probe router wirelessly, double NAT

[Colin Law]

On 29 December 2013 09:51, thufir <hawat.thufir at gmail.com> wrote:
> On Sun, 29 Dec 2013 08:45:31 +0100, Nils Kassube wrote:
>
>> thufir wrote:
>>> I'm having some trouble with vuze, so am looking at some networking.
>>> The computer uses a wifi adapter to connect with the router.  The
>>> adapter is a bit unusual:
>>>
>>> http://www.iogear.com/product/GWU627/
>>>
>>> So the computer gets an IP address from the adapter, and the adapter
>>> gets an IP address from the router.  Presumably this is double-NAT?
>>
>> I had a look at the manual of your GWU627 and I think the device works
>> as a bridge and you have single NAT from your router.
>>
>>> thufir at dur:~$ ifconfig eth0      Link encap:Ethernet  HWaddr
>>> 00:13:20:ac:13:b0
>>>           inet addr:192.168.0.15  Bcast:192.168.0.255
>>
>> [...]
>>
>>> thufir at dur:~$ traceroute 192.168.1.1
>>
>> 192.168.1.1 is a private IP address which is only used in your local
>> network. Do you have a machine with that IP in your LAN? Or is it a typo
>> and you meant 192.168.0.1 which seems to be your router?
>>
>>> traceroute to 192.168.1.1 (192.168.1.1), 30 hops max, 60 byte packets
>>>  1  192.168.0.1 (192.168.0.1)  1.364 ms  6.244 ms  6.238 ms 2  * * *
>>>  3  64.59.147.161 (64.59.147.161)  19.651 ms  21.628 ms  21.655 ms 4
>>>  rc2bb-tge0-4-0-5.vc.shawcable.net (66.163.69.33)  21.772 ms rc2bb-
>>> tge0-13-0-10.vc.shawcable.net (66.163.69.141)  24.005 ms rc2bb-
>>> tge0-13-0-6.vc.shawcable.net (66.163.69.137)  23.947 ms
>>
>> Your router tries to find the way to 192.168.1.1 via the public
>> internet. That can't work because private addresses should not be
>> reachable that way.
>>
>>
>> Nils
>
>
> Exactly, the GWU627 is a bridge.  My ip address is in 192.168.0.x, that's
> what the bride provides.
>
> http://192.168.0.1/Docsis_system.asp in firefox brings up the interface
> for the Cisco DPC3825 DOCSIS 3.0 Gateway (router).
>
> I **believe** that the DPC3825 gives out addresses in the 192.168.1.x
> range, but I see it as 192.168.0.1 because the GWU627 is a bridge.
>
> Is the above a correct understanding?

No, a bridge is effectively a transparent device on the network
joining the two parts together.  The Cisco gateway is (from what you
describe) giving out addresses in the 192.168.0.x range and they get
passed straight through the bridge without modification.  To probe the
router just use 192.168.0.1 whichever side of he bridge you are.

Colin