diff --git a/neutron/plugins/ml2/drivers/ovn/mech_driver/ovsdb/ovn_db_sync.py b/neutron/plugins/ml2/drivers/ovn/mech_driver/ovsdb/ovn_db_sync.py
index bf3721495b5..1b50088df7c 100644
--- a/neutron/plugins/ml2/drivers/ovn/mech_driver/ovsdb/ovn_db_sync.py
+++ b/neutron/plugins/ml2/drivers/ovn/mech_driver/ovsdb/ovn_db_sync.py
@@ -863,10 +863,20 @@ def _sync_subnet_dhcp_options(self, ctx, db_networks,
             LOG.warning('DHCP options for subnet %s is present in '
                         'Neutron but out of sync for OVN', subnet_id)
             if self.mode == SYNC_MODE_REPAIR:
+                # If neutron-server is running we could race and find a
+                # subnet without a cached network, just skip it to avoid
+                # a KeyError below.
+                network_id = utils.ovn_name(subnet['network_id'])
+                if network_id not in db_networks:
+                    LOG.warning('Network %s for subnet %s not found in OVN NB '
+                                'DB network cache, possible race condition, '
+                                'please check that neutron-server is stopped! '
+                                'Skipping subnet.', network_id, subnet_id)
+                    continue
                 try:
-                    LOG.debug('Adding/Updating DHCP options for subnet %s in '
-                              ' OVN NB DB', subnet_id)
-                    network = db_networks[utils.ovn_name(subnet['network_id'])]
+                    LOG.warning('Adding/Updating DHCP options for subnet %s '
+                                'in OVN NB DB', subnet_id)
+                    network = db_networks[network_id]
                     # _ovn_client._add_subnet_dhcp_options doesn't create
                     # a new row in DHCP_Options if the row already exists.
                     # See commands.AddDHCPOptionsCommand.
diff --git a/neutron/tests/unit/plugins/ml2/drivers/ovn/mech_driver/ovsdb/test_ovn_db_sync.py b/neutron/tests/unit/plugins/ml2/drivers/ovn/mech_driver/ovsdb/test_ovn_db_sync.py
index 0c81c6a0576..f73eada8290 100644
--- a/neutron/tests/unit/plugins/ml2/drivers/ovn/mech_driver/ovsdb/test_ovn_db_sync.py
+++ b/neutron/tests/unit/plugins/ml2/drivers/ovn/mech_driver/ovsdb/test_ovn_db_sync.py
@@ -104,6 +104,17 @@ def setUp(self):
                          'gateway_ip': '20.0.0.1',
                          'dns_nameservers': [],
                          'host_routes': [],
+                         'ip_version': 4},
+                        # A subnet without a known network should be skipped,
+                        # see bug #2045811
+                        {'id': 'notfound',
+                         'network_id': 'notfound',
+                         'enable_dhcp': True,
+                         'cidr': '30.0.0.0/24',
+                         'tenant_id': 'tenant1',
+                         'gateway_ip': '30.0.0.1',
+                         'dns_nameservers': [],
+                         'host_routes': [],
                          'ip_version': 4}]
 
         self.security_groups = [
diff --git a/neutron/tests/unit/plugins/ml2/drivers/ovn/mech_driver/test_mech_driver.py b/neutron/tests/unit/plugins/ml2/drivers/ovn/mech_driver/test_mech_driver.py
index e1c39a5ea61..b0c77ecd4d2 100644
--- a/neutron/tests/unit/plugins/ml2/drivers/ovn/mech_driver/test_mech_driver.py
+++ b/neutron/tests/unit/plugins/ml2/drivers/ovn/mech_driver/test_mech_driver.py
@@ -1515,9 +1515,10 @@ def test_enable_subnet_dhcp_options_in_ovn_ipv4(self, grm, gps):
         self.mech_driver.nb_ovn.set_lswitch_port.assert_has_calls(
             set_lsp_calls, any_order=True)
 
+    @mock.patch.object(ovn_utils, 'get_system_dns_resolvers')
     @mock.patch.object(db_base_plugin_v2.NeutronDbPluginV2, 'get_ports')
     @mock.patch.object(n_net, 'get_random_mac')
-    def test_enable_subnet_dhcp_options_in_ovn_ipv6(self, grm, gps):
+    def test_enable_subnet_dhcp_options_in_ovn_ipv6(self, grm, gps, gsd):
         grm.return_value = '01:02:03:04:05:06'
         gps.return_value = [
             {'id': 'port-id-1', 'device_owner': 'nova:compute'},
@@ -1530,6 +1531,7 @@ def test_enable_subnet_dhcp_options_in_ovn_ipv6(self, grm, gps):
                  {'opt_value': '10::34', 'ip_version': 6,
                    'opt_name': 'dns-server'}]},
             {'id': 'port-id-10', 'device_owner': 'network:foo'}]
+        gsd.return_value = []
         subnet = {'id': 'subnet-id', 'ip_version': 6, 'cidr': '10::0/64',
                   'gateway_ip': '10::1', 'enable_dhcp': True,
                   'ipv6_address_mode': 'dhcpv6-stateless',
@@ -1696,7 +1698,9 @@ def test_update_subnet_dhcp_options_in_ovn_ipv6(self):
         self.mech_driver.nb_ovn.add_dhcp_options.assert_called_once_with(
             subnet['id'], **new_options)
 
-    def test_update_subnet_dhcp_options_in_ovn_ipv6_not_change(self):
+    @mock.patch.object(ovn_utils, 'get_system_dns_resolvers')
+    def test_update_subnet_dhcp_options_in_ovn_ipv6_not_change(self, gsd):
+        gsd.return_value = []
         subnet = {'id': 'subnet-id', 'ip_version': 6, 'cidr': '10::0/64',
                   'gateway_ip': '10::1', 'enable_dhcp': True,
                   'ipv6_address_mode': 'dhcpv6-stateless',