They have a list of certified modems.

https://www.cox.com/residential/support/cox-certified-cable-...

I had a bit of an issue with such a modem. It took a couple of support chats calls to get it going but it's been fine ever since. I did seem to be related to the MAC, but the expectation was that it should have just worked.

I just got a new Motorola MB8600 modem which is on their list. I swapped modems, called support and gave them the model and MAC address. It took about 10 minutes total. Very painless.

Just a heads up: if you’re asking these questions, you might want to reconsider until you understand it more.

You’re going to need: A new modem A new router

You’ll need to talk to Cox and give them the HFC ID and Serial number.

Then, you’ll need to connect everything, and configure your router so that it’s secure.

That’s a nebulous word, ‘secure,’ because my security might be different than yours, but you’ll want to make sure the router is locked down so outside attacks are avoided, and the neighborhood isn’t using your services.

So, take that in consideration.

> you’ll want to make sure the router is locked down so outside attacks are avoided, and the neighborhood isn’t using your services

What are some key settings you would recommend to prevent these exact things? It's a bit challenging to grok all of the advanced router settings, and I don't think mine comes with "locked down against outside attacks" presets.

One of the big ones is upnp port forwarding. Your router might call it something else, but it's essentially a way for software to request a port forward from your router. This sounds alright at first but it's frequently abused to allow stuff that shouldn't be publically accessible bypass any firewall. The biggest issues with it is that it's completely unauthenticated so with the right commands sent, an attacker can cause anything to be exposed. Port forwarding alone isn't a bad thing, but the automated unauthenticated setup is just usually too much.

I had to mess with some settings [1] to get my OpenWRT router to work, but my TP-Link modem works great.

[1] https://alexplant.org/post/openwrt-cox/

In my experience with Cox, you simply plug it in and it just works. It might take a little longer to initialize with a new MAC, but I've never had to call or notify them of a modem swap.

Yes, usually it is that simple. Sometimes you can just plugin the modem and switch it yourself using your browser or their mobile app.

I just bought a modem and then started service on the website. I never had their modem in my house.