ZyXEL P-2812HNU-F1 User Guide - Page 189

Network Address Translation NAT

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CHAPTER 10 Network Address Translation (NAT) 10.1 Overview NAT (Network Address Translation - NAT, RFC 1631) is the translation of the IP address of a host in a packet, for example, the source address of an outgoing packet, used within one network to a different IP address known within another network. 10.1.1 What You Can Do in this Chapter • Use the Port Forwarding screen to configure forward incoming service requests to the server(s) on your local network (Section 10.2 on page 190). • Use the Sessions screen to limit the number of concurrent NAT sessions each client can use (Section on page 192). 10.1.2 What You Need To Know The following terms and concepts may help as you read this chapter. Inside/Outside and Global/Local Inside/outside denotes where a host is located relative to the Device, for example, the computers of your subscribers are the inside hosts, while the web servers on the Internet are the outside hosts. Global/local denotes the IP address of a host in a packet as the packet traverses a router, for example, the local address refers to the IP address of a host when the packet is in the local network, while the global address refers to the IP address of the host when the same packet is traveling in the WAN side. 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. P-2812HNU(L)-Fx Series User's Guide 189

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P-2812HNU(L)-Fx Series User’s Guide
189
C
HAPTER
10
Network Address Translation (NAT)
10.1
Overview
NAT (Network Address Translation - NAT, RFC 1631) is the translation of the IP address of a host in
a packet, for example, the source address of an outgoing packet, used within one network to a
different IP address known within another network.
10.1.1
What You Can Do in this Chapter
Use the
Port Forwarding
screen to configure forward incoming service requests to the server(s)
on your local network (
Section 10.2 on page 190
).
Use the
Sessions
screen to limit the number of concurrent NAT sessions each client can use
(
Section
on page 192
).
10.1.2
What You Need To Know
The following terms and concepts may help as you read this chapter.
Inside/Outside and Global/Local
Inside/outside denotes where a host is located relative to the Device, for example, the computers
of your subscribers are the inside hosts, while the web servers on the Internet are the outside
hosts.
Global/local denotes the IP address of a host in a packet as the packet traverses a router, for
example, the local address refers to the IP address of a host when the packet is in the local
network, while the global address refers to the IP address of the host when the same packet is
traveling in the WAN side.
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.