Windows 2008R2 MTU reverts to default

[Dick Visser]

Hi


I'm trying to debug a connectivity issue on a Windows 2008R2 system,
and I'd like to carry out some tests with different MTUs.
According to the docs at
http://technet.microsoft.com/en-us/library/cc753156(v=ws.10).aspx#BKMK_setinterface
I issue this command:

C:\Windows\system32>netsh interface ipv6 set interface "Local Area
Connection" mtu=1400
Ok.

I then see:

C:\Windows\system32>netsh interface ipv6 show interfaces

Idx     Met         MTU          State                Name
---  ----------  ----------  ------------  ---------------------------
  1          50  4294967295  connected     Loopback Pseudo-Interface 1
 10          10        1400  connected     Local Area Connection


This works for a while, but after a minute or so it changes back to the default:

C:\Windows\system32>netsh interface ipv6 show interfaces

Idx     Met         MTU          State                Name
---  ----------  ----------  ------------  ---------------------------
  1          50  4294967295  connected     Loopback Pseudo-Interface 1
 10          10        1500  connected     Local Area Connection


The default netsh behavior should be to save it persistently, but upon
reboot the MTU is always 1500.


Any ideas what might be causing this?


I just tried out a Windows 7 machine and that seem to remember what
it's being told with netsh.


Thanks!!


-- 
Dick Visser
System & Networking Engineer
TERENA Secretariat
Singel 468 D, 1017 AW Amsterdam
The Netherlands