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I've noticed that AWS's DNS service (Route53) appends a dot (.) at the end of every DNS URL:

ns-xxx.awsdns-yy.co.uk.
ns-xxx.awsdns-yy.net.
ns-xxx.awsdns-yy.org.
ns-xxx.awsdns-yy.com.

Question: Is this a bug, or should I include the . in my DNS settings?

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43

The dot at the end is correct.

It's a little-known fact, but fully-qualified (unambiguous) DNS domain names have a dot at the end. People running DNS servers usually know this (if you miss the trailing dots out, your DNS configuration is unlikely to work) but the general public usually doesn't. A domain name that doesn't have a dot at the end is not fully-qualified and is potentially ambiguous. This was documented in the DNS specification, RFC 1034, way back in 1987:

Since a complete domain name ends with the root label, this leads to a
printed form which ends in a dot.  We use this property to distinguish between:

   - a character string which represents a complete domain name
     (often called "absolute").  For example, "poneria.ISI.EDU."

   - a character string that represents the starting labels of a
     domain name which is incomplete, and should be completed by
     local software using knowledge of the local domain (often
     called "relative").  For example, "poneria" used in the
     ISI.EDU domain.

From here

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    Note that Go Daddy seems to have overlooked this fact on there interface where a user can specify authoritative nameservers on domains registered with them, given the number of upvotes on my answer to Entering Route53 Nameservers Gives Me Errors on Godaddy on Stack Overflow, where the answer is "remove the trailing dot" -- even though you are right -- this is the technically correct form. (+1)
    – Michael - sqlbot
    Sep 14, 2016 at 21:14
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    up until today godaddy doesn't recognize trailing period at the end of NS is a valid charachter and will not accept the change through UI. It is really absurd such domain hosting like godaddy is not up to date with best practices.
    – TechNerd
    May 17, 2019 at 10:20

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