Flags used by dig output

And in case you've noticed, every time we perform a lookup of a domain through dig, there's some extra information in the header of the output (right before the actual answer of our query is displayed).

The flags are useful here. But what do those flags in DNS terms mean?

• AA: Authorative Answer: the nameserver that answered the query is the authorative (responsible) nameserver for that domain. Record shown in this query are those that will be known throughout the world.
  
• RD: Recursion Desired (see example below).
  
• RA: Recursion Available.
  
• QR: Query Response: the answer we received seems pretty reasonable, and could be real.
  

Query the root nameservers

And to show the "recursion" meaning, in DNS terms, here's the nameserver query for the domain "hosangit.com", when asked to one of the Root Servers.

Loads of information there ... First of, the "authority section" tells us the root nameservers for the .BE top level domain. These nameservers should be queried for the correct nameserver lookup. The flag "rd" means "recursion desired", and tells us we should consult one of the authoritative nameservers given -- because the root nameserver cannot tell us the answer.

I think I'll leave it at that ... there's lots more to cover about dig, and DNS in general, but I guess if you made it this far through the explanation -- you should at least deserve a tap on the shoulder. Congratulations!

DNS Requests contain questions that specify a name (or maybe a somewhat arbitrary text field) and a record type - the content of the response will vary depending on the type. Most requests are simple direct lookups of a server name looking for an ip-address in response (Type A) but some will be looking for more information on name servers themselves (Type NS), mail records (Type MX) and other services (Type SRV that will return names, ports, weights and priorities). DNS responses contain answers to these questions, possibly more than one if the request requires that and are not always just ip-addresses.