diff --git a/src/python/oftest/testutils.py b/src/python/oftest/testutils.py
index bf2b24a..e87b7a0 100644
--- a/src/python/oftest/testutils.py
+++ b/src/python/oftest/testutils.py
@@ -1598,4 +1598,17 @@
 
     test.assertTrue(msg == None, "Did not expect a packet-in message on port %d" % in_port)
 
+def openflow_ports(num=None):
+    """
+    Return a list of 'num' OpenFlow port numbers
+
+    If 'num' is None, return all available ports. Otherwise, limit the length
+    of the result to 'num' and raise an exception if not enough ports are
+    available.
+    """
+    ports = sorted(oftest.config["port_map"].keys())
+    if num != None and len(ports) < num:
+        raise Exception("test requires %d ports but only %d are available" % (num, len(ports)))
+    return ports[:num]
+
 __all__ = list(set(locals()) - _import_blacklist)