On a Windows 2000 PC, I did a "ipconfig /release" to disconnect it from the network. After about 6 hours, I checked it again and it was still disconnected. But then about 17 hours after that, I checked it again and it had renewed the IP address and was back on the network. I never did a "ipconfig /renew", so is Windows supposed to renew the IP address automatically some time after a "ipconfig /release"?

Or could there be some malware on this computer that detected it was off the network and renewed the IP address? (My ISP emailed me saying it detected malware on one of our computers so I am trying to figure out which computer it is.)

  • 1
    Had you woken/restarted the computer during the 17hrs? Either would possibly prompt Windows to wake the NIC and renew an IP...
    – Kinnectus
    Jul 22 '14 at 7:00
  • @BigChris This computer doesn't go into sleep mode, and it was powered on the entire 17 hours. Windows is also configured to not put the NIC into any power saving mode. Jul 22 '14 at 7:05
  • You could try to check event log about events from NIC.
    – montonero
    Jul 1 '19 at 14:58

Firstly, if you are trying to figure out which computer is infected with the malware, then you are on the wrong path. You should use special tools for that or monitor your processes, rather then guessing if PC reconnected to the network.

Answering your original question - PC is not supposed to be automatically renewing IP config after it has been released. However if you are using WiFi and you lost connection for a short period of time (which happens now and then) it might do the whole reconnect process which will include release, renew and flushdns.

  • Yes I am running malware scanners on all computers. But I was curious if Windows was supposed to automatically renew the IP or not. This computer is directly connected to the router via ethernet, so I wonder why it reconnected. Jul 22 '14 at 7:44

Could be anything, because we can't guarantee there was no interference in the state of the machine between the computer executing your command and you coming back to check if it has an ip.

To answer your question, ipconfig /release does not have an option to change the timer, create a timer or remove the timer. A timer is not even mentioned in the documentation for ipconfig /release

Ipconfig doesn't do much except manipulate your tcp/ip stack and display your tcp/ip configuration. Its meant for troubleshooting and has many useful functions that do exactly and only what they say.

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