Chapter 5 WAN Setup

send them to the server 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 53 Restricted Cone NAT Example

3

4, D

1, A

2, B

 

 

4, E

 

5

Port Restricted Cone NAT

Port restricted cone NAT 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 P-2812HNU-51c 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. A host on the external network (IP address 3 and Port C 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 and port.

A server with IP address 1 and port A sends packets to IP address 3, port C and IP address 4, port D. The P-2812HNU-51c changes the server’s IP address to 2 and port to B.

Since 1, A has already sent packets to 3, C and 4, D, they can send packets back to 2, B and the P-2812HNU-51c will perform NAT on them and send them to the server at IP address 1, port A.

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P-2812HNU-51c User’s Guide