Testing a DNS Server


The first thing to consider is the client operating system from which the testing will be orchestrated. Windows generally does not make the top of the list in this regard. The use of a *unix* variant, Linux or (FreeBSD) is *very* highly recommended. These operating systems were designed from the ground up to be networked operating systems. As a result, a plethora of tools is readily available, even in minimal OS configurations, to perform network related tasks and test procedures. My personal favorite is FreeBSD, and in fact this document is being prepared on my FreeBSD 7.0 desktop.

The DIG utility is provided with BIND¹ (currently the DNS server that runs most of the internet)

However; most *nix type operating systems have it included in one of the standard binary directories, even if BIND is not installed. Get to know DIG, as it will be your best friend in the DNS world. The following list of commands should give the reader some idea about it's capabilities:







dig @92.243.9.117 mx fourcalorieservers.com ---- This command displays the mail exchange server info for the fourcalorieservers.com domain as presented by the DNS server. The "92.243.9.117" dotted decimal octet is the address of the DNS server being queried.


dig @92.243.9.117 ns fourcalorieservers.com ---- This command displays the name server info for the fourcalorieservers.com domain as presented by the DNS server. The "92.243.9.117" dotted decimal octet is the address of the DNS server being queried.


dig @92.243.9.117 fourcalorieservers.com ---- This command displays the DNS address record for the naked (or root) domain name (fourcalorieservers.com)


dig @92.243.9.117 -x 92.243.9.117 ---- This command displays the reverse (PTR) record for the address 209.40.199.130


dig @92.243.9.117 a fourcalorieservers.com ---- This command displays the dns "address" record for the naked domain name (and is the equivalent of the previously shown naked domain address query command. The "address" record is the default query type for DiG, when no explicit query type is given. This is also true of the older nslookup utility. The nslookup utility is available on Windows, and is used within a command shell (Start menu / run / command).


dig @92.243.9.117 a www.fourcalorieservers.com ---- This command displays the dns "address" record for the world wide web server at the fourcalorieservers.com domain. Note that there is nothing magical about the "www" domain name. It is the www server only if the domain operator intends it to be, and is usually assigned, by tradition/fiat to be the www server (In web guru parlance called the http server).


dig @92.243.9.117 a mail.fourcalorieservers.com ---- This command displays the dns "address" record for the mail server at the fourcalorieservers.com domain. Note that there is nothing magical about the "mail" domain name. It is the mail server only if the domain operator intends it to be, and is usually assigned, by tradition/fiat to be the mail server (In internet guru parlance called the smtp server. Note also that the mail server domain name is usually retrieved, as a first step, using the mx command).


Other nifty uses of the DiG tool:


dig +trace fourcalorieservers.com ---- this will force DiG to get the nameserver information directly from the root servers.

   hints2# dig +trace fourcalorieservers.com

   ;  DiG 9.4.2-P2  +trace fourcalorieservers.com
   ;; global options:  printcmd

   ;; Received 512 bytes from 192.33.4.12#53(c.root-servers.net) in 58 ms

   fourcalorieservers.com.	172800	IN	NS	ns101.fourcalorieservers.com.
   fourcalorieservers.com.	172800	IN	NS	ns701.fourcalorieservers.com.
   ;; Received 112 bytes from 192.52.178.30#53(K.GTLD-SERVERS.NET) in 167 ms

   fourcalorieservers.com.	14400	IN	A	92.243.9.117
   fourcalorieservers.com.	14400	IN	NS	ns701.fourcalorieservers.com.   i
   fourcalorieservers.com.	14400	IN	NS	ns101.fourcalorieservers.com.
   ;; Received 128 bytes from 92.243.9.117#53(ns701.fourcalorieservers.com) in 162 ms

      

dig -p 5350 @10.0.1.21 www.fourcalorieserves.com


The preceding command will use a special port instead of the default (53), useful for instances where the DNS servers are behind a firewall and/or router.

dig -4 www.fourcalorieservers.com ---- force the use of inet version 4 only. (note that in this case the address of the server was not supplied, so the default resolver address must be used). Using this switch may result in faster responses, because many resolvers in the *nix world send the ipv6 request first, multiple times, usually receiving a "bounce" as a result of the continued use of mainly ipv4 DNS servers.

DiG has many other query capabilities, but I have expressed command syntax for the ones that are most directly applicable to the little FourCalorieServers/DNS server. Read the Dig manual for more information.






** The nslookup Utility

Note that we mentioned nslookup. It is officially deprecated, and in the future may not be available. However; since it is one of the only tools natively available to users of Windows, some explanation is a good thing:


Start nslookup with a command shell in Windows, by typing nslookup. The nslookup prompt should appear. Then set the desired DNS server to use in subsequent query operations, by typing "Server 92.243.9.117" and pressing the enter key. Note that the given address is for fourcalorieservers.com, and hey, you may use it if you like. :-) Note that a domain name for the server may be used if your system configuration has a pointer to a public DNS server.

Type the domain name that you would like to resolve to an address. Type www.fourcalorieservers.com, for instance. A dotted decimal address should be shown.



¹ Bind (Berkley Internet Name Daemon) is maintained by the Internet Software Consortium (not affiliated with this site)


- Datazygte, Inc, contact: ronscheckelhoff@fourcalorieservers.com