diff --git a/vlanmang.py b/vlanmang.py
index 5a314b7..d3413b1 100644
--- a/vlanmang.py
+++ b/vlanmang.py
@@ -59,6 +59,14 @@ def checkchanges(module):
 	for i in mods:
 		switch = SNMPSwitch(i.host, i.community)
 		portmapping = switch.getportmapping()
+		invportmap = { y: x for x, y in portmapping.iteritems() }
+
+		portlist = getportlist(i._vlanconf, invportmap.__getitem__)
+
+		ports = set(portmapping.iterkeys())
+
+		if ports != portlist:
+			raise ValueError('missing or extra ports found: %s' % `ports.symmetric_difference(portlist)`)
 
 def getpvidmapping(data, lookupfun):
 	'''Return a mapping from vlan based table to a port: vlan
@@ -166,7 +174,7 @@ class SNMPSwitch(object):
 		'''Return a port name mapping.  Keys are the port index
 		and the value is the name from the ifName entry.'''
 
-		return dict((x[0][-1], str(x[1])) for x in self._walk('IF-MIB', 'ifName'))
+		return { x[0][-1]: str(x[1]) for x in self._walk('IF-MIB', 'ifName') }
 
 	def findport(self, name):
 		'''Look up a port name and return it's port index.  This
@@ -193,16 +201,23 @@ class SNMPSwitch(object):
 		    int(vlan)), 6) # destroy(6)
 
 	def getvlans(self):
-		'''Return all the vlans.'''
+		'''Return an iterator with all the vlan ids.'''
 
 		return (x[0][-1] for x in self._walk('Q-BRIDGE-MIB', 'dot1qVlanStatus'))
 
 	def staticvlans(self):
-		'''Return the staticly defined/configured vlans.  This
-		sometimes excludes special built in vlans, like vlan 1.'''
+		'''Return an iterator of the staticly defined/configured
+		vlans.  This sometimes excludes special built in vlans,
+		like vlan 1.'''
 
 		return (x[0][-1] for x in self._walk('Q-BRIDGE-MIB', 'dot1qVlanStaticName'))
 
+	def getpvid(self):
+		'''Returns a dictionary w/ the interface index as the key,
+		and the pvid of the interface.'''
+
+		return { x[0][-1]: int(x[1]) for x in self._walk('Q-BRIDGE-MIB', 'dot1qPvid') }
+
 class _TestMisc(unittest.TestCase):
 	def setUp(self):
 		import test_data
@@ -242,16 +257,24 @@ class _TestMisc(unittest.TestCase):
 	@mock.patch('importlib.import_module')
 	def test_checkchanges(self, imprt, portmapping):
 		def tmp(*args, **kwargs):
-			print `args`
 			return self._test_data
 		imprt.side_effect = tmp
 
-		checkchanges('data')
+		ports = { x: 'g%d' % x for x in xrange(1, 24) }
+		ports[30] = 'lag1'
+		ports[31] = 'lag2'
+		portmapping.side_effect = [ ports, ports ]
+
+		self.assertRaises(ValueError, checkchanges, 'data')
 
 		imprt.assert_called_with('data')
 		portmapping.assert_called()
 
-_skipSwitchTests = True
+		del ports[31]
+
+		checkchanges('data')
+
+_skipSwitchTests = False
 
 class _TestSwitch(unittest.TestCase):
 	def setUp(self):
@@ -294,6 +317,10 @@ class _TestSwitch(unittest.TestCase):
 
 		self.assertTrue(set(switch.staticvlans()).issubset(existingvlans))
 
+		pvidres = { x: 1 for x in xrange(1, 9) }
+		pvidres.update({ x: 1 for x in xrange(14, 18) })
+		self.assertEqual(switch.getpvid(), pvidres)
+
 		testname = 'Sometestname'
 
 		# Create test vlan