MikroTik RouterOS v2.9 Reference Manual page 460

add chain=forward src-address=0.0.0.0/8 action=drop
add chain=forward dst-address=0.0.0.0/8 action=drop
add chain=forward src-address=127.0.0.0/8 action=drop
add chain=forward dst-address=127.0.0.0/8 action=drop
add chain=forward src-address=224.0.0.0/3 action=drop
add chain=forward dst-address=224.0.0.0/3 action=drop
Make jumps to new chains:
add chain=forward protocol=tcp action=jump jump-target=tcp
add chain=forward protocol=udp action=jump jump-target=udp
add chain=forward protocol=icmp action=jump jump-target=icmp
Create tcp chain and deny some tcp ports in it:
add chain=tcp protocol=tcp dst-port=69 action=drop \
comment="deny TFTP"
add chain=tcp protocol=tcp dst-port=111 action=drop \
comment="deny RPC portmapper"
add chain=tcp protocol=tcp dst-port=135 action=drop \
comment="deny RPC portmapper"
add chain=tcp protocol=tcp dst-port=137-139 action=drop \
comment="deny NBT"
add chain=tcp protocol=tcp dst-port=445 action=drop \
comment="deny cifs"
add chain=tcp protocol=tcp dst-port=2049 action=drop comment="deny NFS"
add chain=tcp protocol=tcp dst-port=12345-12346 action=drop comment="deny NetBus"
add chain=tcp protocol=tcp dst-port=20034 action=drop comment="deny NetBus"
add chain=tcp protocol=tcp dst-port=3133 action=drop comment="deny BackOriffice"
add chain=tcp protocol=tcp dst-port=67-68 action=drop comment="deny DHCP"
Deny udp ports in udp chain:
add chain=udp protocol=udp dst-port=69 action=drop comment="deny TFTP"
add chain=udp protocol=udp dst-port=111 action=drop comment="deny PRC portmapper"
add chain=udp protocol=udp dst-port=135 action=drop comment="deny PRC portmapper"
add chain=udp protocol=udp dst-port=137-139 action=drop comment="deny NBT"
add chain=udp protocol=udp dst-port=2049 action=drop comment="deny NFS"
add chain=udp protocol=udp dst-port=3133 action=drop comment="deny BackOriffice"
Allow only needed icmp codes in icmp chain:
add chain=icmp protocol=icmp icmp-options=0:0 action=accept \
comment="drop invalid connections"
add chain=icmp protocol=icmp icmp-options=3:0 action=accept \
comment="allow established connections"
add chain=icmp protocol=icmp icmp-options=3:1 action=accept \
comment="allow already established connections"
add chain=icmp protocol=icmp icmp-options=4:0 action=accept \
comment="allow source quench"
add chain=icmp protocol=icmp icmp-options=8:0 action=accept \
comment="allow echo request"
add chain=icmp protocol=icmp icmp-options=11:0 action=accept \
comment="allow time exceed"
add chain=icmp protocol=icmp icmp-options=12:0 action=accept \
comment="allow parameter bad"
add chain=icmp action=drop comment="deny all other types"
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