Generic anycast addresses...

[Ted Lemon <[e-mail]>]

I was looking through the IANA registry for anycast addresses with an idea of what I wanted, and was surprised to learn that no such thing exists.   I’m curious if what I want is something that’s already been shot down in flames, or something for which no energy has existed to do.

Right now it appears that anycast addresses either aren’t special (that is, they are just IP addresses in someone’s prefix) or are link-specific (e.g., the subnet router anycast address, which if I understand it correctly is constructed of <local-prefix>::0).

What I am looking for is an anycast address that won’t match any local prefix, so that it filters out towards an egress router and is caught somewhere along the way, or worst case, at the egress.   I can see where this would have gone down in flames, since we don’t want anycast packets to keep going toward the backbone and create congestion, so that might explain why this hasn’t happened.   But we do have the notion of scopes, e.g. for multicast, and that would seem to apply for anycast as well.   We do allow multicast in scopes larger than the local subnet, and AFAIK this has not melted the Internet.

The actual use case I have for this is wanting to be able to have a constrained device send a unicast discovery or announcement which can be assumed to be caught and handled by infrastructure.

So, is this something that’s been talked about and abandoned as a terrible idea, or abandoned because nobody wanted to do the process to make it happen, or is it (seems unlikely) an innovation on my part?   Or is it already done and I just managed to not find the document describing it?

Thanks!