Hi Jan, On 27 Nov 2025, at 14:33, Jan Zorz - Go6 <jan@go6.si> wrote:
On 26. 11. 25 09:59, Joe Abley wrote:
I seem to think normal exit selection works just fine for this in most cases, but perhaps you have seen problems that I am not aware of. What scenarios do you see where a special routing policy would make things better? Khm... We had a case where we announced our anycast prefixes to our upstream in Johannesburg and that upstream was a paying customer of a large tier1 (that we all know... :( ) and due to the fact that that tier1 received prefixes from a paying customer thye got higher preference
I have helped deploy a number of anycast services over the years. I think it's definitely true that managing a routing policy for your prefix (anycast or otherwise) through other people's networks takes care and vigilance; sometimes it takes money; it is rarely easy. I remember deploying root server nodes twenty years ago and finding that large, incumbent network operators who would only peer outside their territory caused a lot of increased latency and surprising paths. I remember European telcos who would prefer to route to other continents rather than peer within their capital cities to reach root servers, for entirely well-informed but ultimately non-technical reasons. Choosing heavy hammers like LOCAL_PREF for exit selection rather than leaving the door open to considering AS_PATH length is sometimes another example of non-technical cause and effect. It is not clear to me these kinds of thing are always (or even often) good examples of simple technical problems that can be solved with simple technical solutions. The idea that defining a well-known "anycast" community string attribute could make all of this better seems a little over-hopeful, shall we say. Joe