[plug] IP Masquerading

[Greg Mildenhall]

On Wed, 2 Dec 1998, John Breen wrote:
> I have:
> 1.  Rebuilt my kernel with the right options
A 2.0.x kernel, I presume?

> 2.  Made the right modules
> 3.  Installed modules in rc.local
> 4.  Assigned valid local IPs to all machines on my network 
> (linux=192.168.1.1, wombat=192.168.1.5, wallaby=192.168.1.3, 
> netmask=255.255.255.0)
> 5.  Set up a ppp connection to my ISP with pppd.  This bit 
> definitely works, as I can dial up and browse the web.
> 6.  Set up the nameserver for non-local addresses to my ISPs DNS.
> 7.  Configured my windows 95/98 machines to use the linux box as 
> the gateway
Have you set them up to use the correct DNS, too?

> 8.  Set up IP Forwarding policies on the linux box with ipfwadm
> 
> According to the HOWTO, that's about all I need to do.  I should 
> now be able to see the internet from my other boxes without any 
> problems at all. Problem is, it don't go!
> The web side of things I got around by setting up squid.  That 
> works well.
OK, then the connections must all be right, which confines the problem to
routing. Firstly, make sure the clients have the server as their gateway
(in the TCP/IP settings)
Secondly, ensure that IP forwarding is enabled:
# cat /proc/sys/net/ipv4/ip_forward
Should give a result of 1.
Thirdly, give us a look at your firewall rules - i.e.:
# ipfwadm -F -l -n
So we can be sure they're correct.

That ought to be enough detail to sort out the problem.

-Greg Mildenhall