in my company we have an old Dell running Windows 2000 server and ISA Server and it's our Internet gateway / firewall. Our current Internet connection is an ADSL and it's fairly slow (about 1 Mb/s in download, even slower in upload).

But now we have bought a cable connection from another provider, and we signed for a nominal 10 Mb/s.

Before switching to the new Internet connection I tested it for a while using a Windows 7 laptop, directly connected to the Ethernet cable provided by the ISP. It worked fine, and http://speedtest.net was giving me 8.5 Mb/s in download and around 5.5 in upload. So far, so good.

When I tried to connect our firewall to the new connection, I found that it works, but at a much lower speed than it should (about 1 Mb/s in download, 0.03 in upload!): it's actually slower than our ADSL...

So I set to do some tests; here's what I did and what I found out:

  • Windows 2000 server connected to the cable: slow;
  • Windows 7 laptop connected to the same cable, using the same network setup (static IP address, netmask, gateway, DNSs): fast;
  • Same laptop as above, booted a Kubuntu live distro, connected to the same cable and using the same network setup and the same network device: slow!

So I'm thinking maybe it's not a hardware problem but a configuration problem, but I'm not sure what to try. The only thing that came to my mind was the MTU size: Windows 7 reports a MTU of 1500, I don't know where to set it on Windows 2000 server but I set it so in Kubuntu and didn't make any difference.

Let me add that Speedtest.net was not my only benchmark, as I tried to download different files from the 'net (for example I used wget to to download the Firefox 6.0.2 package, always from the same URL) and the results were always the same.

What else could I try to troubleshoot the connection? Thank you very much for your help.


You may want to check to make sure the slow devices are negotiating the same speed/duplex settings as the windows 7 laptop. A duplex mismatch can cause network performance issues.

  • Checking the duplex settings is a good idea, thanks. I've found out how to check it in Linux: any hint on how to do the same in Windows Server 2000? Thanks again. – MacThePenguin Sep 11 '11 at 8:23
  • Forcing the network device on the Windows 2000 server to run at 10 Mb full duplex did the trick. Thanks. – MacThePenguin Sep 17 '11 at 13:31
  • 10 megabit full duplex will only allow you to download at approximately 1.25 Megabytes a second, just so you know. If you're being provided a higher than 10 Meg service by your provider you will find that your server's network card is slower than your internet connection. – Alex Berry Sep 16 '13 at 15:23

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