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i.e. is there a pingable address in each, as has been discussed here just a few times?

ping is ok, but routing table entry existence seems better. ping can fail for lots of reasons and what we're really testing is routing, not icmp end-to-end, right?

There's a difference between reachability and routability. The lack of a routing table entry indicates a different problem which implicates routing and reachability problems. I don't agree that reachability is implied with routability.

if it's useful, i'd be happy to report what percentage of my peers have/don't have routes to these prefixes.

I'd be interested. Best, -M<