Configure NAT traversal with two Linux machines

Use two Linux machines to configure NAT traversal-Linux Enterprise Application-Linux server application information. See the following for details. 1. Use two Linux machines to configure NAT through iptables

2. Use stund (vovida.org) to test the NAT type port restricted nat type. You can only configure the symmetric nat type for iptables.

3. Use the sip client to test the traversal.

4. The NAT ing port is actually the same as that allocated by the Intranet. Still cannot be crossed, because the port mapped by one nat is always 1024 or 1025

5. Chen Hui wrote the udpclient test. The result is: when there is external data access to the unused port port1 of nat, the port mapped to the data of the same number of port1 after nat is 1024 or 1025.

6. Conclusion: when both parties are port restricted nat type or specified Ric nat type, it cannot be crossed.

7. Test QQ and find that it uses server forwarding for audio and video data communication.