DHCP after short disconnection and reconnect within 10s

[ben]

Hi!
I think I know that a Windows DHCP client will no reconfigure its
DHCP/Auto-IP configuration if a disconnection lasts less than 10 seconds. In
such a case it immideately uses the "old" configuration.

1) Is that true?
2) Where is that behavior documented?

Thanks for your help,
Ben

 

[Richard G. Harper]

Actually, in a DHCP environment, the client will generally always ask for
the last IP address it was assigned and will get it if that address is
available. Use Google and you will find mountains of documentation on how
the DHCP negotiation process works.

 

[ben]

Thanks for your response!
I know what is written in the RFCs. You are right, a client tries to get the
old address first.

But the question is whether there is a minimum time the link has to be
disconnectet for the client to start the DHCP again.

Reason actually is a scenario without DHCP
--> The client tries DHCP for one minute. Auto_IP will be assigned then.
--> The link is disconnected for lets say 5 seconds

----> Does the client then again tries for one minute again and then starts
Auto-IP again? Or does the client tolerate short disconnections and then
assumes that he can just use the old config without verifying it...

Thanks in advance,
Ben

 

[Phillip Windell]

I've never worried about it enough to try to prove it, but it seems that any
disruption causes the whole process to repeat. This can be seen by moving a
patch cable to another switch port that is another subnet. Even if you are
really really quick with it the client will still
"disable",.."re-enable",..."re-aquire",...and get an IP# from the new subnet
as long as the DHCP environment is working correctly. At least is does with
Windowws XP or newer,...don't know about older OSs or Linux-ish OSs.

--
Phillip Windell
www.wandtv.com

The views expressed, are my own and not those of my employer, or Microsoft,
or anyone else associated with me, including my cats.
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