Adds a network to be advertised by OSPF

           Args:
               network (str):  The network to be advertised in dotted decimal
                               notation
               netmask (str):  The netmask to configure
               area (str):  The area the network belongs to.
                            By default this value is 0
           Returns:
               bool: True if the command completes successfully
           Exception:
               ValueError: This will get raised if network or netmask
                           are not passed to the method

def add_network(self, network, netmask, area=0):
        """Adds a network to be advertised by OSPF

           Args:
               network (str):  The network to be advertised in dotted decimal
                               notation
               netmask (str):  The netmask to configure
               area (str):  The area the network belongs to.
                            By default this value is 0
           Returns:
               bool: True if the command completes successfully
           Exception:
               ValueError: This will get raised if network or netmask
                           are not passed to the method
        """
        if network == '' or netmask == '':
            raise ValueError('network and mask values '
                             'may not be empty')
        cmd = 'network {}/{} area {}'.format(network, netmask, area)
        return self.configure_ospf(cmd)