Zyxel-communications P-2002 Manual de usuario descargar pdf (Pagina 51)

P-2002 Series User’s Guide

Chapter 5 Introduction to VoIP 51

Figure 19 Full Cone NAT Example

5.3.2.2 Restricted Cone NAT

As in full cone NAT, a restricted cone NAT router maps all outgoing packets from an internal

IP address and port to a single IP address and port on the external network. In the following

example, the NAT router maps the source address of all packets sent from internal IP address

1 and port A to IP address 2 and port B on the external network.

The difference from full cone NAT is in how the restricted cone NAT router handles packets

coming in from the external network. A host on the external network (IP address 3 or IP

address 4 for example) can only send packets to the internal host if the internal host has

already sent a packet to the external host’s IP address.

A Prestige with IP address 1 and port A sends packets to IP address 3 and IP address 4. The

NAT router changes the Prestige’s IP address to 2 and port to B.

Both 4, D and 4, E can send packets to 2, B since 1, A has already sent packets to 4. The NAT

router will perform NAT on the packets from 4, D and 4, E and send them to the Prestige at IP

address 1, port A. Packets have not been sent from 1, A to 3 or 5, so 3 and 5 cannot send

packets to 1, A.

Figure 20 Restricted Cone NAT Example

1 2 ... 46 47 48 49 50 51 52 53 54 55 56 ... 167 168

Sin comentarios

Zyxel-communications P-2002 Manual de usuario Pagina 51