Networking : how to bridge two NICs to share internet access ?

[Vincent Trouilliez]

> Vincent,
> 
> You probably already realize that what you're endeavoring to do with
> your "multi-homed" Linux box is in essence what a "broadband NAT
> (network address translation) router" does for the typical home/small
> office environment.  Such routers typically include wireless
> capability these days, e.g., Netgear WGT624 and others by Linksys,
> D-Link, etc.  The "broadband" term refers to the port for the DSL or
> cable modem, i.e., the internet access.  Because of the NAT, such a
> router is in many respects a natural firewall, and most commercial
> devices include additional firewall functions.
> 
> To focus on a particular element of your setup, the Ethernet port
> fixed to ip address 10.0.0.0, which port would correspond to one of
> several (typically four) on the commercial routers for home use, I
> would like to call your attention to one of the documents that govern
> the internet architecture:  RFC 1918 - Address Allocation for Private
> Internets (link below):
> 
> http://www.faqs.org/rfcs/rfc1918.html
> 
> This document (one of a large family of internet governing documents)
> addresses the question of what address to use on the "private" side of
> the router, and therefore addresses your comment, "...since I don't
> know any better..."
> 
> Reinventing the wheel is a great way to learn; but at some point, it's
> useful to know what those who have gone before have done.
> 
> Also, for your Linux box to be useful as a router and firewall to
> provide internet access to other networked systems you will probably
> need at least a couple more Ethernet ports.
> 
> Recommended reading (besides the RFC documents):  TCP/IP Illustrated
> Volume 1 by W. R. Stevens.
> 
> Good luck!
> 
> Bill Chapman


Hi Bill, 

Wow, I am not sure I understand everything you said, I am getting lost
already :-/  Do you mean, in essence, that :

1) networking is a very vast and immensely complex subject ?
2) I should give up trying to feed internet access to eth1 from eth0 ?
3) there are cheap/consumer devices named 'routers' that can take care
of all the problems in hardware, and let me enjoy all the benefits with
next to zero, or only moderate, pain ?

Looks like I will need one of these little things then... how much do
they cost ? Maybe I can get a dirty cheap one on ebay ?
4 ports would be enough : one for my main desktop machine, one for
another machine (project in the pipeline...) that will back-up daily the
data from the main machine, a third port to connect a laptop eventually,
and a free port for future extensions or I don't know...


Regards,


--
Vince