Port mapping is to map the internal network (LAN) IP address of a host to a public network (WAN) IP address. When a user accesses a port of the host that provides the mapped port, the server transfers the request to the local LAN to provide this The host of a specific service; the port mapping function can also map multiple ports of a machine with an external network IP address to different ports on different machines in the internal network. Port mapping is divided into dynamic and static.
The following is the experimental goal of this topology map
: Convert the 80 port of the server port 192.168.100.111 to the 8080 port of 12.0.0.5, and enable it on the port.
Allowing the external network to access port 8080 of 12.0.0.5 will map to port 80 of 192.168.100.111, and directly access 192.168.100.111. 
1: Check the details of the Linux network card and
bind the network card vmnet1 
2: Set the IP subnet mask on windows7 Code gateway
network card is set to vmnet2
3: Configure router R3
to enter the global mode
, set the IP of port f0/0 and open the IP of
port f0/1 and open
the port 80 to convert the server port 192.168.100.111 to port 8080 of 12.0.0.5
(this way to access 12.0.0.5's port 80) Port 8080 will be mapped to port 80 of 192.168.100.111)
enable NAT on the interface
end exit to privileged mode open port detection debug ip nat 
open the browser on windows and enter http://12.0.0.5:8080/
to access linux The lamp built
in can see the details of address translation in router R3