RFC3489:
Full Cone: A full cone NAT is one where all requests from the same internal IP address and port are mapped to the same external IP address and port Furthermore, any external host can send a packet to the internal host, by sending a packet to. The Mapped External Address.
Restricted Cone: A restricted cone NAT is one where all requests from the same internal IP address and port are mapped to the same external IP address and port Unlike a full cone NAT, an external host (with IP address X) can send a packet. To The Internal Host Only The Internal Host Had Previously Sent A Packet To IP Address X.
Port Restricted Cone: A port restricted cone NAT is like a restricted cone NAT, but the restriction includes port numbers Specifically, an external host can send a packet, with source IP address X and source port P, to the internal host only if the. INTERNAL HOST HAD PREVIOSLY SENT A Packet To IP Address X and Port P.
Symmetric: A symmetric NAT is one where all requests from the same internal IP address and port, to a specific destination IP address and port, are mapped to the same external IP address and port If the same host sends a packet with the same source. Address and Port, But to a Different Destination, A Different Mapping IS Used. Furthermore, Only The External Host That Receives A Packet CAN Send A UDP Packet Back to The Internal Host.
Fully tapered: All from the same internal address, port request, is mapped to the same external address, port. Also, any external host can send the packet to the internal host by sending a data packet to the external address, port of the map. The requester learned the external network mapping of the intranet host through the public network server, and the data package can be sent to the main network.
Restricted tapered: All from the same internal address, port request, is mapped to the same external address, port. Unlike the full cone NAT, the external host (IP address is x) can only send the packet to the internal host only if the internal host transmits an over-numerical packet to the external IP address x. The request party sends a request through the public server, allowing the internal network host to send a packet to the requester to send the data package to the internal network host. The port is limited: similar to the restricted cone, but increasing the limit of ports. Clearly, the external host only sends a packet to the internal host with the IP address x, the port P is transmitted to the external IP address x, and the port P is transmitted. Requests use a resolved cone solution.
Parallel: All from the same internal address, port, requests to the same external address, port, are mapped to the same address, port. If the same host uses the same IP address, the port is sent to a different external IP address, the port will use different mappings. Also, only the external host of the data packet issued over the intranet can send the packet back to the intranet host. Requests use a resolved cone solution. However, if the requester is in the same NAT and the requested party, the packet will not be sent to each other.
