DHCP Details You Didn’t Know

If you’ve been a networking engineer (or a sysadmin) for a few years, you must be pretty familiar with DHCP and might think you know everything there is to know about this venerable protocol. So did I… until I read the article by Chris Marget in which he answers two interesting questions:

  • How does the DHCP server (or relay) send DHCP offer to the client that doesn’t have an IP address (and doesn’t respond to ARP)?
  • How does the DHCP client receive the DHCP responses if it doesn’t have an IP address?


  1. Fine subject but fatally flawed by the lack of accuracy in the early article.

    Sometimes I wish I could speak and someone would listen.

  2. First - thanks for your network work for all that time.

    Let me ask again about DHCP with static binding on IOS router.
    I have origin file for the dhcp pool and I badly want to have same static IP addresses for every host no matter what we boot: windows, linux or PXE. Do You have any solution for this? How to force an IOS to treat hw address as client-id when no client-id is passed by the requesting machine?
    1. If the question is "I cannot define two entries with the same IP address, is there a way to do it", the answer is "no idea" :(
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