MTU mismatch between GetIfEntry and netsh

Posted by ChrisJ on Stack Overflow See other posts from Stack Overflow or by ChrisJ
Published on 2010-05-07T17:48:32Z Indexed on 2010/05/08 0:18 UTC
Read the original article Hit count: 504

Filed under:

windows-vista

|

mtu

|

netsh

|

iphelper

I'm working on pseudo-transport layer software that runs over UDP, providing reliable connection-oriented transmission, as an alternative to TCP. In order to maximize network efficiency, we query the MTU of the "best" network adapter upon initialization.

MIB_IFROW row = {0};
row.dwIndex = dwBestIfIndex;

dwRes = GetIfEntry(&row);

Searching online I found that you can use the following netsh commands to query for this same value, from a command prompt (not a C++ API)

netsh interface ipv4 show interfaces
netsh interface ipv4 show subinterfaces

The troubling issue is that while row.dwMtu may be set to 1500, snooping the network traffic on the sending laptop shows that our packets are fragmented into 1300 byte packets. netsh also reports that the MTU is 1300.

Clearly the value reported by netsh command is the actual used values. Anyone know what API I can call to get the same values as netsh?

© Stack Overflow or respective owner

Related posts about windows-vista

I have Ubuntu alongside Windows Vista and I cannot reboot Windows Vista

as seen on Ask Ubuntu - Search for 'Ask Ubuntu'
I cannot get into Windows Vista .... I was working in Vista and then I restarted booted up Ubuntu and when I finished in Ubuntu I restarted this time in Vista and all I get is the microsoft box with the vertical stripes running interminably. I ran sudo update-grub this is the result of that command:… >>> More
Windows Vista language text service problem

as seen on Super User - Search for 'Super User'
Hi, All I'm using English version of Vista and having problems with using programs that display Russian characters somewhere. For example dictionaries doesn't work for me, since they display Russian character. Also I see just "magic" characters in text editor (notepad) when open a Russian text file… >>> More
Build One Application Version for Both Windows XP and Windows Vista

as seen on Internet.com - Search for 'Internet.com'
You don't have to compile two different versions to get applications that run correctly under both Windows XP and Windows Vista. >>> More
Q&A: Can you develop for the Windows Azure Platform using Windows XP?

as seen on Geeks with Blogs - Search for 'Geeks with Blogs'
This question has come up several times recently as we take several hundred UK developers through 6 Weeks of Windows Azure training (sorry – we are full). Short answer: In the main, yes Longer answer: The question is sparked by the requirements as stated on the Windows Azure SDK download page.… >>> More
Windows 8 / IIS 8 Concurrent Requests Limit

as seen on ASP.net Weblogs - Search for 'ASP.net Weblogs'
IIS 8 on Windows Server 2012 doesn’t have any fixed concurrent request limit, apart from whatever limit would be reached when resources are maxed. However, the client version of IIS 8, which is on Windows 8, does have a concurrent connection request limitation to limit high traffic production uses… >>> More

Related posts about mtu

MTU, DSL router and stalling TCP

as seen on Server Fault - Search for 'Server Fault'
I am discovering stalling TCP connection problem. The problem arises when I try to scp stuff from remote system from my home network. My home network is connected to internet via PPPoE (ADSL+) and everything works perfectly once working from my home network. The ADSL router has MTU set to 1492 but… >>> More
How to increase MTU size on Linux 2.6?

as seen on Server Fault - Search for 'Server Fault'
How to increase MTU size on Linux 2.6? Is such a thing possible? If yes, which files (in /etc or elsewhere) must one edit? >>> More
What should be the MTU Size for Windows Servers on the same Network

as seen on Server Fault - Search for 'Server Fault'
I have two windows servers on the same network, communicating to each other. What would be the best way to come up with the MTU setting? >>> More
TCP/UDP and ethernet MTU Fragmentation

as seen on Stack Overflow - Search for 'Stack Overflow'
I've read various sites and tutorials online but I am still confused. If the message is bigger than IP MTU, then send() returns the byte sent. What happens to the rest of the message? Am I to call send() again and attempt to send rest of the message? Or is that something IP layer should take care… >>> More
setup mtu automatically after system reboot

as seen on Super User - Search for 'Super User'
I have issues with slow internet and by changing mtu works fine for me. I use Ubuntu 9.10 64bit system. I have dynamic ip address setup All the time after system bootup, I need to do the following command to make mtu setting take effect. sudo ifconfig eth0 mtu 1492 Are there any way I can set… >>> More