Re: how does outgoing nat work exactly?

[Jeffery . Gieser]

Rick,

        There are a couple of ways this can be done and it depends on how the NAT device works.  NAT, itself, is just the rewriting of the source IP address.  If your NAT device is an application layer gateway then you would have two seperate connections.  One would be between your internal device and the ALG and the other between the ALG and the server you are connecting to.  This would more than likely result in a different source port for each connection since all of the headers would be re-written by the ALG.  If you have some sort of IP filter, router, or loadbalancer doing NAT then the only thing that will change in the packet will be the source address.  The rest of the headers will remain intact including the source port.  The same would probably be true of a Stateful Inspection style firewall depending on how it was built.

Regards,
Jeffery Gieser