code: def configExternalRouter(self, P_Prefix, P_stable, R_Preference=0):
          
          print '%s call configExternalRouter' % self.port
          print P_Prefix
          stable = ''
          prefix = self.__convertIp6PrefixStringToIp6Address(str(P_Prefix))
          try:
              if R_Preference == 1:
                  prf = 'high'
              elif R_Preference == 0:
                  prf = 'med'
              elif R_Preference == -1:
                  prf = 'low'
              else:
                  pass
  
              if P_stable:
                  stable += 's'
                  cmd = 'route add %s/64 %s %s' % (prefix, stable, prf)
              else:
                  cmd = 'route add %s/64 %s' % (prefix, prf)
              print cmd
  
              if self.__sendCommand(cmd)[0] == 'Done':
                  # send server data ntf to leader
                  return self.__sendCommand('netdataregister')[0] == 'Done'
          except Exception, e:
              ModuleHelper.WriteIntoDebugLogger("configExternalRouter() Error: " + str(e))
docs: configure border router with a given external route prefix entry
  
          Args:
              P_Prefix: IPv6 prefix for the route
              P_Stable: is true if the external route prefix is stable network data
              R_Preference: a two-bit signed integer indicating Router preference
                            1: high
                            0: medium
                           -1: low
  
          Returns:
              True: successful to configure the border router with a given external route prefix
              False: fail to configure the border router with a given external route prefix