I have a Raspberry Pi 3 B+, with the built-in wifi adapter (wlan0).
I wanted to have another USB Wifi adapter (Alfa AWUS036AC) attached to it, and connect to the same network. I followed the tutorial here, and (wlan1) is up successfully.
However, after doing so, the in-built wifi adapter is down.
I want a Pi router - so, one adapter serves as an access point, while the other is connected to my home router. Nevertheless, I'm curious as why wlan0 is able to connect at the start with /etc/network/interfaces being empty.
So, I have 2 questions:
What could have caused wlan0 to be down?
I realised that at the start, /etc/network/interfaces is empty. So, how is it possible for wlan0 to connect to the network successfully? For wlan1 to connect, I have to modify this file.