User`s manual

Moxa C Programmable RTU Controllers Managing Communications
4-6
The Moxa C programming RTU controller supports 3 types of IPTABLES table: Filter tables, NAT tables, and
Mangle tables:
A. Filter Table—includes three chains:
INPUT chain
OUTPUT chain
FORWARD chain
B. NAT Table—includes three chains:
PREROUTING chain—transfers the destination IP address (DNAT)
POSTROUTING chain—works after the routing process and before the Ethernet device process to transfer
the source IP address (SNAT)
OUTPUT chain—produces local packets
sub-tables
Source NAT (SNAT)—changes the first source packet IP address
Destination NAT (DNAT)—changes the first destination packet IP address
MASQUERADE—a special form for SNAT. If one host can connect to Internet, then other computers that
connect to this host can connect to the Internet when the computer does not have an actual IP address.
REDIRECT—a special form of DNAT that re-sends packets to a local host independent of the destination IP
address.
C. Mangle Table—includes two chains
PREROUTING chain—pre-processes packets before the routing process.
OUTPUT chain—processes packets after the routing process.
It has three extensions—TTL, MARK, TOS.