diff --git a/systemvm/patches/debian/config/opt/cloud/bin/cs/CsGuestNetwork.py b/systemvm/patches/debian/config/opt/cloud/bin/cs/CsGuestNetwork.py
index e1afb92c8ea..d23a870af69 100755
--- a/systemvm/patches/debian/config/opt/cloud/bin/cs/CsGuestNetwork.py
+++ b/systemvm/patches/debian/config/opt/cloud/bin/cs/CsGuestNetwork.py
@@ -38,13 +38,15 @@ class CsGuestNetwork:
     def get_dns(self):
         if not self.guest:
             return self.config.get_dns()
-        # Can a router provide dhcp but not dns?
-        if 'dns' in self.data and 'router_guest_gateway' in self.data:
-            return [self.data['router_guest_gateway']] + self.data['dns'].split(',')
-        elif "router_guest_gateway" in self.data:
-            return [self.data['router_guest_gateway']]
-        else:
-            return [""]
+
+        dns = []
+        if not self.config.use_extdns() and 'router_guest_gateway' in self.data:
+            dns.append(self.data['router_guest_gateway'])
+
+        if 'dns' in self.data:
+            dns.extend(self.data['dns'].split(','))
+
+        return dns or ['']
 
     def set_dns(self, val):
         self.data['dns'] = val