arp

The arp command displays and modifies entries in the Address Resolution Protocol (ARP) cache. The ARP cache contains one or more tables that are used to store IP addresses and their resolved Ethernet or Token Ring physical addresses. There's a separate table for each Ethernet or Token Ring network adapter installed on your computer.

Syntax

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

Parameters

Parameter	Description
-a	Displays the current ARP entries by querying the protocol data. If inet_addr is specified, only the ARP entry for that IP address is shown. If multiple network interfaces use ARP, entries for each interface are displayed.
-g	Functions identically to -a.
-v	Displays ARP entries in verbose mode, including additional details such as invalid entries and entries on the loopback interface.
inet_addr	Specifies the IP address to display, delete, or add to the ARP cache. In the context of -s, it's the IP you want to associate with a MAC address.
-N if_addr	Shows ARP entries for the network interface with the specified IP address (if_addr). This parameter is case-sensitive.
-d	Deletes the ARP entry for the specified inet_addr. Use * as a wildcard to delete all entries.
-s	Adds a static ARP entry, associating inet_addr with the physical address eth_addr. Optionally, specify if_addr to add the entry to a specific interface. The entry is permanent until the TCP/IP stack is restarted.
eth_addr	Specifies the physical (MAC) address to associate with the IP address when using -s. The format is six hexadecimal bytes separated by hyphens.
if_addr	Specifies the IP address of the network interface whose ARP table is to be modified, used optionally with -s and -d. If omitted, the first applicable interface is used.
/?	Displays help at the command prompt.

Remarks

• The IP addresses for inetaddr and ifaceaddr are expressed in dotted decimal notation (for example, 10.0.0.1).

• The physical MAC address for etheraddr consists of six bytes expressed in hexadecimal notation and separated by hyphens (for example, 00-AA-00-4F-2A-9C).

• Entries added with the -s parameter are removed if the TCP/IP protocol is stopped and started. To create permanent static arp cache entries, place the appropriate arp commands in a batch file and use Scheduled Tasks to run the batch file at startup.

Examples

To display the arp cache tables for all interfaces, type:

arp -a

To display the arp cache table for the interface where the IP address 10.0.0.99 is assigned, type:

arp -a -N 10.0.0.99

To add a static arp cache entry that resolves the IP address 10.0.0.80 to the physical address 00-AA-00-4F-2A-9C, type:

arp -s 10.0.0.80 00-AA-00-4F-2A-9C

Related links

• Command-Line Syntax Key