I've been an admin of servers and networks since I was in high school. That was about 20 years ago.
Experience with several Linux distros, initially for LAMP, currently for all kinds of applications. My experience includes not only front-end (OS, switching, routing and firewalling), but also the backend like virtualization (VMware), storage, SAN and backup. Monitoring with Nagios and Icinga. Recent admirer of the ELK stack.
I like the challenge and the diversification of spending time at any of those layers whenever necessary. Don't tell me to go sit in a corner and manage a DNS server for the rest of my life.
Experience with mail services, issue trackers like Jira and OTRS, tools like MediaWiki, etc. etc. Also had to endure Windows application packaging using some obscure tools. Performed helpdesk tasks as a student.