Moxa Technologies EM-1240-LX - Manual (Page 37)

EM-1240-LX User’s Manual Configuring EM-1240-LX
4-4
Destination NAT (DNAT)—changes the first destination packet IP address
MASQUERADE—a special form for SNAT. If one host can connect to the 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.
The following figure shows the IPTABLES hierarchy.
Incoming
Packets
Mangle Table
PREROUTING Chain
NAT Table
PREROUTING Chain
NAT Table
POSTROUTING Chain
Outgoing
Packets
Other Host
Packets
Mangle Table
FORWARD Chain
Filter Table
FORWARD Chain
Mangle Table
POSTROUTING Chain
Local Host
Packets
Mangle Table
INPUT Chain
Filter Table
INPUT Chain
Local
Process
Mangle Table
OUTPUT Chain
NAT Table
OUTPUT Chain
Filter Table
OUTPUT Chain