tried deleting the known_hosts file, as it was one of the suggestions on the internet. However, it did not resolve this issue. Any tips that might help fix the problem are welcome. Thanks!

  • 'institute server' - is it on the same network? what happens when you try? Can you ping the remote server directly? – Thomas Ward Dec 12 '18 at 20:35
  • I am able to ping the remote server. – Sameeresque Dec 12 '18 at 20:38
  • Yes, the institute server is on the same network – Sameeresque Dec 12 '18 at 20:40
  • The institute had made some recent changes to the firewall and had recommended the use of a VPN. I have installed and used that VPN, the VPN service connects successfully, but when I try Sshing, this error is returned: ssh: Could not resolve hostname xxx.xxxx.xxx.edu: Name or service not known. I am also not able to browse the internet – Sameeresque Dec 12 '18 at 20:47
  • If you are already on the same network, there should be no need to connect through VPN. VPN is typically used for connections from outside to the destination network. Maybe does "ssh -v" help to debug the issue? Do you use private+public keys for authentication or password? – Oliver R. Dec 12 '18 at 20:54

There're two things to consider:

  1. If the server hosts (the Institute) now say you should use a VPN to access the system, then it's quite likely that they are disallowing access from the rest of the same shared network and requiring you to use the VPN to pass traffic to the server first. In this case, you have no choice but to use the VPN.

    However, given that you couldn't resolve the host name, the second part to consider is...

  2. There is no DNS server on the VPN connection that can handle resolving the hostname that you're entering.

    This means the people running the VPN need to set up a DNS server on the VPN and specify it in the VPN connection to resolve the hostname to an IP address.

    In the interim you can use the direct IP address for the server for your connections, and if you're over the VPN that should give you access to the server.

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