4.8 arp Command

4.8 arp Command

We've used this command with the -a flag to display all the entries in the ARP cache. Other options are provided.

The superuser can specify the -d option to delete an entry from the ARP cache. (This was used before running a few of the examples, to let us see the ARP exchange.)

Entries can also be added using the -s option. It requires a hostname and an Ethernet address: the IP address corresponding to the hostname, and the Ethernet address are added to the cache. This entry is made permanent (i.e., it won't time out from the cache) unless the keyword temp appears at the end of the command line.

The keyword pub at the end of a command line with the -s option causes the system to act as an ARP agent for that host. The system will answer ARP requests for the IP address corresponding to the hostname, replying with the specified Ethernet address. If the advertised address is the system's own, then this system is acting as a proxy ARP agent for the specified hostname.