BC Programer
Answer:Router,Modem "Gateway" Supplied by at&t. It better support wi-fi since I am paying for the service.
No problem with wired connection.
I recently switched ISP. This was a transition from DSL to cable. The cable provider (Spectrum) provided a modem/router which was wireless capable but, to get wireless working with the modem/router provided by them, I would need to pay $5 more per month. So, I thought, $5/mo is not much but it still amounts to $60/yr and I might be using this ISP for years. Also, I found I could not use my printer or any device (2nd computer) other than the computer that was connected to their modem/router when they first activated it. So, I decided to buy a modem and router; I bought a Netgear CM400 modem and a Netgear N300 WiFi router. Now, I'm back to the network functionality I had with my previous ISP; in other words, I can connect up to 4 devices (computers and printer), via Ethernet cable, to the Netgear N300 WiFi router and I have wireless access.
If your ISP is charging a monthly rental fee to use the modem/router provided by them, that would be even more reason to buy your own.
Note: before I made the change from using Spectrum's modem/router to using my own modem and router, I searched for info on doing this with Spectrum and found that they have info on their website about certain model modems they list as specific ones they recognize.