Re: Trouble obtaining IP address
- From: "Chuck [MVP]" <none@xxxxxxxxxxx>
- Date: Thu, 31 Jan 2008 08:24:10 -0800
On Wed, 30 Jan 2008 09:07:02 -0800, Dual Trace
<DualTrace@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
"Chuck [MVP]" wrote:
On Tue, 29 Jan 2008 11:38:05 -0800, Dual Trace
<DualTrace@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
"Chuck [MVP]" wrote:
On Tue, 29 Jan 2008 08:52:32 -0800, Dual Trace
<DualTrace@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
I?ll try to make this as short and clear as possible and then reply with
details as needed / requested.
I have an old computer connected to internet via DSL modem which used to
work fine. Decided to connect a new computer to internet using the same
modem, so I moved the Ethernet cable from the old one to the new one. The new
one was not able to get the IP address. Went back and forth through the
ipconfig deal with Verizon tech support, but could not make it work. Tried
the same maneuvers with the old one, just to prove modem and connection are
fine and indeed everything worked fine when the old computer was hooked.
Tech support from the new computer (HP) advised me to go through the system
recovery because some Windows socket registry might be corrupted. Done the
recovery and was able to connect the new computer. IP address, etc. were
acquired and all was OK.
Now I switched the Ethernet cable to the old computer again and guess what:
it shows the same symptom. Cannot obtain the IP address. Verizon tech support
said I cannot switch Ethernet cable from one computer to another and expect
to work because the last computer obtaining an IP address will somehow keep
that route occupied and the attempt of another one to get an IP address will
fail. They said I need a router.
Well, how come it worked after restoring the new computer? At that stage of
the game, the old computer had obtained an IP address and then the new one
was able to connect and get his as well.
Note: When trying the ipconfig command, both IP and Subnet Mask seem to get
valid addresses, but none is shown for Default Gateway.
I know this is not black magic, but it certainly looks to me.
Any help is appreciated.
Thank you,
Dual Trace
You do need a router. I'm surprised that an ISP would actually tell you that,
though.
Switching two computers back and forth using the same Internet service is a
dodgy process. With some services, it will work, with others it may work but
take time for one computer be accepted after another was used previously.
<http://nitecruzr.blogspot.com/2005/07/connecting-different-devices-to-your.html>
http://nitecruzr.blogspot.com/2005/07/connecting-different-devices-to-your.html
My guess is the amount of time that it took you to run the Winsock repair was
enough time for the one MAC address to clear from the Verizon DHCP server, and
allow the second address to work. You can't tell though for sure. Only Verizon
can tell you, if they will.
Get a router, they are not expensive and they will help you in many ways.
<http://nitecruzr.blogspot.com/2006/01/proper-network-design.html#Router>
http://nitecruzr.blogspot.com/2006/01/proper-network-design.html#Router
Chuck,
Very interesting reading in your links. So some internet providers will not
let you switch from one computer to another without waiting some amount of
time. Then it looks like the new computer would have been able to get the IP
address even without the Windows recovery job, just by waiting long enough
before attempting it. You know, I tend to think this ?conspiracy? theory
applies.
No conspiracy. Just how DHCP, and DHCP leases, work. Until a lease expires,
your service isn't going to need a new IP address. That lessens the load on the
DHCP server. Unfortunately, since your computer (if that's what is connected to
the modem) has a different MAC address than the device that was previously
assigned the IP address, its MAC address won't be recognised. Since the IP
address for your connection was already assigned, you don't get another.
MAC addresses is a Layer 2 identity, and DHCP / IP is a Layer 3 identity. This
is just how the layers work.
<http://en.wikipedia.org/wiki/OSI_model>
http://en.wikipedia.org/wiki/OSI_model
Chuck,
Understood. What I don?t understand then is how come three different tech
support guys from Verizon spent a total of more than 2 hours with me going
back and forth through various schemes instead of telling me about the real
issue. Were they that dumb? I thought conspiracy is more plausible.
And by the way, last night I plugged again the old computer and it acquired
an IP address and worked fine. So the waiting period rule applies. Then I
spent all evening moving Outlook files from one to another etc. and this
morning I plugged the new computer and it got connected with no problem.
Verizon Tech Support is not known for employing, consistently, the most
technically knowledgeable staff. You were helped by those who are less
technically knowledgeable.
The folks that you talked to aren't the ones that actually maintain the DHCP
servers, and it's always possible that the two groups don't communicate. Which
is one of the advantages of getting help here, or in DSLR Forums.
<http://www.dslreports.com/forum/sharing>
http://www.dslreports.com/forum/sharing
Anyway, I'm glad that we were able to help you sort the problem.
--
Cheers,
Chuck, MS-MVP 2005-2007 [Windows - Networking]
http://nitecruzr.blogspot.com/
Paranoia is not a problem, when it's a normal response from experience.
My email is AT DOT
actual address pchuck mvps org.
.
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