How to turn DNS off in sshd_config?

From: OttawaTrade (speediercoREMOVE_THIS_at_yahoo.com)
Date: 10/07/05 

Date: Thu, 6 Oct 2005 20:20:40 -0400

My server's DNS is very unstable, so many times, I can not ssh in, because
it keeps doing reverse DNS on the IP which sshs from.

Is there a way to turn it off?

Do I have to reboot it or there is some other way to take it into affect.

Thanks.