/ip firewall nat chain=dstnat action=netmap to-addresses=192.168.1.2 to-ports=80 protocol=tcp packet-mark=1
/ip firewall nat chain=srcnat action=src-nat to-addresses=192.168.1.1 packet-mark=1
/ip firewall mangle chain=prerouting action=mark-packet new-packet-mark=1 passthrough=yes protocol=tcp src-address=192.168.1.0/24 dst-address=1.1.1.1 dst-port=81