Chapter 5 WAN Setup
P-2812HNU-51c User’s Guide
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Packets have not been sent from 1, A to 4, E or 5, so they cannot send packets to
1, A.
Figure 54 Port Restricted Cone NAT Example
Symmetric NAT
The full, restricted and port restricted cone NAT types use the same mapping for
an outgoing packet’s source address regardless of the destination IP address and
port. In symmetric NAT, the mapping of an outgoing packet’s source address to a
source address in another network is different for each different destination IP
address and port.
In the following example, the P-2812HNU-51c maps the source address IP
address 1 and port A to IP address 2 and port B on the external network for
packets sent to IP address 3 and port C. The P-2812HNU-51c uses a different
mapping (IP address 2 and port M) for packets sent to IP address 4 and port
D.
A host on the external network (IP address 3 and port C for example) can only
send packets to the internal host via the external IP address and port that the NAT
router used in sending a packet to the external host’s IP address and port. So in
1, A
2, B
4, D
4, E
3, C
5
