This is just a personal reminder, however maybe some can find this info useful.
Issue: While I was making ssh connections to some Linux server, I noticed a extreme slowness for the server to accept the connection, some times from 20 to 45 seconds.
To fix it:
This problem was due to DNS reverse lookups being performed by SSH server. So, it’s just a matter of changing this value inside your ssh configuration file. In this case I was working with SLES 10 sp 3
servername:~ # cat /etc/ssh/sshd_config | grep -i dns #UseDNS yes servername:~ #
Changed the option UseDNS from yes to no and reload SSH daemon:
servername:~ # cat /etc/ssh/sshd_config | grep -i dns UseDNS no