[CoLoCo] changing subnet mask

Jim Hutchinson jim at ubuntu-rocks.org
Tue Sep 9 23:00:40 BST 2008

On Tue, Sep 9, 2008 at 3:43 PM, Kevin Fries <kfries at cctus.com> wrote:

> ________________________________________
> From: ubuntu-us-co-bounces at lists.ubuntu.com [
> ubuntu-us-co-bounces at lists.ubuntu.com] On Behalf Of Jim Hutchinson [
> jim at ubuntu-rocks.org]
> Sent: Sunday, September 07, 2008 8:23 PM
> To: mitch at kci.net; Ubuntu Colorado Local Community Team
> Subject: Re: [CoLoCo] changing subnet mask
> On Sun, Sep 7, 2008 at 6:54 PM, Mitch Mahan <mitch at kci.net<mailto:
> mitch at kci.net>> wrote:
> Don't use DHCP on the second router.
> Connect the second router to the first router via the second routers "LAN"
> port.
> Make the second router's ip<>
> I actually tried that first but for whatever reason it wouldn't get an ip
> address. Maybe it's still part of the issue with dd-wrt. Assuming I can get
> it to work, will computers that connect to the second router still get an ip
> assigned via dhcp from the first router?
> ________________________________________
> Jim,
> I am not sure what you are trying to do, but your setup seems odd to say
> the least.  Forget what you are doing, tell me exactly what you are trying
> to accomplish.
> Kevin
> --

I don't think it's that odd. It's probably just not that clear what I'm
doing. I have two routers - router 1 is a linksys running dd-wrt and router
2 is a dlink. Router 1 connects to my modem and until I added router 2 it
was the only one on the network. However, for some reason, computers running
Linux and with a broadcom wifi are having trouble connecting to the linksys.
As this was creating issues with networking for the family I stuck the dlink
into the mix so they could connect while I worked on figuring out why the
linksys was having issues. However, once connected it was not possible to
admin the dlink router as it was on a different subnet. I had a set up like
this in the past with different subnets so that my home network was shielded
from an ssh box I was running on the other subnet. However, in that case the
home network was downstream (i.e. the second router) and was able to see
upstream connections (computers on 192.168.2.x could see 192.168.1.x or
maybe it was because router 2 was plugged into router 1 and router 1 plugged
into the modem). In the new scenario, the dlink is the downsteam one (i.e.
plugged into router 1 and my desktop also connects to router 1) and couldn't
be seen. I really didn't want to move everything around but I figured that
if I changed the subnet mask then everything would be able to see
everything. My thinking was that computers on differnt subnets can't see
each other if the mask is "masking".

Now, if that doesn't make sense it's probably because I have just enough
networking knowlege to cause problems and don't always understand why things
work the way they do. Doing as Mitch suggested (lan to lan) with everything
on 192.168.1.x and no dhcp on the dlink solved the issue - albiet not in the
way I was trying to. I was hoping to gain a bit more understanding of
subnets for now the problem is solved.

If you know of any good and simple resources that would help me to
understand this stuff that would be great. Most things I find don't really
simplify. I need a children's guide to networking with nice pictures :)


Jim (Ubuntu geek extraordinaire)
Please avoid sending me Word or PowerPoint attachments.
See http://www.gnu.org/philosophy/no-word-attachments.html
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