Windows xp set mtu size netsh

It affects all of the computers on our local network Ethernet, not wireless , all of which are running Windows XP. It has been suggested to me that it might be to do with the MTU used on network traffic.

If I try and ping something on the outside like Google, I can't get anything through bigger than which is with the header. I've tried no end of alternative values: the most obvious correct value seems to be , but I've also tried , , , etc. When I reboot the computer to make the change take effect, it seems to work for a few minutes hard to tell for certain since it's always random rather than consistent but it never lasts long.

Initially, when I was trying as a value, after a few minutes of working fine, the results of the Ping Test would decrease by 28 bytes - suddenly I'd find that I could only get a package of bytes through to Google. If I updated the MTU registry setting to , when I rebooted and waited a few minutes, it'd then be , then , etc.

Other computers on the network remained unaffected still at and removing the MTU setting from the registry would restore things to normal and still broken. The thing that I find the hardest about diagnosing all this is that it's very hard to tell if I'm even playing with the correct registry setting.

Also, if anybody has any ideas how to tell why the MTU keeps dropping by 28, that would be useful too e. Finally, if anybody can tell me definitively how to tell what MTU setting I should be trying to use, that would be great! From an elevated command prompt:. For that you can:.

This leaves less space available in the packet:. Now an ICMP ping packet has an 8-byte header 1 byte type , 1 byte code , 2 byte checksum , 4 byte additional data :. That's where the "missing" 28 bytes is - it's the size of the headers required to send a ping packet. When you send a ping packet, you can specify how much extra payload data you'd like to include. In this case, if you include all bytes:. Then the resulting ethernet packet will be full to the gills.

Every last byte of the byte packet will be filled:. The -f flag means do not fragment. Now when you try to send a packet that doesn't fit on the network you get the error:. If anywhere along the line a packet needed to be fragmented, the network actually sends an ICMP packet telling you that a fragmentation happened. Your machine gets this ICMP packet, is told what the largest size was, and is supposed to stop sending packets too big.

Unfortunately most firewalls block these "Path MTU discovery" ICMP packets, so your machine never realizes the packets are being fragmented or worse: dropped because they couldn't be fragmented. That's what causes web-server to not work. And the web-server's firewalls are misconfigured, blocking ICMP packets. So the web-server doesn't realize you never got the packet. I then added the following registry keys:. I tried several values for the MTU entry rebooting each time.

Download Microsoft Edge More info. Contents Exit focus mode. Please rate your experience Yes No. Any additional feedback? Note Use the methods in this article to edit the registry to modify the MTU size settings. Important This section, method, or task contains steps that tell you how to modify the registry.

In this article. This method affects packets sent to all destinations and may significantly affect the performance, depending on the MTU size that you set. To set the MTU size for the network interface, follow these steps:. For more information, click the following article number to view the article in the Microsoft Knowledge Base:. Need more help? Expand your skills. Get new features first. Was this information helpful? Yes No. Thank you!

Any more feedback? The more you tell us the more we can help. Can you help us improve? Resolved my issue. Clear instructions. Easy to follow. No jargon. Pictures helped. Didn't match my screen.