Hello, George Borisov a écrit :
Is there a way of forcing an MTU size for forwarded traffic on the firewall?
Yes, if the firewall is a router (not a bridge). You just set the desired MTU on the output interface.
I have tried playing with TCPMSS in iptables, but I haven't managed to get it to work.
Be aware that TCPMSS works only with TCP connections, not with other protocols like UDP or ICMP.