diff --git a/knotctl/__init__.py b/knotctl/__init__.py
index a768fd2..4a9e1e7 100755
--- a/knotctl/__init__.py
+++ b/knotctl/__init__.py
@@ -232,7 +232,8 @@ def run_list(url: str,
 
 
 def run_openstack_sync(cloud: str, name: str, zone: str, headers: dict,
-                       baseurl: str, jsonout: bool):
+                       baseurl: str, jsonout: bool, ipv4: bool, ipv6: bool):
+    # List DNS records for name
     url = setup_url(
         baseurl,
         None,  # arguments,
@@ -242,103 +243,72 @@ def run_openstack_sync(cloud: str, name: str, zone: str, headers: dict,
         None,  # ttl,
         zone,
     )
-    current_records = run_list(url, jsonout=True, headers=headers, ret=True)
+    response = run_list(url, jsonout=True, headers=headers, ret=True)
+    if isinstance(response, dict):
+        if response["Code"] == 404:
+            response = []
+        else:
+            output(error(f'{name}: could not list records', 'API Error'))
+            sys.exit(1)
+
+    # List of DNS records for name
+    dns_records = []
+    for record in response:
+        rtype = record['rtype']
+        rname = record['name'].rstrip('.')
+        raddr = record['data']
+        if rtype not in ('A', 'AAAA'):
+            continue
+        if f'{name}.{zone}' != rname:
+            output(error(f'{rname}: not the DNS name asked for', 'API Error'))
+            sys.exit(1)
+        dns_records.append((rname, rtype, raddr))
+
+    # List instance addresses in openstack
     openstack_addresses = get_openstack_addresses(cloud, name)
-    if current_records["Code"] == 404:
-        for address in openstack_addresses:
-            rtype = None
-            if address["version"] == 4:
-                rtype = "A"
-            elif address["version"] == 6:
-                rtype = "AAAA"
-            if rtype:
-                url = setup_url(
-                    baseurl,
-                    None,  # arguments,
-                    address["addr"],  # data,
-                    name,
-                    rtype,
-                    None,  # ttl,
-                    zone,
-                )
-                run_add(url, jsonout, headers)
-    else:
-        previpv4 = False
-        previpv6 = False
-        curripv4 = False
-        curripv6 = False
-        for record in current_records:
-            if record.type == "A":
-                previpv4 = record.data
-            elif record.type == "AAAA":
-                previpv6 = record.data
-            for address in openstack_addresses:
-                rtype = None
-                if address.version == 4:
-                    rtype = "A"
-                    curripv4 = True
-                elif address.version == 6:
-                    rtype = "AAAA"
-                    curripv6 = True
-                if rtype and recor.type == rtype:
-                    if record.data == address.addr:
-                        continue
-                    else:
-                        url = setup_url(
-                            baseurl,
-                            None,  # arguments,
-                            address.addr,  # data,
-                            name,
-                            record.type,
-                            None,  # ttl,
-                            zone,
-                        )
-                        run_update(url, jsonout, headers)
-        if previpv4 and not curripv4:
+
+    # Add missing DNS records
+    for address in openstack_addresses:
+        rtype = None
+        if address["version"] == 4 and ipv4:
+            rtype = "A"
+        elif address["version"] == 6 and ipv6:
+            rtype = "AAAA"
+        if not rtype:
+            continue
+
+        raddr = address['addr']
+
+        wanted_record = (f'{name}.{zone}', rtype, raddr)
+
+        if wanted_record in dns_records:
+            dns_records.remove(wanted_record)
+        else:
             url = setup_url(
                 baseurl,
                 None,  # arguments,
-                previpv4,  # data,
+                raddr,  # data,
                 name,
-                "A",
-                None,  # ttl,
-                zone,
-            )
-            run_delete(url, jsonout, headers)
-        if previpv6 and not curripv6:
-            url = setup_url(
-                baseurl,
-                None,  # arguments,
-                previpv6,  # data,
-                name,
-                "AAAA",
-                None,  # ttl,
-                zone,
-            )
-            run_delete(url, jsonout, headers)
-        if curripv4 and not previpv4:
-            url = setup_url(
-                baseurl,
-                None,  # arguments,
-                curripv4,  # data,
-                name,
-                "A",
-                None,  # ttl,
-                zone,
-            )
-            run_add(url, jsonout, headers)
-        if curripv6 and not previpv6:
-            url = setup_url(
-                baseurl,
-                None,  # arguments,
-                curripv6,  # data,
-                name,
-                "AAAA",
+                rtype,  # rtype,
                 None,  # ttl,
                 zone,
             )
             run_add(url, jsonout, headers)
 
+    # Remove obsolete DNS records
+    for record in dns_records:
+        rname, rtype, raddr = record
+
+        url = setup_url(
+            baseurl,
+            None,  # arguments,
+            raddr,  # data,
+            name,
+            rtype,  # rtype,
+            None,  # ttl,
+            zone,
+        )
+        run_delete(url, jsonout, headers)
 
 def run_update(url: str, jsonout: bool, headers: dict):
     response = requests.patch(url, headers=headers)
@@ -557,6 +527,8 @@ def get_parser() -> dict:
     openstackcmd.add_argument("-n", "--name", required=True)
     openstackcmd.add_argument("-c", "--cloud", required=True)
     openstackcmd.add_argument("-z", "--zone", required=True)
+    openstackcmd.add_argument("--no-ipv4", action='store_true')
+    openstackcmd.add_argument("--no-ipv6", action='store_true')
 
     user_description = "View user information."
     usercmd = subparsers.add_parser("user", description=user_description)
@@ -645,7 +617,8 @@ def run(url, args, headers, baseurl, parser, username):
             run_zone(url, args.json, headers)
         elif args.command == "openstack-sync":
             run_openstack_sync(args.cloud, args.name, args.zone, headers,
-                               baseurl, args.json)
+                               baseurl, args.json,
+                               args.no_ipv4 is False, args.no_ipv6 is False)
         else:
             parser.print_help(sys.stderr)
             return 2