Forum Discussion

Tutor

Jul 31, 2020

Solved

CM500 Cable Modem Creating Double NAT

Setup: CM500-100NAS on Firmware v1.01.05 Cable Modem Ethernet out to eero Gateway wireless router Xbox One five feet from router, connected wirelessly For a couple weeks, I've shown a strict NA...

antinode
Jul 31, 2020
> [...] a double NAT would mean I have NAT happening on the modem as
> well as the router. [...]

   Well, somewhere, but a modem can't do it. Another possibility:

      https://en.wikipedia.org/wiki/Carrier-grade_NAT

> [...] I'm wondering if it's something jacked up on the ISP side.

   Carrier-grade NAT would qualify.

   Have you looked at the IP address of the WAN/Internet interface on
your router? Plug that address into the form at:
https://whois.arin.net/ . Is it a public address or a private address?

inky_thoughts

Tutor

Jul 31, 2020

Final update. With the knowledge I got here, I worked with the ISP. They confirmed they use a network NAT and they needed to “open the NAT” for me. I pieced together they had done upgrades on the area which may have defaulted a previous passthrough.

After they pushed a fix, I had a moderate NAT and I could then port forward the Xbox ports to get an open NAT.

Thanks for the advice!

FURRYe38

Guru - Experienced User

Aug 01, 2020

Glad you figured it out and got it working better.

Enjoy.

inky_thoughts wrote:
Final update. With the knowledge I got here, I worked with the ISP. They confirmed they use a network NAT and they needed to “open the NAT” for me. I pieced together they had done upgrades on the area which may have defaulted a previous passthrough.

After they pushed a fix, I had a moderate NAT and I could then port forward the Xbox ports to get an open NAT.

Thanks for the advice!