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PC connects from different locations, but not from home

Posted on 2004-08-24
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Last Modified: 2013-12-14
Dell Dimension 4500
P4-2.0
256MB RAM
Windows XP Home, Internet Explorer 6.0

Customer unable to connect via ADSL to the Internet (modem only, no router).Upon inspection found the following:
- ADSL properly configured for dynamic addressing.
- Ipconfig revealed that it was pulling an ip (216.86.126.254) which is part of the ISP's range of ip's.
- PC couldn't connect or ping anything.
- Ipconfig/release and ipconfig/renew would not clear this ip. Performing an ipconfig/release and then shutting off the pc overnight and renewing the ip the next day still resulted in pulling the same ip and the connection would continue to fail.

Ran antivirus and spyware scans, reset tcp/ip stack, deleted and reinstalled all network-related stuff, etc., etc. Still no joy.

Now here is what is bizarre:
- I took this pc back to my shop and connected it to my ADSL connection and it pulled a new ip and connected immediately using the customer's ADSL modem.

- I then took the pc to the ISP's office and connected directly to their equipment and again it pulled a new ip and connected immediately.

- Returned to client's premises and reconnected pc, but it reverted to pulling the original ip and failed to connect.

- Replaced the ADSL modem and it still pulled the same ip and failed to connect.

- Called ISP tech support and had them monitor the connection as I attempted to connect. According to tech support, it was the client's pc that was requesting this ip, but the server refused to assign it (probably because it was in use).

- ISP put in a trouble ticket to the telco. Telco responded by rebinding the path and eventually changing to a different port. Still no resolve.

- I brought in my own test PC and connected it to client's ADSL equipment on their premises. My pc pulled a different ip and connected successfully.

How can this customer's pc pull new ip's and connect fine from different locations, but pull the same old ip and fail to connect only when attempting to connect from home???
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Question by:rball
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by:dis1931
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Not sure how the service provider does it but many times providers give out IP addresses based on MAC address.  So everytime the ISP sees the MAC address it gives the same IP....looks like a ISP issue....if you change the NIC and use a different one it will most likely work fine.  I would contact my ISP again if I were you and make a big stink about it...make sure you talk to a level2 or 3 tech not the first person that answers the phone...they are helpdesk at best and usually only phone operators trained to pass along issues....make them send you to a knowledgeable person...

Dis
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by:rball
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Appreciate your help Dis, but I'm afraid that isn't it. The pc is set up to connect dynamically, meaning it is assigned a new ip every time it connects as opposed to a static ip as you suggest. This pc performs properly at two different locations (pulling different ip's as it's supposed to) but when connecting from home it suddenly seems to think it must request an ip in static fashion.

rball
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by:dis1931
dis1931 earned 100 total points
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No i didn't say it was a static IP....you misunderstand....ISPs like to record MAC addresses on their side of the fence or on their cable modems or equipment...once they identify a mac address they may only want to distribute a certain IP to it....despite your IPCONFIG release and renew...hence the same IP....I have a provider that gives dynamic addresses as well but my IP address hasn't changed in the last year despite several disconnects, being off for a few days at a time, etc...even after rebuilding system with different OS, etc....the point is this is held on ISP side and they may need to be involved in this issue....this is different from when an ISP assigns you a static IP and this is the only one you use....that is not what I am suggesting...

Dis
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by:rball
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I've already had extensive contact with the ISP, Dis, at all levels of support. They assure me that they are not the one's assigning this ip. If they were assigning the same ip to the mac address of the network card, then why does it get a different ip when the computer is moved to a different location? Therein lies the mystery.

rball
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by:dis1931
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sorry, i re-read your posting...and yes you are right about this...i didn't realize when you went to other locations you were using the same adsl modem and same provider as well as the same PC.  However, you have re-iterated that it must be the ISPs issue.  You have ruled out the ADSL modem.  You have ruled out the PC and NIC.  So what else is left other than the line and the configuration for his location...it should be on the ISP side that is my hunch...If all the equipment works fine then what else is there....

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by:
Fatal_Exception earned 400 total points
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Personally, it is just to easy to install another NIC into that box and see if you still get the same IP address.  This would be the first TS step I would take here.  You could also reset the winsock stack just as an easy next step (although I don't think this is the problem..)  Use this utility for the reset:

http://www.spychecker.com/program/winsockxpfix.html
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by:JonSh
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I agree with Fatal's troubleshoot steps above, but I'm going to add something.  Try replacing the Ethernet whip between the modem and PC first.  I'm assuming this isn't a USB connection......

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by:rball
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I've already swapped the cable between the ADSL modem and the nic. Also replaced the phone line. Also temporarily unplugged every phone in the house and removed all filters.

I'm going over there right now to replace the nic and give the winsock utility a shot, although I have already gone through the winsock thing manually. I'll post results when I get back.

Thanks all,

rball
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by:Fatal_Exception
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Good luck!!!
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by:rball
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O.k., here's what happened:

Ran the winsock utility - no success. However, this utility is pretty cool so it's going into my 'toolbox'

Swapped out the nic for another one - success!!! Yeah, I know - I should have done this right away. But it worked at two other locations which meant it was functioning properly.

I suspect that dis1931 may have been correct when he suggested that perhaps the ISP, for reasons only known to them, was assigning a particular ip to this nic's mac address. However, that doesn't explain why the same pc worked fine with the same ISP when connected from a different location. In the end, it seems that a combination of mac address + customer's phone number (location) = assigned the disfunctional ip number.

So here's how I've decided to divide the points:
100 points to dis1931 for his suggestion, although we'll never be able to prove it.
400 point to Fatal Exception for the solution that finally resolved the problem, although we'll never know why.

Thanks all,

rball

 
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by:Fatal_Exception
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Just an observation..  It could be that when you moved the system to another location, the routing was different and it 'looked' like a new connection, or it could be that the router which is verifying the MAC address was different when you moved it.  That is kinda why I suggested another NIC...  just to be sure..

Glad you got it, and hope your customer is happy..  :)

And thanks..

FE
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by:Fatal_Exception
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Oh.. and one more thing just so you know what that winsock fix does...  (nice to know what is going on in the background, eh?)

. It disables all network adapters
. It removes the registry keys Winsock and Winsock2
. It replaces the keys with a virgin registry set from a clean install of XP it contains inside the program
. It forces a rebuilding of the Winsock service, including routing tables, using the Netsh int ip reset resetlog.txt command
. It re-enables your adapters
. It checks that your HOSTS file has a valid localhost pointer to 127.0.0.1

FE
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Author Comment

by:rball
Comment Utility
Great little utility. I can't beleive the time this will save me when troubleshooting XP connection issues.

Thanks,

rball
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by:Fatal_Exception
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No problem..  we have tons of these utilities..  In fact if you wish to visit my website, and the suggested links, you will find lots of good things you may find useful...  Bootable CD's such as Barts, for instance, are things that every tech should carry with him (or her)..  

Feel free to look around here:  www.doverproductions.com

BTW:  I am not a web designer, as you can see when you go there, but I try..  :o)

You may also get a kick out the MAC attack link under Misc.  Just a little MAC humor in a flash presentation..  

FE
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by:rball
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Lots of interesting stuff, but all you Mac haters just have to see "MAC Attack"
Been there & done that!

rball
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by:Fatal_Exception
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:)  
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