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.

4 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.


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