diff --git a/config-dist.php b/config-dist.php
index fb45533b60c..90989bbd28a 100644
--- a/config-dist.php
+++ b/config-dist.php
@@ -742,6 +742,9 @@ $CFG->admin = 'admin';
 // Force developer level debug and add debug info to the output of cron
 // $CFG->showcrondebugging = true;
 //
+// Force result of checks used to determine whether a site is considered "public" or not (such as for site registration).
+// $CFG->site_is_public = false;
+//
 //=========================================================================
 // 8. FORCED SETTINGS
 //=========================================================================
diff --git a/lib/classes/ip_utils.php b/lib/classes/ip_utils.php
index d2e9a3dd02e..387df8f9211 100644
--- a/lib/classes/ip_utils.php
+++ b/lib/classes/ip_utils.php
@@ -245,4 +245,22 @@ final class ip_utils {
         return false;
     }
 
+    /**
+     * Return IP address for given hostname, or null on failure
+     *
+     * @param string $hostname
+     * @return string|null
+     */
+    public static function get_ip_address(string $hostname): ?string {
+        if (self::is_domain_name($hostname)) {
+            $address = gethostbyname($hostname);
+
+            // If address is different from hostname, we have success.
+            if (strcasecmp($address, $hostname) !== 0) {
+                return $address;
+            }
+        }
+
+        return null;
+    }
 }
diff --git a/lib/moodlelib.php b/lib/moodlelib.php
index 542fd0d32d6..75c6175f4ae 100644
--- a/lib/moodlelib.php
+++ b/lib/moodlelib.php
@@ -10571,18 +10571,26 @@ function get_callable_name($callable) {
  * It just performs some simple checks, and mainly is used for places where we want to hide some options
  * such as site registration when $CFG->wwwroot is not publicly accessible.
  * Good thing is there is no false negative.
+ * Note that it's possible to force the result of this check by specifying $CFG->site_is_public in config.php
  *
  * @return bool
  */
 function site_is_public() {
     global $CFG;
 
+    // Return early if site admin has forced this setting.
+    if (isset($CFG->site_is_public)) {
+        return (bool)$CFG->site_is_public;
+    }
+
     $host = parse_url($CFG->wwwroot, PHP_URL_HOST);
 
     if ($host === 'localhost' || preg_match('|^127\.\d+\.\d+\.\d+$|', $host)) {
         $ispublic = false;
     } else if (\core\ip_utils::is_ip_address($host) && !ip_is_public($host)) {
         $ispublic = false;
+    } else if (($address = \core\ip_utils::get_ip_address($host)) && !ip_is_public($address)) {
+        $ispublic = false;
     } else {
         $ispublic = true;
     }