Careful thought should be given into whether the BGP community means "this is an anycast prefix" vs "please hot-potato to this prefix". Latency-sensitive applications may prefer hot-potato to their network even if it's not technically an anycast range, as their private backbone may be faster (less congested) than the public internet.

Damian

On Tue, Mar 19, 2019 at 10:57 AM Siyuan Miao <aveline@misaka.io> wrote:

A Well-known BGP community will be better.

You'll need to rewrite next hop or do something similar if AnyCast prefixes are learnt from a multi hop BGP feed, and it made the configuration more complicated and difficult to debug.

On Wed, Mar 20, 2019, 01:48 Fredy Kuenzler <kuenzler@init7.net> wrote:
Am 19.03.19 um 18:39 schrieb Bill Woodcock:
>> On Mar 19, 2019, at 10:12 AM, Fredy Kuenzler <kuenzler@init7.net>
>> wrote: I wonder whether anyone has ever compiled a list of
>> well-known Anycast prefixes.
>
> I don’t know of one.
>
> It seems like a good idea.
>
> BGP-multi-hop might be a reasonable way to collect them.
>
> If others agree that it’s a good idea, and it’s not stepping on
> anyone’s toes, PCH would be happy to host/coordinate.

Thanks for the effort, much appreciated.

Am 19.03.19 um 18:40 schrieb Joe Provo:
> I think one would want that internal and no rely upon someone else
> maintaining it. You might check if Oracle followed up on the
> Renesys/Dyn work documented:
> https://dyn.com/wp-content/uploads/2014/07/NANOG59_Anycast.pdf
>
> ...where there were ~600 anycast v4 prefixes at the time.

That's a lot %-]

Maybe a well-known community (similar to RFC7999) could be defined and
every Anycast operator could tag his prefixes? That's likely a better
idea than manually maintain some list somewhere.

--
Fredy Kuenzler

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