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:
DESCRIPTION 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: 192.168.1.49 --- 0xb Internet Address Physical Address Type 192.168.1.29 00-1d-92-08-49-25 dynamic 192.168.1.34 00-24-81-85-ab-b6 dynamic
To clear the cache
C:\>netsh interface ip delete arpcache Ok.
To show the arp cache on a nix machine:
$ arp -vn; cat /proc/net/arp Address HWtype HWaddress Flags Mask Iface 192.168.1.254 ether 00:08:ae:09:20:a0 C eth0 IP address HW type Flags HW address Mask Device 192.168.1.254 0x1 0x2 00:08:ae:09:20:a0 * eth0
To clear the apr cache on a nix machine.
$ ip neigh flush all