On Fri, Jan 12, 2018 at 11:02:02AM +0100, Robert Kisteleki <robert@ripe.net> wrote a message of 31 lines which said:
I'd think it's relatively difficult to automatically (i.e. system) tag probes as "intentionally single stack", as we don't really know if that's a misconfiguration (e.g. DHCP server is down) or intentional.
Note there is some work at the IETF, in the sunset4 working group, to address this very problem. Document draft-ietf-sunset4-gapanalysis (the gap analysis) describe it as "3.1. Indicating that IPv4 connectivity is unavailable PROBLEM 1: When an IPv4 node boots and requests an IPv4 address (e.g., using DHCP), it typically interprets the absence of a response as a failure condition even when it is not." There is no standard solution today. Document draft-ietf-sunset4-noipv4 proposed "a new DHCPv6 option and a new Router Advertisement option to inform a dual-stack host or router that IPv4 can be turned off" but this document died, I don't know why.