[kwlug-disc] IP addresses and gateways--my google-fu seems to be lacking

unsolicited unsolicited at swiz.ca
Thu Jan 16 17:54:31 EST 2014


Brent, your message isn't quite as clear as you might like.

Start with the netbook.

When you connect the wire as you say, does the netbook stay happy in 
terms of internet? If not, that's the problem to solve first. (Worry 
about the other computers afterwards.)

Output of 'route' will be helpful for that. The default route, for it, 
should be 192.168.1.1 (I'm guessing .1 is the router downstairs.)

 From your description, it sounds like you're getting two default routes 
upon the second connection. If that's so, the second 'default' route may 
appear as '0.0.0.0'.

The answer to your question, but I'm going to suggest you change your 
solution slightly, the computers that connect to the netbook's default 
route is the ip address of the netbook on the .10. range.

The solution is probably to specify no gateway on the wired connection 
of the gateway (netbook). (Leaving you with only one gateway, the 
downstairs router.)

I have not shared a linux connection, to give you more specifics, but 
I'll suggest you change the netbook networking to use bridged mode. I'm 
guessing you're probably doing some sort of internet connection sharing 
/ NAT at the moment.

If you bridge the interfaces, then you can leave all the networking of 
everything else as it always has been. i.e. 192.168.1.x

Think of Cambridge, one city separated by a river. Bridges link the two 
sides. Same thing with networking.

The computers connecting to the netbook will request DHCP as always, the 
request goes to the netbook, the netbook passes it on to the router, it 
sends back to the originating computer via the netbook.

Everything stays on .1. and the world stays happy as you're used to, and 
you avoid the complexity that's not buying you anything at the moment of 
the .10. network.

Others who have done this will have to comment on the specifics. 
Although I understand the networking, I don't have the specific linux 
command lines to hand in my head.

In the mean time, hopefully your initial question got answered above.


On 14-01-16 01:18 PM, R. Brent Clements wrote:
> I was using an Ethernet-over-power device until a couple days ago when
> one end of it burned out.  I am trying to configure my old netbook to
> connect wirelessly to the downstairs router (easy) and share the
> internet connection with the network of computers in my bedroom.
> Whenever I attach the network cable to the system I lose the internet.
>   I can ping the ip address of both sides of the "router" computer, but
> nothing beyond that.  I am using static ip addresses for the inner
> network in the 192.168.10 range, and the wireless address is
> 192.168.1.65 assigned dynamically from the wireless router downstairs.
>
> I am wondering what gateway address I need to assign to the lan-side
> eth0.  I have followed the instructions on several sites about
> configuring iptables.  It seems like the netbook is losing the
> internet when I have two interfaces active, even tho only one has an
> internet connection.
>
> Brent
>
>
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