Full Cone Nat; Restricted Cone Nat; Figure 30 Full Cone Nat: Outgoing; Figure 31 Full Cone Nat: Incoming - ZyXEL Communications Prestige 2302R User Manual

Prestige 2302R Series User's Guide

6.3.2.1 Full Cone NAT

In full cone NAT, the NAT router maps the source address of all outgoing packets to one IP
address and port on another network. The NAT router also maps packets coming to that
address and port on the other network back to the original source address.
6.3.2.1.1 Full Cone NAT: Outgoing
See the following figure. The Prestige (X) uses port 80 to send some packets to server Y. The
Prestige's IP address is 10.0.0.3 (a private IP address). The NAT router receives the packets
from the Prestige with the private source address 10.0.0.3:80 and changes them to use public
source address a.b.c.d:30080 before forwarding them on to Y.

Figure 30 Full Cone NAT: Outgoing

6.3.2.1.2 Full Cone NAT: Incoming
Servers Y and Z can both send packets to IP address a.b.c.d and port 30080. The NAT router
changes the destination address to the private IP address 10.0.0.3 and port 80 and sends it to
the Prestige.

Figure 31 Full Cone NAT: Incoming

6.3.2.2 Restricted Cone NAT

For all outgoing packets, restricted cone NAT maps the source address to one IP address and
port on another network. This is the same as full cone NAT (see
for an example).
However, packets can only be sent back through NAT from an IP address to which packets
have been sent from the original source address.
In the following example, X already sent a packet to Y, so Y can send a packet to X. X did not
send a packet to Z, so Z cannot send packets to X.
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Section 6.3.2.1.1 on page 86
Chapter 6 Introduction to VoIP