ARP（Address Resolution Protocol，地址解析协议） 是一个通过解析 网络层地址 来找寻 数据链路层 地址的网络传输协议，它在IPv4中极其重要。
ARP
arping 命令可以发起 ARP 报文，ARP 的交互过程：
- To: everybody (ff:ff:ff:ff:ff:ff). I am looking for the computer who has IP address 172.20.0.20. Signed: MAC address 00:0c:29:4a:1a:f0.
- Host B responds with a response like this: To: 00:0c:29:4a:1a:f0. I have IP address 172.20.0.20. Signed: MAC address 52:54:00:0f:d0:15.