check_dig is case sensitive about the query answer which leads to a warning: Server not found in ANSWER SECTION.
See verbose output: /usr/lib/nagios/plugins/check_dig -H dns-cache2.switch.ch -vvvv -l 6to4-relay.switch.ch /usr/bin/dig @dns-cache2.switch.ch -p 53 6to4-relay.switch.ch -t A Looking for: '6to4-relay.switch.ch' ;; ANSWER SECTION: 6TO4-RELAY.switch.ch. 81981 IN A 130.59.31.253 ;; AUTHORITY SECTION: switch.ch. 2221 IN NS ns2.switch.ch. switch.ch. 2221 IN NS scsnms.switch.ch. ;; ADDITIONAL SECTION: ns2.switch.ch. 160647 IN A 130.59.138.49 ns2.switch.ch. 160647 IN AAAA 2001:620:0:1b:5054:ff:fe74:8780 scsnms.switch.ch. 160647 IN A 130.59.1.30 scsnms.switch.ch. 160647 IN A 130.59.10.30 scsnms.switch.ch. 160647 IN AAAA 2001:620::1 ;; Query time: 12 msec ;; SERVER: 2001:620:0:ff::3#53(2001:620:0:ff::3) ;; WHEN: Fri Feb 7 12:42:51 2014 ;; MSG SIZE rcvd: 208 DNS WARNING - 0.033 seconds response time (Server not found in ANSWER SECTION)|time=0.033127s;;;0.000000 -- Reply to this email on GitHub: https://github.com/monitoring-plugins/monitoring-plugins/issues/1233
