[CLUE-Tech] linux & broadband

[David Anselmi]

A quick answer to part of your questions.  Masquerading (now called NAT
- network address translation) is when your gateway machine converts the
IP addresses on connections from an internal machine.  The internal
machines use private addresses, so when one sends traffic out to the
Internet, the source address must be translated into the IP address of
the gateway.  That way the answer will come back to the right place.
The gateway keeps track of what connections go where so that incoming
packets get the destination IP changed to the correct internal address.
This is also called SNAT (S for source, the originator of the
connection).

Port mapping (aka port forwarding) is a type of DNAT (D for destination,
the receiver of the connection).  When the gateway gets a connection
request from the Internet the destination IP is translated based on the
port requested so that the connection goes to the correct internal
machine.  This is necessary if you run a web server (e.g.) behind the
gateway.  When someone wants to connect to the web server, all they know
is the gateway's (public) IP, and port 80.  Since the connection starts
outside your network, the gateway doesn't know what internal machine
should handle it, unless you tell it in the port forwarding
configuration.

For more, see
http://netfilter.samba.org/unreliable-guides/NAT-HOWTO/index.html.

Hope that helps.

Dave

Himanshu Sharma wrote:

> >8 snip
> Are portmapping and masquerading different? If they are, which way do
> I want to go?
> >8 snip