Network Address Translation (Nat); Overview; What You Can Do In This Chapter; What You Need To Know - ZyXEL Communications P870HNU-51B User Manual

Network Address Translation (NAT)

8.1 Overview

This chapter discusses how to configure NAT on the Device.
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.

8.1.1 What You Can Do in this Chapter

• The Port Forwarding screen lets you configure forward incoming service requests to the
server(s) on your local network
• The DMZ Host screen lets you configure a default server
• The ALG screen lets you enable SIP ALG on the Device

8.2 What You Need to Know

The following terms and concepts may help as you read through this chapter.
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.

8.3 The Port Forwarding Screen

This summary screen provides a summary of all port forwarding rules and their configuration. In
addition, this screen allows you to create new port forwarding rules and delete existing rules.
P-870HNU-51b User's Guide
(Section 8.3 on page 151).
(Section 8.5 on page
(Section 8.4 on page 155).
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