diff --git a/ryu/services/protocols/bgp/base.py b/ryu/services/protocols/bgp/base.py
index 5e4cc254..9d23adb7 100644
--- a/ryu/services/protocols/bgp/base.py
+++ b/ryu/services/protocols/bgp/base.py
@@ -20,6 +20,7 @@ from __future__ import absolute_import
 import abc
 from collections import OrderedDict
 import logging
+import six
 import socket
 import time
 import traceback
@@ -125,6 +126,7 @@ class ActivityException(BGPSException):
     pass
 
 
+@six.add_metaclass(abc.ABCMeta)
 class Activity(object):
     """Base class for a thread of execution that provides some custom settings.
 
@@ -133,7 +135,6 @@ class Activity(object):
     to start another activity or greenthread. Activity is also holds pointers
     to sockets that it or its child activities of threads have create.
     """
-    __metaclass__ = abc.ABCMeta
 
     def __init__(self, name=None):
         self._name = name
diff --git a/ryu/services/protocols/bgp/info_base/base.py b/ryu/services/protocols/bgp/info_base/base.py
index 939cf3c8..54e02bb5 100644
--- a/ryu/services/protocols/bgp/info_base/base.py
+++ b/ryu/services/protocols/bgp/info_base/base.py
@@ -25,6 +25,7 @@ from copy import copy
 import logging
 import functools
 import netaddr
+import six
 
 from ryu.lib.packet.bgp import RF_IPv4_UC
 from ryu.lib.packet.bgp import RouteTargetMembershipNLRI
@@ -43,6 +44,7 @@ from ryu.services.protocols.bgp.processor import BPR_UNKNOWN
 LOG = logging.getLogger('bgpspeaker.info_base.base')
 
 
+@six.add_metaclass(ABCMeta)
 class Table(object):
     """A container for holding information about destination/prefixes.
 
@@ -50,7 +52,6 @@ class Table(object):
     This is a base class which should be sub-classed for different route
     family. A table can be uniquely identified by (Route Family, Scope Id).
     """
-    __metaclass__ = abc.ABCMeta
     ROUTE_FAMILY = RF_IPv4_UC
 
     def __init__(self, scope_id, core_service, signal_bus):
@@ -275,6 +276,7 @@ class NonVrfPathProcessingMixin(object):
                 self._sent_routes = {}
 
 
+@six.add_metaclass(ABCMeta)
 class Destination(object):
     """State about a particular destination.
 
@@ -282,7 +284,6 @@ class Destination(object):
     a routing information base table *Table*.
     """
 
-    __metaclass__ = abc.ABCMeta
     ROUTE_FAMILY = RF_IPv4_UC
 
     def __init__(self, table, nlri):
@@ -665,13 +666,13 @@ class Destination(object):
         return result
 
 
+@six.add_metaclass(ABCMeta)
 class Path(object):
     """Represents a way of reaching an IP destination.
 
     Also contains other meta-data given to us by a specific source (such as a
     peer).
     """
-    __metaclass__ = ABCMeta
     __slots__ = ('_source', '_path_attr_map', '_nlri', '_source_version_num',
                  '_exported_from', '_nexthop', 'next_path', 'prev_path',
                  '_is_withdraw', 'med_set_by_target_neighbor')
@@ -835,6 +836,7 @@ class Path(object):
             self._path_attr_map, self._nexthop, self._is_withdraw))
 
 
+@six.add_metaclass(ABCMeta)
 class Filter(object):
     """Represents a general filter for in-bound and out-bound filter
 
@@ -845,7 +847,6 @@ class Filter(object):
     ================ ==================================================
 
     """
-    __metaclass__ = ABCMeta
 
     ROUTE_FAMILY = RF_IPv4_UC
 
diff --git a/ryu/services/protocols/bgp/info_base/vpn.py b/ryu/services/protocols/bgp/info_base/vpn.py
index e5cdef4d..0f591070 100644
--- a/ryu/services/protocols/bgp/info_base/vpn.py
+++ b/ryu/services/protocols/bgp/info_base/vpn.py
@@ -19,6 +19,7 @@
 
 import abc
 import logging
+import six
 
 from ryu.services.protocols.bgp.info_base.base import Destination
 from ryu.services.protocols.bgp.info_base.base import NonVrfPathProcessingMixin
@@ -55,8 +56,8 @@ class VpnTable(Table):
         )
 
 
+@six.add_metaclass(abc.ABCMeta)
 class VpnPath(Path):
-    __metaclass__ = abc.ABCMeta
     ROUTE_FAMILY = None
     VRF_PATH_CLASS = None
     NLRI_CLASS = None
@@ -82,11 +83,10 @@ class VpnPath(Path):
         return vrf_path
 
 
+@six.add_metaclass(abc.ABCMeta)
 class VpnDest(Destination, NonVrfPathProcessingMixin):
     """Base class for VPN destinations."""
 
-    __metaclass__ = abc.ABCMeta
-
     def _best_path_lost(self):
         old_best_path = self._best_path
         NonVrfPathProcessingMixin._best_path_lost(self)
diff --git a/ryu/services/protocols/bgp/info_base/vrf.py b/ryu/services/protocols/bgp/info_base/vrf.py
index 0c7d60cd..c3f6603c 100644
--- a/ryu/services/protocols/bgp/info_base/vrf.py
+++ b/ryu/services/protocols/bgp/info_base/vrf.py
@@ -19,6 +19,7 @@
 
 import abc
 import logging
+import six
 
 from ryu.lib.packet.bgp import BGP_ATTR_TYPE_ORIGIN
 from ryu.lib.packet.bgp import BGP_ATTR_TYPE_AS_PATH
@@ -44,12 +45,12 @@ from ryu.services.protocols.bgp.utils.stats import RESOURCE_NAME
 LOG = logging.getLogger('bgpspeaker.info_base.vrf')
 
 
+@six.add_metaclass(abc.ABCMeta)
 class VrfTable(Table):
     """Virtual Routing and Forwarding information base.
      Keeps destination imported to given vrf in represents.
      """
 
-    __metaclass__ = abc.ABCMeta
     ROUTE_FAMILY = None
     VPN_ROUTE_FAMILY = None
     NLRI_CLASS = None
@@ -273,9 +274,9 @@ class VrfTable(Table):
         return super(VrfTable, self).clean_uninteresting_paths(interested_rts)
 
 
+@six.add_metaclass(abc.ABCMeta)
 class VrfDest(Destination):
     """Base class for VRF destination."""
-    __metaclass__ = abc.ABCMeta
 
     def __init__(self, table, nlri):
         super(VrfDest, self).__init__(table, nlri)
@@ -424,11 +425,11 @@ class VrfDest(Destination):
                              'with attribute label_list got %s' % path)
 
 
+@six.add_metaclass(abc.ABCMeta)
 class VrfPath(Path):
     """Represents a way of reaching an IP destination with a VPN.
     """
     __slots__ = ('_label_list', '_puid')
-    __metaclass__ = abc.ABCMeta
 
     ROUTE_FAMILY = None
     VPN_PATH_CLASS = None
diff --git a/ryu/services/protocols/bgp/protocol.py b/ryu/services/protocols/bgp/protocol.py
index 43f45347..79283059 100644
--- a/ryu/services/protocols/bgp/protocol.py
+++ b/ryu/services/protocols/bgp/protocol.py
@@ -19,8 +19,10 @@
 
 from abc import ABCMeta
 from abc import abstractmethod
+import six
 
 
+@six.add_metaclass(ABCMeta)
 class Protocol(object):
     """Interface for various protocols.
 
@@ -31,7 +33,6 @@ class Protocol(object):
     facilitate or provide hooks to sub-classes to override behavior as
     appropriate.
     """
-    __metaclass__ = ABCMeta
 
     @abstractmethod
     def data_received(self, data):
@@ -62,12 +63,12 @@ class Protocol(object):
         pass
 
 
+@six.add_metaclass(ABCMeta)
 class Factory(object):
     """This is a factory which produces protocols.
 
     Can also act as context for protocols.
     """
-    __metaclass__ = ABCMeta
 
     # Put a subclass of Protocol here:
     protocol = None
diff --git a/ryu/services/protocols/bgp/rtconf/base.py b/ryu/services/protocols/bgp/rtconf/base.py
index 0ea026de..c61798dc 100644
--- a/ryu/services/protocols/bgp/rtconf/base.py
+++ b/ryu/services/protocols/bgp/rtconf/base.py
@@ -143,13 +143,13 @@ class ConfigValueError(RuntimeConfigError):
 # Configuration base classes.
 # =============================================================================
 
+@six.add_metaclass(ABCMeta)
 class BaseConf(object):
     """Base class for a set of configuration values.
 
     Configurations can be required or optional. Also acts as a container of
     configuration change listeners.
     """
-    __metaclass__ = ABCMeta
 
     def __init__(self, **kwargs):
         self._req_settings = self.get_req_settings()
@@ -426,9 +426,9 @@ class ConfWithStats(BaseConf):
                                   **kwargs)
 
 
+@six.add_metaclass(ABCMeta)
 class BaseConfListener(object):
     """Base class of all configuration listeners."""
-    __metaclass__ = ABCMeta
 
     def __init__(self, base_conf):
         pass