Used IP addresses

Anyone got some C code that loops over all used IP addresses?  Can you come up with any special optimizations?  (I need to handle them in the "%u.%u.%u.%u"-form; computations are independant and can be run in parallel)

Have you read your poignant guide today?
256.times{|i|256.times{|j|256.times{|k|256.times{|l|puts "#{i}.#{j}.#{k}.#{l}"}}}}
THIS IS SO ELEGANT FUCK I NEED TO MASTURBATE.
I've run it for an hour, currently at 1.12.90.201