Using IP to get DNS FQDN Hostname

[tmroberts]

I'm fairly new to zabbix so this is probably a lot easier than I am thinking. We currently have our Zabbix environment set up to send the IP and not use DNS. In the in environment that I work in we are using VLAN's that take the internal IP and NAT them to an external IP. Is there any way in the templates to write a macro or something to take the IP it receives and lookup the FQDN of the hostname?

Example: the following are clones of each other and use different VLAN's. The internal static IP (i.e. 172.16.10.xxx) is the same but the external IP has a different subnet for each (i.e 10.220.yy.xxx).
test.domain1.com
test.domain2.com

Is there a way, maybe with HOST.DNS, to take the IP and do a DNS lookup for the hostname FQDN? If so, how? I've found the macro documentation, but i'm not understanding how to work that into the template.

[nobodysu]

You can create an external check:

http://i.imgur.com/yQRjGEg.png

This script will print a dns name of an ip:

/usr/bin/host "$1"

And then you can trigger if host's PTR is not 'example.org':

{Template:dnscheck.sh[{HOST.IP}].regexp(pointer example.org.$)}=0