This one caused a friend some headache when setting up a switched internet connection which had zero padded IP addresses in the configuration paper like so:
No matter how he tried to configure the Mac network stack, it just didn't work. But the GUI also didn't complain about errors.
I later found out that pinging these zero padded addresses in a terminal showed "unable to resolve" while pinging the same address without padded zeros (
192.168.019.254) showed "unable to reach" which brought much light into this mysterium. Removing the useless zeros made everything work.
Is this a bug or a feature? I never experienced such strange behaviour before - no matter if I use the GUI or CLI to configure or test IP stuff.