I’m connected to AT&T 1 Gbps fiber. I was provided with modem ARRIS NVG589. It is also a router but its features are quite limited. Moreover, I don’t want to build my home network where the core device does not belong to me.
And I decided to turn it into the dumb modem that passes everything to the router that I own and can control. In this case, I can easily switch from one provider to another without needing to reconfigure the core device. And it turns out it is quite easy. I assume the modem only handles internet traffic and does not have telephony or TV.
Firstly you need to find the MAC address for the WAN port of your router. I’m using OpenWrt and I had to go to Network|Interfaces and there I can see the MAC address. If you don’t see it, just click on the “Edit” button on the WAN interface.
Next, you need to go to your modem web interface. Typically it is at http://192.168.0.254. Then select Firewall | IP Passthrough. Then set “Allocation mode” to Passthrough. Leave “Default Server Internal Address” blank. Next set “Passthrough Mode” to “DHCPS-fixed”. And lastly set “Passthrough Fixed MAC Address” to “Choose from list” and on the right box put the MAC address of the WAN interface you found in the previous step.
Then click on the “Save” button. After that plug one end of the ethernet cable into any LAN port of the modem and the other end plug into the WAN port of your router. And that’s it. From now on, the modem will pass data directly to your router.
You can also go to Firewall | Firewall Advanced and disable everything there as your router will handle it from now on. Then go to Firewall | Packet Filter and disable packet filter by clicking on the “Disable Packet Filters” button. Then go to Home Network | Wi-Fi and disable all Wi-Fi networks.
Just in case I advise you to do these steps at a time when you can call your provider so they can fix it if you messed it up. This setup works for me for about 3 years.
I hope it helps someone.