def node_is_reachable(src_node, dst_node):
    """
    Returns true if a node is unreachable from another node.

    :param src_node:        The source node to check from reachability from.
    :param dst_node:        The destination node to check for reachability to.
    :return:                True only if dst is reachable from src.
    """
    return 0 == src_node.account.ssh("nc -w 3 -z %s 22" % dst_node.account.hostname, allow_fail=True)