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I'm looking over a file in a zone file:

@ IN SOA (
; Note: Increase serial number as part of modifying this file.
2000000014 ; Serialnumber
3600 ; Refresh
7200 ; Retry
604800 ; Expire
3600 ) ; Minimum, Use a much smaler value durin
g setup
@ IN MX 10
@ IN MX 20
@ IN MX 30 IN SRV 0 0 443

Now, when I try to resolve (using type=srv), it resolved to

This makes me question if should actually be (notice the extra ".")

I tried to look in the bind named manual, but could'nt figure out why some domains have the extra ".". Is this to mark it as a FQDN?

Unfortunally, I cannot test this at my current location.

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up vote 3 down vote accepted

Yes, the final . marks the name as a FQDN. If it was not present, the value of .$ORIGIN would be automatically appended.

  • For example, the entries

    $ORIGIN IN SRV 0 0 443

    are equivalent to

    _autodiscover._tcp IN SRV 0 0 443 w3

You're also right that in the zone file you posted, the SRV record is missing the final . in its name – resulting in in the actual zone. (Alternatively, you can remove the domain entirely for an easier-to-read zonefile – see example #2 above.)

The zone file format used by bind is described in RFC 1035 section 5.1:

[...] Domain names that end in a dot are called absolute, and are taken as complete. Domain names which do not end in a dot are called relative; the actual domain name is the concatenation of the relative part with an origin specified in a $ORIGIN, $INCLUDE, or as an argument to the master file loading routine.

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