We have already discussed Nagios nrpe configuration and you may get an error when you check dns in client system,

# /usr/local/nagios/libexec/check_dns -H thelinuxfaq.com

-bash: /usr/local/nagios/libexec/check_dns: /lib/ld-linux.so.2: bad ELF interpreter: No such file or directory
# yum install glibc.i686

# /usr/local/nagios/libexec/check_dns -H thelinuxfaq.com

DNS CRITICAL - '/usr/bin/nslookup -sil' msg parsing exited with no address

check it now the lslookup is
# ls -al '/usr/bin/nslookup'

-rwxr-xr-x 1 root root 119864 Jan  20  2014 /usr/bin/nslookup
#  yum install bind-utils

# /usr/local/nagios/libexec/check_dns -H domainname.com

DNS OK: 0.027 seconds response time. domainname.com returns|time=0.026621s;;;0.000000

If you are using Ubuntu operating system,
#  apt-get update

#  apt-get install ia32-libs