[NCLUG] DSL modem + Wireless Router setup

[Chad Perrin]

On Thu, Sep 07, 2006 at 05:43:43AM -0600, Sean Reifschneider wrote:
> On Wed, Sep 06, 2006 at 01:19:46PM -0600, Chad Perrin wrote:
> >That shouldn't necessarily be a problem, though I've not used that
> >router, so I don't know.  You should be able to change your internal
> >network to 192.168.2.x instead, though.
> 
> Most systems are quite unhappy to have the same network on multiple
> interfaces.  At the very least, the kernel is going to see the two routes
> for the same network, and may not select the right one for trying to push
> traffic over.  I've seen it cause all sorts of weirdness, particularly if,
> say, your default gateway on the DSL is 192.168.1.1, and the Linksys also
> has 192.168.1.1 and therefore sees it as a local destination.

It certainly takes a more-complex setup to make things play nicely
together if your network segments duplicate some IP addresses.  To
protect against that eventuality, it is definitely a good idea to assign
your local network a different IP range than the outside network.  Using
the same IP range doesn't gaurantee that there will be a conflict,
though, as long as no IP addresses are duplicated.

On the other hand, ISPs tend to get grumpy when you futz with their
routing schemes, so it's definitely in one's best interest to just
segregate the local network from the ISP as much as possible.


> 
> If you're asking on a mailing list, then having the same network on
> multiple interfaces should probably be considered a bug.  The times I've
> legitimately done that in the last decade are less than 10...

I agree -- avoid it when you can.  Even when it can "legitimately" be
done, there's usually a better option.

-- 
CCD CopyWrite Chad Perrin [ http://ccd.apotheon.org ]
Brian K. Reid: "In computer science, we stand on each other's feet."