Showing (and/or) Clearing the arp cache

The arp cache should (normally) be cleared within 20 minutes (or less, this depends on what platform is used).

If you don’t know what ARP is and what is is good for, then perhaps you should take a moment and read the man page:

Arp manipulates or displays the kernels IPv4 network neighbor cache. It can add entries to the table, delete one or display the current content.
ARP stands for Address Resolution Protocol, which is used to find the media access control address of a network neighbor for a given IPv4 Address.

On a windows platform to show the arp cache

C:\> arp -a
Interface: --- 0xb
  Internet Address      Physical Address      Type          00-1d-92-08-49-25     dynamic          00-24-81-85-ab-b6     dynamic

To clear the cache

C:\>netsh interface ip delete arpcache

To show the arp cache on a nix machine:

$  arp -vn; cat /proc/net/arp
Address                  HWtype  HWaddress           Flags Mask            Iface            ether   00:08:ae:09:20:a0   C                     eth0
IP address       HW type     Flags       HW address            Mask     Device    0x1         0x2         00:08:ae:09:20:a0     *        eth0

To clear the apr cache on a nix machine.

$  ip neigh flush all