move the dns_external check to using a group variable in the nagios group. This takes it out of the main inventory where its names do not match and this other group was not used in any other playbook

inventory/group_vars/nagios

@@ -105,6 +105,13 @@ iad2_external:
   - retrace01.fedoraproject.org
   - secondary01.fedoraproject.org
 
+dns_external:
+  - ns-iad01.fedoraproject.org
+  - ns-iad02.fedoraproject.org
+  - ns02.fedoraproject.org
+  - ns05.fedoraproject.org
+
+
 # When you have a group which comes up with empty members in all.cfg, it
 # is because it contains all hosts which aren't pinganble. You may want
 # to add that group to this list. Other items on this list are ones

inventory/inventory

@@ -392,12 +392,6 @@ ns02.fedoraproject.org
 ns05.fedoraproject.org
 ns13.rdu2.fedoraproject.org
 
-[dns_external]
-ns-iad01.iad2.fedoraproject.org
-ns-iad02.iad2.fedoraproject.org
-ns02.fedoraproject.org
-ns05.fedoraproject.org
-
 [odcs_frontend]
 odcs-frontend01.iad2.fedoraproject.org
 

roles/nagios_server/templates/nagios/hostgroups/all-external.cfg.j2

@@ -1,7 +1,7 @@
 define hostgroup {
         hostgroup_name  dns
         alias           DNS Servers
-        members         {% for host in groups["dns_external"]|sort %} {{ hostvars[host]["inventory_hostname_short"] }}.fedoraproject.org {% if not loop.last %}, {% endif %} {% endfor %}
+        members         {% for host in vars['dns_external']|sort %}{{ host }}{% if not loop.last %}, {% endif %} {% endfor %}
 
 }