[SOLVED] Some website are unreachable only on Ubuntu

[Bilanda]

Hello dear community,

I deployed a IPSec VPN without split tunneling. Everything works perfectly, but I have a strange issue.
Only for ubuntu users, some website are unreachable when they are connected to the Strongswan vpn.
Indeed, website like https://trello.com/ or https://duckduckgo.com/ can't be used, they always finish in time out.
But only on Ubuntu clients. No issue has been detected for MacOS/Windows/iOS/Android users.
I tried to update my own ubuntu kernel but nothing changed.
I tested with other web browser, but I got the same results.
Here are my laptop infos :
Ubuntu version : 20.04
Kernel : 5.8.0-48-generic
I saw nothing in any logs.
I'm on this issue since several weeks, but can't understand what's happening...
Do you have any idea on the reason of this issue ?
Tell me if you need more infos.
Thanks in advance !

[Bilanda]

Hello,
My bad, i misreaded the documentation.
It was indeed a MTU issue.
Setting MTU to 1360 solved my problem.
Best regards