'Create a switch instance
Additional options over superclass:
log_level (default to default_log_level) is level for this instance
ports is a list of interface names'

def __init__(self, **kw):

    log_level = kw.pop('log_level', self.default_log_level)
    self.q = Queue()
    self.t = Thread(target=self._consumer_threadproc)
    core.addListeners(self)
    ports = kw.pop('ports', [])
    kw['ports'] = []
    super(PCapSwitch, self).__init__(**kw)
    self._next_port = 1
    self.px = {}
    for p in ports:
        self.add_interface(p, start=False)
    self.log.setLevel(log_level)
    for px in self.px.itervalues():
        px.start()
    self.t.start()
