How to prevent DNS reverse resolution IP ?

[jiawj]

I connected a pc server with ssh client, it prompted enter password too slow on my screen,
certainly it's not network bandwidth causation.
Then I noticed if no setting DNS (in file: /etc/resolv.conf), the issue that mentioned above occured, and I resolved it with setting DNS, but I wanna know how to solve it without DNS.
thx for any reply.

[crackers]

"Too slow" is not necessarily very descriptive - it's entirely relative to your experience.

After a quick run through of the man pages, it does not appear that you can avoid this. That's part of the security mechanism.