Entry

How can I send a recursive query to a specific server?

Nov 20th, 2003 03:59
Jonathan de Boyne Pollard, Brian Coogan, Rob Mayoff,

This is useful when testing DNS servers.
Unlike dnsq, the dnsqr command does not accept the DNS server 
address as a command-line argument.  It normally finds the DNS 
server address in /etc/resolv.conf.
However, you can easily override /etc/resolv.conf by putting an 
IP address in the environment variable DNSCACHEIP.  In 
Bourne-type shells (sh, ash, bash, ksh, zsh), you can just do 
this:
  DNSCACHEIP=1.2.3.4 dnsqr a example.com
That will send a recursive query for example.com's A records to 
1.2.3.4.
In csh-type shells (works for all shell types), you can do 
this:
  env DNSCACHEIP=1.2.3.4 dnsqr a example.com
Whatever shell you use, you can also create a shell script 
called "dnsr" that acts just like dnsq:
  #!/bin/sh
  DNSCACHEIP=`dnsip "$3"`
  if [ "$DNSCACHEIP" = "" ]; then
      DNSCACHEIP=0.0.0.0
  fi
  export DNSCACHEIP
  exec dnsqr "$1" "$2"
Because it uses the output from "dnsip" directly as the value 
for the environment variable, the same caveat, about providing 
as the third argument domain names that map to more than one IP 
address, that applies to the "dnsqrx" script at
http://homepages.tesco.net./~J.deBoynePollard/Softwares/djbdns.
html#dnsqrx
also applies to this script.