Chapter 5 WAN Setup
P-870HN-51D User’s Guide
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packets sent to IP address 2 and port B and forwards them to IP address 1, port
A.
Figure 39 Full 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-870HN-51D 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-870HN-51D 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
2, B
1, A
