best practice for advertising peering fabric routes

Niels Bakker niels=nanog at
Wed Jan 15 20:50:14 UTC 2014

* bill at (William Herrin) [Wed 15 Jan 2014, 19:27 CET]:
>On Wed, Jan 15, 2014 at 12:54 PM, Niels Bakker <niels=nanog at> wrote:
>>* nanog at (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,

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