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 From:  "Sancho2k.net Lists" <lists at sancho2k dot net>
 To:  "M.K." <kraus at seznam dot cz>
 Cc:  Monovall Lists <m0n0wall at lists dot m0n0 dot ch>
 Subject:  Re: [m0n0wall] How works Outbound NAT?
 Date:  Tue, 09 Dec 2003 17:16:03 -0700
M.K. wrote:

> Hi,
> I know inbound, 1:1 NATs. Can You clear me, how works outbound NAT? I ment
> that contrariwise as inbound (more public IP to one internal - f.e.server),
> but the setting is different...

I'll take a stab at it. 1:1 nat maps one outside address to one inside 
address. One address is translated to another. 1:many is in effect PAT 
(port address translation) where an entire subnet (say 10.0.1.x) on the 
inside interface can be translated to a single public address (say 
1.2.3.4). Relationships to determine where replies are sent back to 
which client inside are mapped by port number. So say 10.0.1.3 makes an 
outbound HTTP request to a public server, he hits the router/firewall 
where his connection out is assigned to TCP port 35555. When a reply 
comes back from the remote web server to port 35555, the router/firewall 
will accept that response and forward it to 10.0.1.3. Sort of a virtual 
mapping by port.

HTH

DS