Cannot change tunnel MTU anymore.

[kamil445]

Hi,

I reinstalled Windows, old installation had only updates to 2021, now system is up to date but becuse of this, now i cannot change tunnel interface MTU, default is 1280, always i changed to 1480 (IPv4 MTU = 1500, IPv6 = 1500-20). I used this command that worked well on Windows 7 and Windows 10 updated only with 2021 updates:

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netsh interface ipv6 set subinterface IP6Tunnel mtu=1480 store=persistent
I can only input 1280, nothing less, nothing more.

There is any way to change MTU on updated system ? maybe PowerShell way ? or i need to install windows updated only with 2021 updates.

I do some research and found this, i am not only person who have this issue:

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https://serverfault.com/questions/1093908/windows-mtu-can-no-longer-be-set-higher-than-1500-bytes

https://www.elevenforum.com/t/setting-jumbo-packets-does-not-change-the-mtu.3505/
For someone, reinstall was the solution but i have installation ISO updated to 2023 and i probably have integrated "bad" updates, so reinstall will do nothing...

Any ideas ?
Thanks!