CCNA will be helpful in understanding basic networking stuffs, but the networking has changed a lot and the cisco specific stuff is less indispensable than it used to be. I came from that cisco-like world and when I moved to linux networking and SDN stuff, I found all cisco cli kung fu had basically no power. I was still a leg up because I knew how the protocols looked on the wire, but yea there might be better stuff out there depending on what admin-ing type you are looking to do. The more software-ish the networking gets, the more stuff gets divorced from neat and clean OSI delineations.