I have a central Linux server (Red Hat version 6.5), and from this server I establish SSH sessions to other servers.

To one server the SSH login took around 5 seconds, while to all others it took less than one second.

Can someone help me to understand the reasons for this problem?

  • 1
    Check the dns configuration of the your remote slow server. – netmonk Apr 20 '16 at 8:13
  • What is your perceived login? Any particular banners/scripts to the slow server? I had one taking temperatures and stuff like that in /etc/update-motd.d for instance. – Rui F Ribeiro Apr 20 '16 at 9:59

Root cause of 98% similar problems is UseDNS parameter in /etc/ssh/sshd_config.
Switch its value to no and try again

  • 1
    And restart the service. – Jakuje Apr 20 '16 at 15:10
  1. Check that you can resolve the name of this server with 'nslookup'
  2. If not, switch off 'UseDNS' at /etc/ssh/sshd_config, or add your host to /etc/hosts

Should help.

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