diff --git a/Readme.md b/Readme.md
index 672824b..694b30d 100644
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+++ b/Readme.md
@@ -36,3 +36,7 @@ defaults by pressing return
 1. Install wireguard client for your operating system (e.g. via package manager or Appstore)
 2. Import the client profile that was created during the server installation. It is located in `wireguard_profiles` subfolder
 as config file and as a qrcode png file to be scanned by mobile clients
+
+(!) under ubuntu, you have to enable tcp_mtu_probing e.g. by issuing 'echo 2 >
+/proc/sys/net/ipv4/tcp_mtu_probing' or by setting 'net.ipv4.tcp_mtu_probing = 2'
+/in /etc/sysctl.conf
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