[lug] Networking problem DSL modem

Nate Duehr nate at natetech.com
Thu Sep 11 22:12:00 MDT 2008


On Sep 11, 2008, at 12:58 PM, gordon.golding at colorado.edu wrote:

>
> So - many good thoughts:
>
> Sorry - IP is 192.168.1.1 for DSL router ( or is it .0.1 ??  - hmmm,  
> no brain cells).  I'm pretty sure that it just has the one address  
> ( ie - 4 addresses, network, gateway, my PC, broadcast).  They had  
> to replace it at one point, so I don't remember the make/model, will  
> get that at home.

Okay, that'll be helpful.

> 1) >>>> Even if one machine is turned off, it may still be  
> responding.  I think both machines have ""network power on" - so the  
> ethernet cards must stay live and are probably fighting over the one  
> available address.

This shouldn't be a problem, most "Wake-on-LAN" features are done via  
Layer 2 (MAC) protocols, not Layer 3 (IP), and if the operating system  
on the machine is off, the machines won't respond to Layer 3  
networking requests.  Thus, no IP conflict.

> 2)>>>Some ISPs will restrict your modem to only server addresses to  
> one MAC
> address.  It might react badly to you switching PCs unless you are
> also MAC spoofing.

I'm thinking this is the problem also, but... will help to know what  
modem.  Knowing it's Qwest, I haven't been on DSL in a while to know  
what they've been up to as far as the "rules" on their recent crop of  
really cruddy little DSL devices.  (Sure makes one pine for the days  
when they provided a Cisco 678 with every DSL connection, doesn't it?)

> 3)  >>>SOHO networking can be a real mess.  To add a bit to the  
> confusion, I
> suspect he already has a NAT router, since he claims to be getting .1
> and .2 addresses, which (I'm guessing here) are 192.168.x or 10.x.  If
> this is the case, he should be able to simply widen the mask and maybe
> the DHCP pool on the existing router, assuming his ISP didn't cripple
> it or lock him out.
>
> This is a Great thought - they have to buy "on the market" stuff.   
> Maybe I can reconfigure what they sent to have a bigger pool.

That's definitely what you want to find out if you can do... any DSL  
"modem"/router worth its salt should be able to provide a full Class-C  
sized (sorry, old-school... make that a /24 network in today's network  
terminology since classful routing was gone long-long ago) DHCP pool  
and NAT 253 devices behind it.

Usually (if they haven't locked you out) you can see things like this  
by pointing a web browser at the router IP address (from the machine  
that works, of course) and see what the settings are, etc.  You'll  
probably need some kind of username and password that they've  
(hopefully) provided you.

--
Nate Duehr
nate at natetech.com






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