arp - "permanent"输出中的 "arp -a"字是什么意思？

Question

我正在尝试学习 ARP 协议(protocol)。我对 ARP 的看法是，它是一种有助于将 IP 寻址到确切 MAC 地址的协议(protocol)。

但是当我尝试这样做时:

arp -a

我认为它将显示 IP 地址列表和匹配的 MAC 地址。在看到 permanent 这个词之前，我什么都懂.其他行标记为 ifscope , 一个标记为 permanent .

谁能告诉我是什么意思 permanent ?为什么这条线不一样？

提前致谢。

Answer 1

根据TCP/IP Guide :

There are two different ways that cache entries can be put into the ARP cache:

• Static ARP Cache Entries: These are address resolutions that are manually added to the cache table for a device and are kept in the cache on a permanent basis. Static entries are typically managed using a tool such as the arp software utility.

• Dynamic ARP Cache Entries: These are hardware/IP address pairs that are added to the cache by the software itself as a result of successfully-completed past ARP resolutions. They are kept in the cache only for a period of time and are then removed.

所以这个词 permanent在 arp -a output 表示该条目被手动添加到缓存中(静态)。