ARP Command – Address Resolution Protocol
ARP command can display and modify the IP-to-Physical address translation tables used by address resolution protocol.
Syntax
View the contents of the local ARP cache table
ARP -a [inet_addr] [-N if_addr] [-v]
Add a static Arp entry for frequent accessed hosts
ARP -s inet_addr eth_addr [if_addr]
Delete an entry
ARP -d inet_addr [if_addr]
Key
| -a |
Display current ARP entries. May include more than one network interface. If inet_addr is specified, the IP and Physical addresses for only the specified computer are displayed. |
| -g | Same as -a. |
| -N |
if_addr Display the ARP entries for the network interface specified by if_addr. |
| -d |
inet_addr Delete the host specified by inet_addr or wildcard * will delete all hosts. |
| -s |
Add 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. |
Note:
If two hosts on the same network(Subnet) cannot ping each other, try using ARP -a to list the addresses on each computer to see if they have the correct MAC addresses.
A host’s MAC address can be checked using IPCONFIG. If another host with a duplicate IP address exists on the network, the ARP cache may have had the MAC address for the other computer placed in it. ARP -d is used to delete an entry that may be incorrect.
Examples
ARP command to display the ARP cache tables for all interfaces:
C:\> arp -a
ARP command to display the ARP cache table for the interface on IP address 10.0.0.5
C:\> arp -a -N 10.0.0.5
Add a static ARP cache entry on IP addr 10.1.1.5 to the physical address 00-AA-21-5A-3A-7B
C:\> arp -s 10.1.1.5 00-AA-21-5A-3A-7B