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I am having problems with a Red Hat server 2.6.18.
The creation of a new TCP socket takes very long - once it is established it is fine. iptables and selinux are disabled - is there any other service which needs to be stopped?
Oddly enough I see the problem with Windows machines only.

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That sounds strange. Have you tried TCPDump to see what's really going on ? – Stephane Jul 13 '12 at 11:43
With which parameters should I use Tcpdump? I did not see my traffic as expected. The establishment of the traffic takes exactly 20 seconds. – weismat Jul 13 '12 at 13:07
up vote 2 down vote accepted

If you are using ssh, add the following to /etc/ssh/sshd_config

UseDNS no
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I am using simple tcp sockets on the application level - I have changed the sshd_config anyway with no effect. – weismat Jul 13 '12 at 13:11
You pointed me into the right direction - after adding the machines into the hosts file, the problem is gone. – weismat Jul 13 '12 at 13:48

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