unreachable destination

基本解释

You can probably guess what a "destination unreachable attack" will be like.
您可能会猜想“目的地不可到达攻击”会是什么情形。
Otherwise, the messages would remain on the Exchange server mail queue as "destination unreachable."
否则，由于 “destination unreachable”，邮件会留在 Exchange 服务器邮件队列中。
If an intruder gained access to a host in Network 10.1.0.0, he could broadcast a "Destination Unreachable Message" stating that Gateway G is not reachable to all hosts in the network he is in.
如果入侵者获得了网络 10.1.0.0 中一台主机的访问权，那么，他可以广播一条“目的地不可到达消息”，声明网关 G 对于他所在网络的所有主机是不可到达的。