I teach a class on a software product my company makes and I find that students frequently add leading zeros to a configuration page to have the software connect to our hardware. Leading zeros are problematic in our software, that's how and why this comes up.
I always explained that leading zeros were against "the standard" thinking that's what I had been taught. As I was submitting the bug report up the chain to my engineering department, I was unable to find an authoritative source for this (i.e. "The Standard"), but I did find some interesting and related information.
Are leading zeros bad because of convention, or do they go against the standard?
This was the closest I could find to a standard to not use leading zeros, but it's an expired draft of some kind:
In the relevant section, it says:
3 Syntax and Semantics 3.1 IPv4 Dotted Octet Format A 32-bit IPv4 address is divided into four octets. Each octet is represented numerically in decimal, using the minimum possible number of digits (leading zeroes are not used, except in the case of 0 itself). The four encoded octets are given most-significant first, separated by period characters. IPv4address = d8 "." d8 "." d8 "." d8 d8 = DIGIT ; 0-9 / %x31-39 DIGIT ; 10-99 / "1" 2DIGIT ; 100-199 / "2" %x30-34 DIGIT ; 200-249 / "25" %x30-35 ; 250-255
I also found the following articles discussing the phenomenon: