adds config option for external nameserver

ddns.sh

@@ -1,5 +1,12 @@
 #!/bin/bash
 
+# The DNS-server IP to use for checking the domain->IP mapping
+# If the local system has it's own DNS server which maps IPs differently
+# this should point to an external DNS like 1.1.1.1
+NAMESERVER="1.1.1.1"
+
+# ----- END CONFIG -------------------------------
+
 SCRIPTPATH="$( cd "$(dirname "$0")" >/dev/null 2>&1 ; pwd -P )"
 
 DOMAIN="$1"
@@ -20,7 +27,7 @@ if [[ "${PROBE_DOMAIN}" == \*.* ]]; then
     PROBE_DOMAIN="probe.${PROBE_DOMAIN:2}"
     echo "Probe domain is ----------> ${PROBE_DOMAIN}"
 fi
-DNS_IP=$(dig +short ${PROBE_DOMAIN})
+DNS_IP=$(dig @${NAMESERVER} +short ${PROBE_DOMAIN})
 echo "Current DNS-IP -----------> ${DNS_IP}"