Backup paths to the internet.

[Joep L. Blom]

Kipton Moravec wrote:
> I am planning to use a computer as a gateway/firewall running Ubuntu (or
> another version of Linux).
> 
> What is the utility, or service, I need to allow different paths to the
> Internet through this gateway?
> 
> For example, the primary path to the Internet is through eth0 the first
> Ethernet card in the computer.  However if that gateway is down, then I
> want it to use a second path (or a third if #2 is down also). I can make
> it another card (eth1), or another IP address on the first card. Finally
> if all else fails, I would want it to dial up (or use a serial port) to
> establish a slow but functioning connection.
> 
> When the first path is active again it goes back to the original
> configuration. 
> 
> I want this to happen at the gateway computer, so the users do not see
> anything, except for a reduction in performance if I go to a slower
> connection.
> 
> What is this called, and what do I have to read up on? 
> It is more than just IP Tables right?
> 
> Kip
I would advise to use the LEAF firewall
http://leaf.sourceforge.net/

This a standalone distribution and very small. It fits (if you want it 
lean) even on a floppy disk but there are distributions for using it 
from an CD, USB-stick, etc.
The firewall software is shorewall and it is a real hardware firewall 
using 2 ethernet cards and not the pseudo-firewalls as offered for 
Windows. I use it for > 8 years and the only time I realise it's there 
when we have had a power outage.
Success
Joep