def vni_row_name(network_type):
    """Determine name of row for VNI in allocations table.

    :param network_type: Network type to determine row name for.
    :type network_type: str
    :returns: Row name
    :rtype: str
    :raises: ValueError
    """
    if network_type in ('gre',):
        return '{}_id'.format(network_type)
    elif network_type in ('geneve', 'vxlan'):
        return '{}_vni'.format(network_type)
    raise ValueError('Unsupported network_type: {}'.format(network_type))