Chapter 11 Network Address Translation (NAT)
VMG5313-B10A/-B30A Series User’s Guide
182
NAT
In the simplest form, NAT changes the source IP address in a packet received from a subscriber
(the inside local address) to another (the inside global address) before forwarding the packet to the
WAN side. When the response comes back, NAT translates the destination address (the inside
global address) back to the inside local address before forwarding it to the original inside host.
Port Forwarding
A port forwarding set is a list of inside (behind NAT on the LAN) servers, for example, web or FTP,
that you can make visible to the outside world even though NAT makes your whole inside network
appear as a single computer to the outside world.
Finding Out More
See
for advanced technical information on NAT.
11.2 The Port Forwarding Screen
Use the
Port Forwarding
screen to forward incoming service requests to the server(s) on your
local network.
You may enter a single port number or a range of port numbers to be forwarded, and the local IP
address of the desired server. The port number identifies a service; for example, web service is on
port 80 and FTP on port 21. In some cases, such as for unknown services or where one server can
support more than one service (for example both FTP and web service), it might be better to
specify a range of port numbers. You can allocate a server IP address that corresponds to a port or
a range of ports.
The most often used port numbers and services are shown in
. Please refer
to RFC 1700 for further information about port numbers.
Note: Many residential broadband ISP accounts do not allow you to run any server
processes (such as a Web or FTP server) from your location. Your ISP may
periodically check for servers and may suspend your account if it discovers any
active services at your location. If you are unsure, refer to your ISP.
Configuring Servers Behind Port Forwarding (Example)
Let's say you want to assign ports 21-25 to one FTP, Telnet and SMTP server (
A
in the example),
port 80 to another (
B
in the example) and assign a default server IP address of 192.168.1.35 to a
third (
C
in the example). You assign the LAN IP addresses and the ISP assigns the WAN IP address.
The NAT network appears as a single host on the Internet.
Summary of Contents for VMG5313-B10A
Page 15: ...15 PART I User s Guide ...
Page 16: ...16 ...
Page 32: ...Chapter 2 The Web Configurator VMG5313 B10A B30A Series User s Guide 32 ...
Page 40: ...Chapter 4 Tutorials VMG5313 B10A B30A Series User s Guide 40 ...
Page 71: ...71 PART II Technical Reference ...
Page 72: ...72 ...
Page 78: ...Chapter 5 Network Map and Status Screens VMG5313 B10A B30A Series User s Guide 78 ...
Page 106: ...Chapter 6 Broadband VMG5313 B10A B30A Series User s Guide 106 ...
Page 162: ...Chapter 9 Routing VMG5313 B10A B30A Series User s Guide 162 ...
Page 180: ...Chapter 10 Quality of Service QoS VMG5313 B10A B30A Series User s Guide 180 ...
Page 198: ...Chapter 11 Network Address Translation NAT VMG5313 B10A B30A Series User s Guide 198 ...
Page 210: ...Chapter 14 Interface Group VMG5313 B10A B30A Series User s Guide 210 ...
Page 218: ...Chapter 15 USB Service VMG5313 B10A B30A Series User s Guide 218 ...
Page 232: ...Chapter 17 Firewall VMG5313 B10A B30A Series User s Guide 232 ...
Page 240: ...Chapter 19 Parental Control VMG5313 B10A B30A Series User s Guide 240 ...
Page 250: ...Chapter 21 Certificates VMG5313 B10A B30A Series User s Guide 250 ...
Page 296: ...Chapter 23 Voice VMG5313 B10A B30A Series User s Guide 296 ...
Page 300: ...Chapter 24 Log VMG5313 B10A B30A Series User s Guide 300 ...
Page 308: ...Chapter 27 xDSL Statistics VMG5313 B10A B30A Series User s Guide 308 ...
Page 318: ...Chapter 30 Remote Management VMG5313 B10A B30A Series User s Guide 318 ...
Page 322: ...Chapter 32 TR 064 VMG5313 B10A B30A Series User s Guide 322 ...
Page 332: ...Chapter 36 Log Setting VMG5313 B10A B30A Series User s Guide 332 ...
Page 336: ...Chapter 37 Firmware Upgrade VMG5313 B10A B30A Series User s Guide 336 ...
Page 352: ...Chapter 40 Troubleshooting VMG5313 B10A B30A Series User s Guide 352 ...
Page 354: ...354 ...
Page 374: ...Appendix B Wireless LANs VMG5313 B10A B30A Series User s Guide 374 ...
Page 390: ...Appendix E Legal Information VMG5313 B10A B30A Series User s Guide 390 ...