Wireshark
Just the other day, I had to prepare a simple NAS box for providing off-site FTP storage in the datacentre. And then I realised I couldn’t remember the IP address and username and password. Oh my gosh… how am I gonna get in?
And then I recalled the software package Wireshark. Fantastic piece of software, started showing all the packets that’s being broadcast, and then I saw the IP to connect to. Found that all settings had been reset, which meant I could use the default username and password to get in to start setting it up. Lucky!
Linux is wonderful - (almost) everything is available free, and documentation and others’ past experience is but a few Google/forum clicks away.