

I dunno if they still offer it, but I found that Cisco’s ICND1 was fairly neutral. They use examples from Cisco stuff, naturally, but the majority of the content is around learning and understanding how IP networks function. This is the first half of the CCNA study materials, and honestly, one of the best resources I had, and used, for learning how it all works.
There’s probably a ton more out there now, but at the time when I was learning, it was all CBT Nuggets and pluralsight… I believe a lot has hit YouTube in recent years.
Don’t worry if the information is out of date, this stuff doesn’t change. The updated stuff just has newer vendor specific information, and IPv6.
IPv6 isn’t crazy different in how it behaves, but the mechanisms for local discovery, IP assignment, and whatnot, can vary quite extensively.
Good luck out there
So, in my case, I had a modem router model by a company called SmartRG. Details aside, I pretty much instantly put it into bridged mode so it wouldn’t participate in the IP routing. That modem did modem things only.
The connection went from provider phone line to SmartRG to my firewall.
I was weird and got a set of WAN IP addresses, so I put a router in front of everything to handle that, so the connection went from provider line, to modem, to router, to firewall.
It’s not super relevant, but the router I was using was a Cisco 1911. This is a semi modular enterprise router. The modular part, which will be important later, is in the form of “WIC” modules, or “WAN Interface Card” modules. The 1911 has two.
Anyways, I managed to get a WIC that supported VDSL2 with all the options and configuration that my ISP used. Happened to be the ehwic-va-dsl-m. Long story short, this module would integrate with my router and act as a modem of sorts to “translate” to the provider line. When I implemented this, I basically threw out my SmartRG. The phone line went directly into my router. So the connection was from the provider line, into my router, then to my firewall.
So the modem was “deleted”.
Another instance was for a fiber GPON line. The provider in this case, gave you a modem with a GPON connection, but they didn’t really tell anyone that the GPON interface was just a plain old SFP transceiver. So I pulled the SFP, put it into the firewall and threw out the modem. The provider line went right into their module in my firewall. The modem was effectively “deleted”
The idea of a modem delete is to remove whatever standalone device the provider has converting their signal (DSL, cable, or fiber) into Ethernet, and effectively plug that into your gateway.
It’s not always possible.
I’m currently looking for an option to do a modem delete for a local ISP that’s switched to xgs-pon. They put out a modem router for it that has the transceiver built in, so there’s no way to extract it and plug it into something else.
I’m hopeful I’ll find a SFP+ module like I found for the GPON ISP in my area.