From 00676cf152665e91122cad21c864bfc912d93550 Mon Sep 17 00:00:00 2001
From: Mattia Tadini <tadini@poloinformatico.it>
Date: Wed, 8 Jan 2025 16:58:50 +0000
Subject: [PATCH] Add dns-healtcheck

---
 dns-healtcheck | 71 ++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 71 insertions(+)
 create mode 100644 dns-healtcheck

diff --git a/dns-healtcheck b/dns-healtcheck
new file mode 100644
index 0000000..4d03313
--- /dev/null
+++ b/dns-healtcheck
@@ -0,0 +1,71 @@
+##
+##   Automatically DNS Healthcheck
+##   
+##
+##   script by Mattia Tadini
+##   created: 2025-01-05
+##   updated: 2025-01-05
+##   tested on: RouterOS 7.16.2 / multiple HW devices, won't work on 6.49 and older (different update process & value naming)
+##
+
+###### define variables here
+
+:local sysname [/system identity get name];
+:local Email "[YOUR EMAIL ADDRESS FOR NOTIFICATIONS HERE]"; ###### please configure SMTP in /tools/email to use mail notifications
+
+:local PrimaryDNS "[YOUR PRIMARY DNS IP HERE]";
+:local BackupDNS "1.1.1.1"; #### CloudFare public DNS as backup (better than Google's)
+:local TestDomain "google.com"
+
+:local ConfiguredDNS [/ip dns get servers];
+
+###### when router is in its primary configuration
+:if ($PrimaryDNS = $ConfiguredDNS) do={
+    :do { 
+        ###### test resolution
+        :put [:resolve $TestDomain server $ConfiguredDNS];
+
+        ###### generate syslog messages
+        /log info "Primary DNS $PrimaryDNS healthcheck completed, no issues";
+
+    } on-error={ 
+        :put "resolver failed"; 
+
+        ###### generate syslog messages
+        /log info "name resolution using primary DNS $PrimaryDNS failed";
+        /log info "temporary setting backup DNS $BackupDNS as primary";
+
+        ###### update DNS with backup DNS
+        /ip dns set servers=$BackupDNS; 
+
+        ###### send notification email
+        /tool e-mail send to="$Email" subject="$sysname script notification: Primary DNS $PrimaryDNS down" body="Primary DNS $PrimaryDNS is down.\r\nDNS configuration changed to backup DNS $BackupDNS."
+        /log info "notification email to $Email sent";
+    }
+}
+
+###### when router is in its backup configuration
+:if ($BackupDNS = $ConfiguredDNS) do={
+    :do { 
+        ###### test resolution
+        :put [:resolve $TestDomain server $PrimaryDNS];
+
+        ###### generate syslog messages
+        /log info "name resolution using primary DNS $PrimaryDNS working now";
+        /log info "restoring original DNS configuration";
+
+        ###### revert back DNS configuration to original
+        /ip dns set servers=$PrimaryDNS;
+
+        ###### send notification email
+        /tool e-mail send to="$Email" subject="$sysname script notification: Primary DNS $PrimaryDNS up" body="Primary DNS $PrimaryDNS is up.\r\nOriginal DNS configuration restored."
+        /log info "notification email to $Email sent";
+        
+    } on-error={ 
+        :put "resolver failed";
+
+        ###### generate syslog messages
+        /log info "system is configured with backup DNS $BackupDNS";
+        /log info "Primary DNS $PrimaryDNS is still down, next check in 10 seconds";
+    }
+}
\ No newline at end of file