I thought I knew TCP & UDP/IP but I was reminded this week about the 188.8.131.52/4 multicast subnet. If you’re ever in a position where you need to identify a device’s IP address (even on a different subnet, but the same LAN segment) you can PING 184.108.40.206 and everything on the segment will respond to the PING (firewall settings permitting).
You can see that all the machines on the 10.100.100.0/8 network respond.
This comes in very useful with Amulet DXiP cards which you configure over a web interface. Our demo kit came back from a customer who had forgotten what they had hard-set the cards’ IP addresses to and this technique was a life-saver.
Thanks for reminding me of this Graham and Don Poves!