diff --git a/neutron/agent/linux/openvswitch_firewall/firewall.py b/neutron/agent/linux/openvswitch_firewall/firewall.py
index daf119735c3..d5cd184a63e 100644
--- a/neutron/agent/linux/openvswitch_firewall/firewall.py
+++ b/neutron/agent/linux/openvswitch_firewall/firewall.py
@@ -40,6 +40,7 @@ from neutron.agent.linux.openvswitch_firewall import constants as ovsfw_consts
 from neutron.agent.linux.openvswitch_firewall import exceptions
 from neutron.agent.linux.openvswitch_firewall import iptables
 from neutron.agent.linux.openvswitch_firewall import rules
+from neutron.common import utils as n_utils
 
 LOG = logging.getLogger(__name__)
 CONJ_ID_REGEX = re.compile(r"conj_id=(\d+),")
@@ -543,7 +544,8 @@ class OVSFirewallDriver(firewall.FirewallDriver):
                                    applied
 
         """
-        self.permitted_ethertypes = cfg.CONF.SECURITYGROUP.permitted_ethertypes
+        self.permitted_ethertypes = n_utils.parse_permitted_ethertypes(
+            cfg.CONF.SECURITYGROUP.permitted_ethertypes)
         self.int_br = self.initialize_bridge(integration_bridge)
         self._initialize_sg()
         self._update_cookie = None
@@ -1178,24 +1180,14 @@ class OVSFirewallDriver(firewall.FirewallDriver):
 
         # Allow custom ethertypes
         for permitted_ethertype in self.permitted_ethertypes:
-            if permitted_ethertype[:2] == '0x':
-                try:
-                    hex_ethertype = hex(int(permitted_ethertype, base=16))
-                    action = ('resubmit(,%d)' %
-                              ovs_consts.ACCEPTED_EGRESS_TRAFFIC_NORMAL_TABLE)
-                    self._add_flow(
-                        table=ovs_consts.BASE_EGRESS_TABLE,
-                        priority=95,
-                        dl_type=hex_ethertype,
-                        reg_port=port.ofport,
-                        actions=action
-                    )
-                    continue
-                except ValueError:
-                    pass
-            LOG.warning("Custom ethertype %(permitted_ethertype)s is not "
-                        "a hexadecimal number.",
-                        {'permitted_ethertype': permitted_ethertype})
+            action = ('resubmit(,%d)' %
+                      ovs_consts.ACCEPTED_EGRESS_TRAFFIC_NORMAL_TABLE)
+            self._add_flow(
+                table=ovs_consts.BASE_EGRESS_TABLE,
+                priority=95,
+                dl_type=permitted_ethertype,
+                reg_port=port.ofport,
+                actions=action)
 
         # Drop all remaining egress connections
         self._add_flow(
@@ -1390,22 +1382,12 @@ class OVSFirewallDriver(firewall.FirewallDriver):
 
         # Allow custom ethertypes
         for permitted_ethertype in self.permitted_ethertypes:
-            if permitted_ethertype[:2] == '0x':
-                try:
-                    hex_ethertype = hex(int(permitted_ethertype, base=16))
-                    self._add_flow(
-                        table=ovs_consts.BASE_INGRESS_TABLE,
-                        priority=100,
-                        dl_type=hex_ethertype,
-                        reg_port=port.ofport,
-                        actions='output:{:d}'.format(port.ofport)
-                    )
-                    continue
-                except ValueError:
-                    pass
-            LOG.warning('Custom ethertype %(permitted_ethertype)s is not '
-                        'a hexadecimal number.',
-                        {'permitted_ethertype': permitted_ethertype})
+            self._add_flow(
+                table=ovs_consts.BASE_INGRESS_TABLE,
+                priority=100,
+                dl_type=permitted_ethertype,
+                reg_port=port.ofport,
+                actions='output:{:d}'.format(port.ofport))
 
         self._initialize_ingress_ipv6_icmp(port)
 
diff --git a/neutron/common/utils.py b/neutron/common/utils.py
index 1b2b4dd19f4..4c240584f11 100644
--- a/neutron/common/utils.py
+++ b/neutron/common/utils.py
@@ -1088,3 +1088,23 @@ def sign_instance_id(conf, instance_id):
     secret = encodeutils.to_utf8(secret)
     instance_id = encodeutils.to_utf8(instance_id)
     return hmac.new(secret, instance_id, hashlib.sha256).hexdigest()
+
+
+def parse_permitted_ethertypes(permitted_ethertypes):
+    ret = set()
+    for pe in permitted_ethertypes:
+        if pe[:2].lower() != '0x':
+            LOG.warning('Custom ethertype %s is not a hexadecimal number.', pe)
+            continue
+
+        try:
+            value = hex(int(pe, 16))
+            if value in ret:
+                LOG.warning('Custom ethertype %s is repeated', pe)
+            else:
+                ret.add(value)
+        except ValueError:
+            LOG.warning('Custom ethertype %s is not a hexadecimal number.', pe)
+            continue
+
+    return ret
diff --git a/neutron/tests/unit/common/test_utils.py b/neutron/tests/unit/common/test_utils.py
index 5c110c60298..4453fcf1707 100644
--- a/neutron/tests/unit/common/test_utils.py
+++ b/neutron/tests/unit/common/test_utils.py
@@ -656,3 +656,24 @@ class SignatureTestCase(base.BaseTestCase):
             '773ba44693c7553d6ee20f61ea5d2757a9a4f4a44d2841ae4e95b52e4cd62db4',
             utils.sign_instance_id(conf, 'foo')
         )
+
+
+class ParsePermittedEthertypesTestCase(base.BaseTestCase):
+
+    @mock.patch.object(utils, 'LOG')
+    def test_parse_permitted_ethertypes(self, mock_log):
+        permitted_ethertypes = ['0x1234',
+                                '0x1234',
+                                '0x5678',
+                                '0XCAfe',
+                                '1112',
+                                '0x123R']
+        ret = utils.parse_permitted_ethertypes(permitted_ethertypes)
+        self.assertEqual({'0x1234', '0x5678', '0xcafe'}, ret)
+        calls = [mock.call('Custom ethertype %s is repeated', '0x1234'),
+                 mock.call('Custom ethertype %s is not a hexadecimal number.',
+                           '1112'),
+                 mock.call('Custom ethertype %s is not a hexadecimal number.',
+                           '0x123R'),
+                 ]
+        mock_log.warning.assert_has_calls(calls)