Your ISP’s DHCP does not function properly

As part of my migration to the cloud, I terminated the Comcast Business internet service and switched to Xfinity internet.

When I initially signed up for the Xfinity service, I got their cable modem / router / wifi appliance. My plan was to get my own cable modem eventually because Xfinity charges $13 / month to lease the appliance.

I was at Best Buy and saw that cable modems weren’t expensive, so I decided to purchase a mid-level model (Netgear CM600) so I could save the lease fee. The CM600 would pay for itself in about 8 months.

It took a while to get setup … and there were a few false starts, but eventually I got it working connected directly to my MacBook.

I ran into a problem when I switched the CM600 over to my ASUS RT-5300 wifi router.

I kept getting the message “Your ISP’s DHCP does not function properly” on the ASUS network map page.

After messing around with it for a while, I called my friend Steve, who told me that the cable modem bound itself to the MAC address of the last device it connected to. I needed to power off the cable modem for a few minutes and let it reconnect to the router.

To test the theory, I told the RT-5300 to use the Mac address of my MacBook (clone) and it connected right away.

Eventually I reconfigured the router to not clone my Macbook’s Mac address and and rebooted the CM600 and everything was good again.

6 thoughts on “Your ISP’s DHCP does not function properly

  1. Ericka Gould

    So can anyone explain how to do what you did? I get this ALl the time with my ASUS router and have no idea how to fix it

    1. David Post author

      It should just be a mater of turning off the cable modem for about 10 minutes and turning it back on. The cable modem remembers the MAC address of device that it’s attached to for a period of time.

  2. fred smith

    Tearing my hair out today. got a new cable modem to replace Comcast’s, it worked fine with a laptop wired to the modem, but when I reconnected the router I was getting the message “your isp’s dhcp does not function correctly” no matter what I did.

    After seeing your post I entered the laptop’s MAC address into the router and voila!

    there are thousands of posts on various sites (searchable with google or other search engine) about this exact problem. what does it take for equipment vendors to become aware of this and give the right answer when someone calls in with that problem?



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