P-2002 Series User’s Guide

NAT may be implemented on a device that is between your Prestige and the Internet.

5.3.1 NAT Example

See the following figure. The Prestige (X) sends packets to the Internet. The Prestige’s IP address is 10.0.0.3. This is a private or internal IP address. The NAT router maps the private source IP address to a public source IP address (a.b.c.d). The public source IP address is also known as the external IP address.

Note: The NAT figures in this chapter use lower-case letters (like a.b.c.d for example) to represent public IP addresses.

Figure 17 NAT: Outgoing

When the NAT router receives packets with destination address IP address a.b.c.d, the NAT router changes a.b.c.d back to the private IP address 10.0.0.3 and sends it to the Prestige.

Figure 18 NAT: Incoming

5.3.2 NAT Types

This section discusses the following NAT types that may be implemented on a router in front of the Prestige.

•Full Cone

•Restricted Cone

•Port Restricted Cone

•Symmetric

Chapter 5 Introduction to VoIP

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