The ARP Utility

The ARP Utility

As mentioned earlier, ARP is used by the IP address to identify the MAC address of a device present on the same subnet. The TCP/IP first searches MAC address in its own ARP table in case a TCP/IP device is required to forward a packet to a device in a local subnet. The first search is always performed in its own ARP table as the contents are periodically managed. This search is carried for the association between the known IP address of the destination device on the local subnet and the MAC address of the same device. If the IP address of the destination device does not associate with the MAC address, then the destination device sends the request for an ARP broadcast. This ARP broadcast contains MAC and IP addresses of the source device along with the IP address and blank MAC address field of destination device. ARP utility allows you to determine the ARP cache of operating system. To view this, you need to type the ARP command on the DOS prompts.

For example:



Option Description
Inte_addr Defines an Internet address.
-a Allows you to show the current ARP entries by searching the current protocol data. If the Internet address is specified, the IP and physical addresses of the specified computers are displayed. When more than one network interface use the ARP, entries of all ARP table are displayed.
-g Similar to the function of -a.
-v Shows current ARP entries in verbose mode as well as displays all invalid entries and entries on the loopback interface.
eth_addr Defines a physical address.
-d Allows you to delete the host that is defined by an  internet address To delete all host, you need*wildcard
-s Allows you to add a new host along with its related internet address and physical address.
If_addr Is an option function. If the option is present, it specifies the internet address of the network interface whose address translation table must be modified. If the option is not present, the first valid interface will be used.
-N if_addr Displays the ARP entries for the network interface specified by if_addr.


The ARP utility is also use d for resolving duplicate IP address

To display the entire current ARP table use the following ARP command with the -a option

arp -a

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