How does NAT identify a specific host behind a firewall?

[lpress]

When doing NAT, where is the identifier of the specific host inside the firewall stored?

Is it in the high order bits of the Port field in the TCP segment?

[l.mourits]

Hi,

The PIX keeps track on all translations via the xlate table. For every flow a translation entry is created.

Kind Regards,

Leo

[tvanginneken]

Hi,

if you use static NAT, there is a one-to-one connection between the public and the private IP address.

If you use PAT, the pix modifies the sender's source port (upd of tcp) when the packet goes through the pix. Each internal host gets it's own source port when it makes a connection through the pix to a host on the outside.

Kind Regards,

Tom