Ubuntu Server with 2 NICs, help with routing

[Karl Auer]

On Sun, 2014-03-23 at 13:05 +1300, Roland Hill wrote:
> > Can you get to the Internet from the server?
> 
> Yes. I can ping "external" IP's and get an appropriate response.

If you can get out from the server, but not from a host on the inside
interface of the server, there are really only three possibilities:

- the host is not actually connected to the same network as the inside
interface of the server :-)

- there is a routing problem

- there is a packet filtering problem.

The second is by far the likeliest. At this point I would suggest that
you check the default router on the host. It needs to have a default
route pointing at the server. The default router can be statically
configured on each host, distributed as an option via DHCP, or
distributed via a routing protocol. For dnsmasq, add something like this
to your command line:

   --dhcp-option=option:router,192.168.0.1

Putting it all together:

- the host needs a default route to get to the server:

    0.0.0.0 -> 192.168.0.1

- the server needs a default route to get to the router

    0.0.0.0 -> 10.0.0.1

- the router needs a default route to get to the Internet

   0.0.0.0 -> ISP

If that doesn't work, report back :-)

Regards, K.



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Karl Auer (kauer at biplane.com.au)
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