Using my 2012 Macbook Pro with Sierra, I tried to telnet into a 2014 Mac Mini inside my home. Both computers are on the NAT home-side of my Time Capsule router. For a while I was receiving a very mysterious IP address response back. Hopefully someone can help me understand why. I have the Mac Mini setup as a triple boot with Mac OS X, Windows 8, and Ubuntu 16.04 LTS. My problem was evident when the Mac Mini was booted with Ubuntu. I was able to telnet successfully a few times as shown below. But then yesterday the telnet response suggested that I was trying to connect to an address I did not specify. I listed the example below. I changed my local IP address numbers to "x" for obvious reasons. The non-x IP address is the actual unknown address reply back. Here is what happens when I am successful: Scotts-MacBook-Pro:~ scotty$ telnet xx.x.x.xx 5901 Trying xx.x.x.xx... Connected to xx.x.x.xx. Escape character is '^]'. RFB 003.008 But yesterday this was the reply for the same address above, but a different port (i.e. 5901 vs. 5900): Scotts-MacBook-Pro:~ scotty$ telnet xx.x.x.xx 5900 Trying 22.214.171.124... The connection never happened and I eventually control-C out. Can someone help me understand what has happened. I panicked a bit thinking I had been hacked and started to rip apart my Airport Express extenders which didn't fix anything. I eventually rebooted the Mac Mini, started no processes, and the mysterious response went away.