Have you encountered an issue where, despite successful pings, certain websites won’t load when using a VPN connection between MikroTik devices, such as WireGuard, with partial traffic routing? The reason could be incorrect MTU settings.
Problem:
When setting up a tunnel and routing only part of the traffic, some websites may fail to load, even though pings are successful.
Solution:
In my case, adjusting the MTU settings solved the issue. Thanks to a discussion on Habr, it became clear that MTU settings were causing the problem, and the correct adjustment restored stable connectivity.
Run the following commands on your MikroTik device to adjust MTU:
/ip firewall mangle
add action=change-mss chain=forward new-mss=clamp-to-pmtu out-interface=WireGuard protocol=tcp tcp-flags=synChange WireGuard to your VPN interface name.
Conclusion:
Setting the correct MTU is essential for a stable VPN connection on MikroTik. Proper MTU configuration can prevent website loading issues and optimize network performance.