puppetlabs/facter — pull request #263 by daniel-pittman (2012-07-20 00:18:13+00:00)
Title: the ARP fact must die!

So, the "ARP" fact is just a fractal of bad design. You can start with the implementation, where it depends on the oldest record in the ARP cache that has not yet expired being a specific EC2 metadata server, because that is what most AMI images happen to contact first, and it presumably doesn't expire out of the cache fast.

It just goes down-hill from there. There is no sane reason to keep supporting this. We may as well have those 7.1ms back for doing something more useful with.