[drug5]

Interesting. How is this encoded?

[tirpen]

It's just the bits of the ip number interpreted as one 32-bit integer instead of four 8-bit integers.

[vimda]

It's a decimal encoding of 0x01000001 - 1.0.0.1

[OrangeMonkey]

Its A.B.C.D with A255^3 + B255^2 + C255^1 + D255^0.

[tirpen]

Almost. Replace all 255 with 256 in the formula.