[CentOS] Slow network

Filipe Brandenburger
Wed, 16 Sep 2009 15:33:56 -0000

Hi,

On Wed, Sep 16, 2009 at 11:25,  <centos at 911networks.com>
wrote:
> I plugged an Ubuntu laptop on the same cable and port with an Intel
> GigE, and it's about 8 to 10 times faster. So the problem is likely to
> be with the CentOS config.

How did you test that? Opening a web page? Downloading a big file?

> Any suggestion on how to track down the problem with speed.

First check if it's a DNS issue, check your /etc/resolv.conf to see if
both DNS servers there are correct, then check with "host" or
"nslookup" querying all of them to see if you get replies all of the
time.

If you have an iptables firewall running, you might want to try to
temporarily disable it to see if there is a difference.

If it's not DNS or Firewall, you might want to use "iperf" to
measure
the bandwidth available between that host and another host that works
well in your network. You can get "iperf" from the RPMforge repository
(http://wiki.centos.org/AdditionalResources/Repositories/RPMForge) or
from http://iperf.sourceforge.net/ (binaries for Linux and other
platforms should be available). From "iperf" you can really know if
there is an actual difference from your CentOS machine to your Ubuntu
laptop, with those numbers we might be able to give you better
suggestions on how to diagnose your problem.

HTH,
Filipe