homelab

depends on what you mean by "do anything". I've managed to shed several ms of latency by doing a modem delete.

My two favorite stories of this were for the local DSL/fiber provider here in Canada, Bell. They use vDSL2, and GPON/XGS-PON respectively. In the former case, I set up a node at my house, which was a Cisco ISR router, with a vDSL2 EHWIC card installed; after some work, I managed to get the unit dialing into the internet via PPPoE, and I managed to drop about 5-10ms of latency simply by removing the ISP provided garbage. It was also clean... a single phone cable plugged directly into the router, and out the other side was a switch, which provided all the network connections I required.... my setup was a tiny bit more complicated than I'm explaining, but the other details don't really matter (long story short, I was operating on a Bell line through a wholesale client (third party ISP using Bell's "last mile"), and they provided me with a /29 subnet for internet routing - the Cisco handled the WAN to WAN communication, and on my /29, I had a few devices including my primary firewall, which was between me and the internet, that then broke out onto a switch for everything to connect to.... a bit more than the average joe can handle, but I work in networking). The other story is about their GPON; I managed to figure out that their GPON interface is almost entirely unprotected, and worked with a G-010S-A (a fairly common design from Nokia, but has variants from other major vendors that are largely the same), so by buying or otherwise obtaining one, and programming it very specifically, you can actually plug the SFP GPON module directly into a router, and with some clever configuring, get your PPPoE to work across it without too much trouble. There's plenty of info about it online if you want to see more.

The only sad story I have about this is that Bell started to release a new modem that has a built in fiber module (no longer using the G-010S-A), which is compatible with both the GPON and XGS-PON systems; I have yet to find an XGS-PON version of the G-010S-A that I can use for the purpose. A friend of mine, whom I did a modem delete for with the G-010S-A, was in an area that was originally served by GPON, so the solution worked. After some time though, Bell implemented XGS-PON in his area, and actually removed compatibility for the GPON, so the solution stopped working. Until I find an XGS-PON equivalent to the G-010S-A, I'm at an impasse. In the interim, my friend has put his modem back in-line, and IIRC put it into bridged mode, which is second best to a modem delete.

I'm a network technician/engineer as my dayjob, so working with this stuff is entirely in my wheel house, I can usually give useful advice for anyone wanting to walk in my shoes to delete their modem, and make it simple enough that it doesn't require my level of skill to maintain (like in the case of my friend), and advice/strategies about how to handle the ISP.

CG-NAT is entirely in the ISP hands, I cannot touch their fancy CG-NAT engine or route around it. My best advice for anyone facing down CG-NAT, is to use IPv6, if your ISP supports it. Simply put, the best argument I've seen for IPv6 adoption is CG-NAT. NAT itself was bad enough, but CG-NAT is a whole new level of evil; it breaks so many things. IPv6 takes you back to the old days of globally routable addresses, end-to-end, completely eliminating the need for any kind of NAT. A large portion of the internet uses/supports IPv6 already, pretty much all the major data carriers support it and actively use it for their own gear (people like google, facebook, apple, microsoft, cloudflare, etc). IPv6 shouldn't be feared, as an end user, the whole thing is going to behave exactly as you expect it to. The trick is: getting it up and working on your LAN, once you can work that out, you're laughing.

Likely won't change CG-NAT config, the new modem would still have to get its IP address from the attached ISP