Server Fault is a question and answer site for system and network administrators. It's 100% free, no registration required.

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

I have two servers.

The ping respond time of them are both about 210 ms.

But the ssh respond time is quite different. One is fast(~200ms) while another is quite slow(~1s). CPU and memory of these two servers are different. But CPU usage are both 0% when I'm testing.

What can be the root cause of this huge difference of ssh respond time?

share|improve this question
Define better what you see as response time. Is it during login, or after having logged in and typing in the shell? – Joris Apr 10 '11 at 8:13
It's the response of my typing in the shell. Thanks. – Ricky Apr 10 '11 at 11:03

There's a chance that it's routing. It's called asynchronous routing if a network takes very different paths in and out of their network. Since you have logins at both ends run traceroute (use mtr) to check any obvious differences. Paste them here if you need a hand interpreting them.

I didn't ask if you are just referring to response times at login and not during use. Disable reverse lookups at login with 'UseDNS no' in sshd_config for general use and testing.


When you start your SSH client use ssh -c blowfish user@host. This should speed up the slower connection using faster encryption.

share|improve this answer
Thanks for the reply. The tracert for both hosts are similar in regards of hops and the delay. Setting "UseDNS no" seems having some help. – Ricky Apr 10 '11 at 11:15

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.