Slow SSH Response??

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

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