[GTALUG] Reverse DNS different that DNS server (reverse is a local address)

[D. Hugh Redelmeier]

I have no time for a careful answer.  But it is important that you 
understand these points:

- DNS is a distributed tree, with nodes that are authoritative for 
  particular domains.

- there is caching (recursive servers) if you trust them (almost always 
  one does).  Unless you are using DNSSec, the caching server can lie, 
  sometimes usefully.

- the forward domain is technically unrelated to the reverse domain.

  The forward domain lookup uses a conventional domain name as the
  key.

  The reverse lookup uses the IP address (in a funny format) as the
  key.

- Reverse example: to lookup the reverse for IPv4 address 1.2.3.4,
  your system actually queries 4.3.2.1.in-addr.arpa.  I think you can
  see how that is constructed.

- the reverse domain is a mystery to most people (because it mostly 
  doesn't matter to most users).  If you run a mail server, it does 
  matter.

- whoever provided you with your IP address controls the reverse
  domain for that IP address.  Generally, if you pay for a static IP
  address, they will let you specify what you want them to put in the
  reverse domain for that IP address.  Most ordinary consumers don't
  have static addresses and are not given a say in what the reverse
  says.

- if your provider provides you with a CIDR of network addresses,
  static, they may delegate the reverse domain for that CIDR to a DNS
  of your choosing.  This is not the normal home case.