Monitoring, Management & Location Tracking

Slow SSH Login Process


An SSH connection is slow to log in. The SSH connection to the server is made immediately, the server requests a password, but the time to get the first prompt is 30+ seconds.


When an SSH connection is made, the sshd process does a reverse DNS lookup on the client. If one of the DNS servers you have configured in /etc/resolv.conf is down or slow to respond, the SSH authentication process will be slow. All DNS servers configured will be queried and *all* must respond.


Test each DNS server for looking up the SSH client.


Remove any DNS server that is not responding.

An alternative solution is to edit the sshd configuration file and remove the DNS lookups during authentication.

# vi /etc/ssh/sshd_config

Find the line "#UseDNS yes" and uncomment it if necessary. Replace that line with:

UseDNS no

Save the file and restart sshd using:

# service sshd restart

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Last update:
‎06-29-2014 07:58 PM
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