since two days I am facing a really weird problem. I have receantly installed ubuntu server 14.04 LTS on a workstation. It has a fix IP address, which I can successfully ping from other computers in the network. But when I try to establish a ssh connection from a windows computer via putty I get some strange errors, which I cannot fix. The Problem is that putty takes a really long time trying to establish a connection. After about 10 seconds I get the following error:

Network error: Software caused connection abort

But when I click the Restart Session option a several times I can login in. But now comes the other problem. When the login appears on the putty console I type in the user, but it really takes a long time until I can type in the password to login.

This is what I already tried to solve that problem:

  • sshd: ALL in etc/hosts.allow
  • commented line pam_motd.so in etc/pam.d/login and etc/pam.d/sshd
  • configured the firewall with: sudo iptables -A INPUT -p tcp --dport ssh -j ACCEPT
  • already checked if ssh server is running and listening on port 22
  • UseDNS no in etc/ssh/sshd_config (EDIT)

FYI: The network which the server and the rest of our computers are, is the network of our university. I hope someone can help me with this. Thanks in regard :)

1 Answer 1


This sounds like it might be the same problem I have experienced. For me it turned out every time someone attempts to login through SSH, the SSH Daemon attempts to perform a reverse lookup. On some networks this causes trouble, and the user has to wait until the DNS lookup times out before he/she can continue.

Add the following line to /etc/ssh/sshd_config and see if it helps;

UseDNS no

Don't forget to restart the SSH Daemon;

service ssh restart
  • 1
    Thank you for your answer @RobinJ! I changed the config file the way you mentioned, but it did not solve the problem. Commented May 29, 2014 at 18:58
  • 1
    Have you tried this? superuser.com/a/441440/83658 Incidentially, have you tried another SSH client? It might not even be server-related :)
    – RobinJ
    Commented May 29, 2014 at 19:09
  • I already tried that too. None of the actions helped. Commented May 29, 2014 at 19:24
  • Don't know, then. But since you say it's on the university network, it's very possible that the university's network policy just doesn't allow it and that that's the problem.
    – RobinJ
    Commented May 30, 2014 at 9:36
  • Thank you very much @RobinJ. I will try to contact one the guys of the university. Commented May 30, 2014 at 10:17

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