Firewall / Mangle / PREROUTING

RouterOS General
1

Today, I have the following rule in iptables, how you could apply the same using RouterOS, version 5.25. I appreciate the help.

iptables -t mangle -I PREROUTING  -i eth0 -p tcp --tcp-flags SYN,RST SYN -m tcpmss --mss 1200:1546 -j TCPMSS --set-mss 1400

Regards,
Daniel.

2

to do this hack use:
/ip firewall mangle
add action=change-mss chain=forward disabled=no new-mss=1400 passthrough=yes
protocol=tcp tcp-flags=syn tcp-mss=1201-1546
To have this correct setup, use this:

/ip firewall mangle
add action=change-mss chain=forward disabled=no new-mss=1400 passthrough=yes
protocol=tcp tcp-flags=syn tcp-mss=1401-65535