def get_net_uuid(neutron_client, net_name):
    """Determine whether deprecated external network mode is in use.

    :param neutron_client: Authenticated neutronclient
    :type neutron_client: neutronclient.Client object
    :param net_name: Network name
    :type net_name: string
    :returns: Network ID
    :rtype: string
    """
    network = neutron_client.list_networks(name=net_name)['networks'][0]
    return network['id']