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I found explanations by Cloudflare and DNS Made Easy quite vague on the implementation of these records - it was something about IP address caching.

Do those records only retrieve A and AAAA records of a target domain name?

Could you explain in detail how it works during the DNS query and where those IP's are fetched from?

t7e
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1 Answers1

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For now, there is nothing standard here. So each DNS provider is free to implement things the way it wants.

But broadly:

  • a CNAME is an alias between two names, for all record types; so in theory all record types should be resolved; however this kind of setup is mostly used for webhosting, so A+AAAA record types might be enough (should be documented by the provider)
  • there is work underway to finally define a new record type to do that; however this is not the first attempt (we already have DNAME, BNAME, etc.) so it might succeed or not, and then providers may implement it or not
  • typically there is two cases once you add such kind of record in your zone:
    • either the final resolution is done at this time, when the zone is provisioned, hence the real final records are directly put into the zone (simplest model, but then you have the problem of refreshing those records as the destination can change at any time)
    • or the final resolution is done by the authoritative nameserver of the zone, when the query comes (more complicated at the architecture level because mixing authoritative and recursive nameserver comes with its danger, there is a performance problem as the nameserver have more things to do and right when the query is to be replied to, but the records are always fresh because queried right at the moment they are needed - however their TTL should be honoured).
Patrick Mevzek
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