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Inconsistent DHCP Connectivity on Lenovo

Posted on 2011-09-08
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Last Modified: 2012-05-12
I have a Lenovo laptop that was set on DHCP and could not get an IP address.  We tried it in several locations to eliminate it being any software or hardware issues and determined there was an issue in the laptop itself.  We ran a Malware scan which came up clean and WinSockXPFix.  We were then able to get an IP address through DHCP.  Upon taking the laptop back to the business, we put it on it's docking station, turned it on and no IP address through DHCP.  I removed it from the docking station and plug the cable in directly to the laptop, restarted the computer and still no DHCP.  I then checked the port on the switch.  It appeared to be OK.  I then took the laptop back to the server room and took a cat5e cable with me and plugged the cable into the switch directly and then into the laptop.  I DID get an IP address through DHCP.  So, then I used the same port that was being used in the customer's office.  Plus into that port with the same cat5e cable, restarted the laptop and I DID get an IP address.  I then took the laptop back to the office, set it on the docking station.  No IP address through DHCP, however I set a static on the laptop and we get internet and network both.

I am very puzzled as to how we are getting an IP address through DHCP at every location we tested except in the one location, however that same exact spot/cable works with static IP.

The same customer took his laptop to his other office and exact same office there.  These two offices are connected via a full-time VPN connection.
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Question by:sahinman
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Expert Comment

by:Ackld2008
ID: 36506397
HI there,

I am not trying to offend your intelligence but you said "Upon taking the laptop back to the business, we put it on it's docking station, turned it on and no IP address through DHCP". Sometimes you need to do ipconfig /release then ipconfig /renew.

if you run ipconfig /all you will find how long the lease for DHCP is for. If you take away your laptop from one network and plug to the other, the IP address still keeping the old one. The trick is some laptops does not automatically send a DHCP request to DHCP server when it has the non expired IP address from previous network.

So again, the trick will be ipconfig /release and ipconfig /renew.

Please try and let me know.

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Expert Comment

by:riteheer
ID: 36506740
what version of windows?
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Expert Comment

by:Rob Williams
ID: 36512633
Might it be Vista? And is the DHCP server at the problematic site a router or server?

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Author Comment

by:sahinman
ID: 36512845
Windows XP Pro - this laptop/network combination has been working for over a year without any problems, this problem just started recently
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Assisted Solution

by:Ackld2008
Ackld2008 earned 167 total points
ID: 36512989
Quote " I then took the laptop back to the server room and took a cat5e cable with me and plugged the cable into the switch directly and then into the laptop.  I DID get an IP address through DHCP"

Did you actually use the same port on the switch where it link to your docking station? Did you use patch panel? What switch do you have there? Can port security be assigned to only 1 mac address to which ever laptop plug to the port first. Remember if it is cisco switch there is a feature to block other laptop to access to the switch.
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Assisted Solution

by:riteheer
riteheer earned 167 total points
ID: 36514094
open up a command prompt and then type:
netsh int ip reset c:\resetlog.txt
This will reset the tcp/ip stack,  it will also create a txt file of the changes that were made, if any.... post this file here please.
Also, download hijackthis from here:  http://hijackthis.de    use the direct download button in the top right hand corner of that screen.
after downloading, run it and save the log file. post the log here please.
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Assisted Solution

by:Philonator
Philonator earned 166 total points
ID: 36517857
Any chance that access connections is switching your "locations" on you and incidentally blocking connections?  I would update it first using thinkvantage or lenovo update.
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Accepted Solution

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sahinman earned 0 total points
ID: 36523234
Solution found. There was a small switch behind the desk that was causing the problem. When I reset the switch the DHCP work immediately. I did not even know the switch was there.
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Author Closing Comment

by:sahinman
ID: 36553454
All were good suggestions.
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