Chapter 5 WAN Setup
P-2812HNU-51c User’s Guide
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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
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.
1, A
2, B
4, D
4, E
3
5
