[CentOS] Slow login to system without internet connection

Hi Ljubomir, 

> But when I tried to login to my server, it was not instantenous, and I 
> think it was 15+, maybe even 30+ seconds (I forgot to time it) from 
> start of ssh command to password prompt. It is in-house connection, so 
> there is nothing to traceroute.


are you using an external DNS server that is reachable via the internet only?

If so, edit /etc/ssh/sshd_config and change this

  #UseDNS yes

to

  UseDNS no

Then restart sshd and see whether it still happens. sshd tries to look up its counterpart's host name using DNS in the default setting, and if DNS is not reachable it waits for the request to time out. 

Best regards, 

  Peter.