* bill@herrin.us (William Herrin) [Wed 15 Jan 2014, 19:27 CET]:
On Wed, Jan 15, 2014 at 12:54 PM, Niels Bakker <niels=nanog@bakker.net> wrote:
* nanog@shankland.org (Jim Shankland) [Wed 15 Jan 2014, 18:04 CET]:
So ... RFC1918 addresses for the IXP fabric, then? (Half kidding, but still ....)
They need to be globally unique.
Actually, they don't. To meet the basic definition of working, they just have to be able to originate ICMP destination unreachable packets with a reasonable expectation that the recipient will receive those packets. Global uniqueness is not required for that. However, RFC1918 addresses don't meet the requirement for a different reason: they're routinely dropped at AS borders, thus don't have an expectation of reaching the external destination.
They need to be globally unique because otherwise a connected network might be using them already internally, thus keeping them from connecting - or as another followup mail stated, force everything into their own VRFs, and that may still collide. This was rehashed a few years ago on the RIPE AP-WG mailing list, IIRC. -- Niels. -- "It's amazing what people will do to get their name on the internet, which is odd, because all you really need is a Blogspot account." -- roy edroso, alicublog.blogspot.com