ARP which means Address Resolution Protocol manipulates the kernel's ARP cache in different ways. the main option is to clear an address mapping entry and manually setting up one.

the ARP protocol is for enabling a host (Computer or PC) to send a broadcast query (a query is a message that goes out to all the computers connected to the Local Network (LAN), the query is asking the computer that has a given IP address to identify itself to other computers in the same local network. this ip address is also logged in your computer.

you can see your ARP table to see which computers have communicated with you computer, if you are using a windows computer like me (windows xp) you can open the DOS Terminal and send this command

apr -a

you will get a list of all the misaddresses that are mapped to a MAC address

you can get more information about the arp command if you send this command in your DOS terminal: 

Displays and modifies the IP-to-Physical address translation tables used by
address resolution protocol (ARP).

ARP -s inet_addr eth_addr [if_addr]
ARP -d inet_addr [if_addr]
ARP -a [inet_addr] [-N if_addr] [-v]

  -a            Displays current ARP entries by interrogating the current
                protocol data.  If inet_addr is specified, the IP and Physical
                addresses for only the specified computer are displayed.  If
                more than one network interface uses ARP, entries for each ARP
                table are displayed.
  -g            Same as -a.
  -v            Displays current ARP entries in verbose mode.  All invalid
                entries and entries on the loop-back interface will be shown.
  inet_addr     Specifies an internet address.
  -N if_addr    Displays the ARP entries for the network interface specified
                by if_addr.
  -d            Deletes the host specified by inet_addr. inet_addr may be
                wildcarded with * to delete all hosts.
  -s            Adds the host and associates the Internet address inet_addr
                with the Physical address eth_addr.  The Physical address is
                given as 6 hexadecimal bytes separated by hyphens. The entry
                is permanent.
  eth_addr      Specifies a physical address.
  if_addr       If present, this specifies the Internet address of the
                interface whose address translation table should be modified.
                If not present, the first applicable interface will be used.
Example:
  > arp -s 157.55.85.212   00-aa-00-62-c6-09  .... Adds a static entry.
  > arp -a                                    .... Displays the arp table.