XP and Disconnected NIC

R

RJ

I did a test at work. We use DHCP for IP addressing for our
company computers. There was some debate on how XP (Pro)
handles disconneced NICs. This is what we found out:

1. On a working PC, run ipconfig - get the ip address, subnet mask and gateway.
2. Shutdown the PC, disconnect the CAT5 LAN cable from the back of the NIC.
Boot it up, run ipconfig again - Media Disconnected is what results.
3. Plug the LAN cable back into the NIC, run ip config again. IP address
info is back.
4. Shutdown the PC, disconnect the LAN cable, for the PC, from the switch this time.
Boot it up. Again, run ipconfig. Media Disconnected is what results.

So, where does APIPA come in? According to XP Help, if a PC is setup
for automatic IP addressing (DHCP), and cannot reach a DHCP server after 60 seconds,
it will assign an automatic private IP address (APIPA). (a disconnected cable could cause this)

This is not what we saw. After several tests, sometimes waiting 5 minutes to
run ipconfig, we never got an APIPA address.

What I am thinking is "Media Disconnected" trumps everything. If XP thinks a cable
is disconnected - that's it. It does nothing else. If all cables are connected, but
it can't get a response from a DHCP server, then it assigns an APIPA address.

Yes?
 
R

R. McCarty

I think you're dealing with the MediaSense feature of 2000/XP.
It tends to unbind all protocols from the NIC. Check around the
Net there is a Registry Key you can add to TCP/IP Parameters
to turn off the Media sensing.
 

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