Re: best practice for advertising peering fabric routes

[Niels Bakker <niels=nanog () bakker net>]

* 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.

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