2 wire DSL

Luke Militello luke at digitalenigma.net
Sun Dec 7 05:38:21 UTC 2008


Leonard Chatagnier wrote:
> --- On Sat, 12/6/08, Luke Militello <luke at digitalenigma.net> wrote:
> 
>> From: Luke Militello <luke at digitalenigma.net>
>> Subject: Re: 2 wire DSL
>> To: "Ubuntu user technical support, not for general discussions" <ubuntu-users at lists.ubuntu.com>
>> Date: Saturday, December 6, 2008, 11:18 PM
>> Leonard Chatagnier wrote:
>>> --- On Sat, 12/6/08, Luke Militello
>> <luke at digitalenigma.net> wrote:
>>> BIG SNIP
>>>> Sounds to me the problem is a double NAT.  From
>> what I am
>>>> reading... is 
>>>> this how your network is setup?
>>>>
>>>> INET <----> 2WIRE-DSL <----> WIFI-RTR
>>>> <----> END-USERS
>>>>
>>>> Most DSL routers do NAT by default, however lack
>> the option
>>>> of WiFi 
>>>> capabilities so most users opt for a secondary
>> router.  If
>>>> your network 
>>>> is like the one above, then your WiFi router is
>>>> "NAT'ing" down to one IP 
>>>> address on the "DSL network".  Although
>> double
>>>> NAT is bad for port 
>>>> forwarding and I wouldn't recommend it, it can
>> be done,
>>>> however you must 
>>>> be sure the two private ranges are not
>> conflicting.  In
>>>> other words, if 
>>>> the device doing NAT sees the same network on each
>> side, it
>>>> will get 
>>>> confused.  If this is the case, do something like
>> this.
>>>> INET <----> 2WIRE-DSL
>> <--(192.168.1.0/24)-->
>>>> WIFI-RTR 
>>>> <--(192.168.2.0/24)--> END-USERS
>>>>
>>>> You will still have double NAT in place, but this
>> should
>>>> allow 
>>>> connectivity to 192.168.1.254 (your DSL box). 
>> Because this
>>>> IP address 
>>>> only exists on one side, your WiFi router would
>> treat it
>>>> like a "public" 
>>>> IP and translate it just fine.  Feel free to use
>> any of
>>>> these networks 
>>>> as they are all reserved for private use.
>>>>
>>>> 10.0.0.0/8 (10.0.0.0-10.255.255.255)
>>>> 172.16.0.0/12 (172.16.0.0-172.31.255.255)
>>>> 192.168.0.0/16 (192.168.0.0-192.168.255.255)
>>>>
>>>> However, the best approach would be to directly
>> connect one
>>>> PC to your 
>>>> DSL box (via DHCP), login and disable NAT, connect
>> your
>>>> WiFi router back 
>>>> up, reboot both DSL and WiFi router (in that
>> order), then
>>>> login to your 
>>>> WiFi router and verify for its public address that
>> it does
>>>> NOT have an 
>>>> IP address which falls in the ranges given above.
>>>>
>>>> One more thing to mention, most DSL routers will
>>>> automagically disable 
>>>> NAT once they see a connection to the
>> WAN/DSL/Internet
>>>> side.  In this 
>>>> case, your network should be fine.  Simply
>> disconnect the
>>>> DSL box from 
>>>> the phone line, reboot it and you should get
>> connectivity
>>>> to 
>>>> 192.168.1.254 for management purposes.  Once
>> plugged back
>>>> in to the 
>>>> phone line, connectivity to 192.168.1.254 will go
>> away. 
>>>> However, to do 
>>>> this, I would plug a PC directly into the DSL box
>> to avoid
>>>> network 
>>>> confusion if you WiFi router uses the same network
>> as your
>>>> DSL box (as 
>>>> stated above).
>>>>
>>>> Hope this helps, if not, please enlighten me on
>> your
>>>> network setup as 
>>>> there are too many posts for me to trace back on
>> ;)
>>>>
>>>>
>>> Honestly, Luke, I have no idea what you mean at the
>> beginning
>>> of your reply so let me try to explain.  Two machine
>> LAN.  Outside
>>> world connected to 2wire DSL router/ modem combo. 
>> Router wired
>>> to new Gateway Intrepid machine which is now in shop
>> so I have no
>>> hard wired maching in place currently.  The other
>> machine in anther
>>> room has a syslink wmp54g wifi card installed and a
>> NIC also but
>>> not connected to anything.  The eth0 interface is
>> setup with same
>>> IP as the wifi.
>>> I don't know about NAt either and If I understand
>> what you said
>>> I don't have a separate router and modem.  They
>> are all in one box,
>>> a 2wire 1701hg router/modem combo.  I've only had
>> experience 
>>> with this one router.modem combo.  it seem that you
>> refer to
>>> each separately above, but I'm not sure.  In any
>> case, I'm about
>>> to move the wireless machine and hook it up directly
>> to the
>>> router/modem(after unplugging it to reset) and start
>> the machine
>>>  back up under DHCP to see if I can connect to
>> 192.168.1.254 and
>>> access the 2wire setup page again.  Hope this explains
>> a liitle.  I
>>> know what you mean, I've been answering replyies
>> on this issue all
>>> day and haven't had time to move the machine or
>> switch back to DHCP
>>> yet but will do so now.   Thanks for you input.  Sorry
>> I didn't uderstand
>>> most of it but I did say I was a network idiot in an
>> earlier post.
>>> Leonard Chatagnier
>>> lenc5570 at sbcglobal.net
>>>
>>>
>>>
>> No, problem, that does clear some stuff up so ignore the
>> bulk of my last 
>> reply.  So to clarify, you have (right now) one PC
>> connected via 
>> wireless to your 2Wire DSL.  You can connect to the
>> Internet just fine, 
>> but cannot connect to the 2Wire?  Try this command...
>>
> That's correct.
>  
>> [luke at Ignignokt ~]$ netstat -nr
>> Kernel IP routing table
>> Destination     Gateway         Genmask         Flags   MSS
>> Window  irtt 
>> Iface
>> 10.188.39.192   0.0.0.0         255.255.255.192 U         0
>> 0 
>>   0 eth0	<-- My local network.
>> 169.254.0.0     0.0.0.0         255.255.0.0     U         0
>> 0 
>>   0 eth0	<-- If you have this as well, ignore it.
>> 0.0.0.0         10.188.39.193   0.0.0.0         UG        0
>> 0 
>>   0 eth0	<-- My default gateway.
>>
>>
>> See where I have "10.188.39.193"?  That is my
>> default gateway hence the 
>> "G" flag.  In your case, is yours 192.168.1.254? 
>> If it is something 
>> different, that is most likely the IP address of your
>> 2Wire.  Try 
>> connecting to whatever IP address is listed there in
>> Firefox.
>>
> I have attached the output but it still says my gateway
> is 192.168.1.254 which is what it's supposed to be 
> the 2wire 1701hg router/modem.  Thanks for trying.
> 
> lchata at ubuntu:~$ netstat -nr
> Kernel IP routing table
> Destination     Gateway         Genmask         Flags   MSS Window  irtt Iface
> 192.168.1.0     0.0.0.0         255.255.255.0   U         0 0          0 eth0
> 192.168.1.0     0.0.0.0         255.255.255.0   U         0 0          0 wlan0
> 169.254.0.0     0.0.0.0         255.255.0.0     U         0 0          0 wlan0
> 0.0.0.0         192.168.1.254   0.0.0.0         UG        0 0          0 wlan0
> 0.0.0.0         192.168.1.254   0.0.0.0         UG        0 0          0 eth0
> lchata at ubuntu:~$ 
> 
> Leonard Chatagnier
> lenc5570 at sbcglobal.net
> 
> 

I see you have duplicate entries, one for eth0 and one for wlan0.  Are 
both these interfaces currently up?

Send the output of "ifconfig -a" please.  Also, what is each interface 
using?  DHCP or are they static'ed, or one of each?

-- 

Luke J Militello, CCNA
Network Engineer
Technical Operations
Charter Communications
Cisco Certified Network Associate
Michigan Technological University, BS
Computer Network & System Administration




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