diff --git a/nova/network/manager.py b/nova/network/manager.py
index 0e652c6107e7..621744f6c73c 100644
--- a/nova/network/manager.py
+++ b/nova/network/manager.py
@@ -293,10 +293,10 @@ class FloatingIP(object):
                     LOG.debug(msg)
                     continue
                 fixed_address = fixed_ip_ref['address']
-                interface = floating_ip['interface']
+                interface = FLAGS.public_interface or floating_ip['interface']
                 try:
                     self.l3driver.add_floating_ip(floating_ip['address'],
-                            fixed_address, floating_ip['interface'])
+                            fixed_address, interface)
                 except exception.ProcessExecutionError:
                     LOG.debug(_('Interface %(interface)s not found'), locals())
                     raise exception.NoFloatingIpInterface(interface=interface)
@@ -476,7 +476,7 @@ class FloatingIP(object):
         else:
             host = network['host']
 
-        interface = floating_ip['interface']
+        interface = FLAGS.public_interface or floating_ip['interface']
         if host == self.host:
             # i'm the correct host
             self._associate_floating_ip(context, floating_address,
@@ -547,7 +547,7 @@ class FloatingIP(object):
         else:
             host = network['host']
 
-        interface = floating_ip['interface']
+        interface = FLAGS.public_interface or floating_ip['interface']
         if host == self.host:
             # i'm the correct host
             self._disassociate_floating_ip(context, address, interface)
diff --git a/nova/tests/network/test_manager.py b/nova/tests/network/test_manager.py
index de8779be1d17..da892eddda2e 100644
--- a/nova/tests/network/test_manager.py
+++ b/nova/tests/network/test_manager.py
@@ -716,11 +716,24 @@ class VlanNetworkTestCase(test.TestCase):
         self.stubs.Set(self.network.db, 'fixed_ip_get', fixed_ip_get)
 
         self.mox.StubOutWithMock(self.network.l3driver, 'add_floating_ip')
+        self.flags(public_interface=False)
         self.network.l3driver.add_floating_ip('fakefloat',
                                               'fakefixed',
                                               'fakeiface')
         self.mox.ReplayAll()
         self.network.init_host_floating_ips()
+        self.mox.UnsetStubs()
+        self.mox.VerifyAll()
+
+        self.mox.StubOutWithMock(self.network.l3driver, 'add_floating_ip')
+        self.flags(public_interface='fooiface')
+        self.network.l3driver.add_floating_ip('fakefloat',
+                                              'fakefixed',
+                                              'fooiface')
+        self.mox.ReplayAll()
+        self.network.init_host_floating_ips()
+        self.mox.UnsetStubs()
+        self.mox.VerifyAll()
 
     def test_disassociate_floating_ip(self):
         ctxt = context.RequestContext('testuser', 'testproject',