slow network on RHEL5

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Operating Systems Linux Red Hat slow network on RHEL5
# 1  
Old 09-09-2009
slow network on RHEL5

hey guys,

We have two Sun x2100 servers running RHEL5 in a test environment. Both servers are fresh OS installs and hooked up to the same network switch.

When ssh'ing to one server, there is a significant delay, while ssh'ing to the other server, the connection is almost instant. We are also having trouble getting some authentication test code to work correctly and believe it might be the cause of this delay.

On the "slow" server, I have replaced the cable, changed switch ports and ethernet ports on the server, but the delay is still there. Both servers are set to full duplex.

Just wondering if you guys could give me some other avenues to check. I'm guessing there's some configuration differences between server A and server B, but I'm not exactly sure what to look for.

Thanks in advance,
# 2  
Old 09-09-2009
Just a stab - Sometimes the slowness with SSH is that the remote sshd is trying to do a reverse DNS lookup to the client. Try commenting out any DNS servers in /etc/resolve.conf on the "slow" server and test. If that works, chances are. it's because your server is unable to communicate with the DNS server.
# 3  
Old 09-09-2009
Oh my, I think that did it!

On the slow server, /etc/resolv.conf had:
; generated by /sbin/dhclient-script

and on the fast server, /etc/resolv.conf was:
search localdomain

so I just removed the name server entry and replaced with the "search localdomain" and its much faster now.

I think I must have just put in a dummy IP when setting up the interface.

And to top it off, our authentication code works to the "slow" server now too.

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