ARP table

The ARP table is a construct that is maintained within all network devices running IPv4 over a Layer 2 network technology such as Ethernet. The ARP table maintains an IP address to Layer 2 address mapping. When used with Ethernet, this is an IP address to MAC address mapping. A fully populated ARP table on a host contains the IP address to MAC address mappings of all IP addresses within the host's subnet.

All network devices that have an IP address including hosts, routers, switches, printers, IP cameras, wireless clients etc... maintain an ARP table.

On a Windows device, the ARP table can be viewed using the following command:

C:UsersH1>**arp -a** Interface: --- 0xb   Internet Address      Physical Address      Type          00-0c-29-63-af-d0     dynamic   192.168.1 .255       ff-ff-ff-ff-ff-ff     static            01-00-5e-00-00-16     static           01-00-5e-00-00-fc     static       01-00-5e-7f-ff-fa     static       ff-ff-ff-ff-ff-ff     static

The following is an example of an ARP table from a Cisco IOS device:

Router# show ip arp Protocol  Address       Age(min)Hardware Addr  Type Interface Internet 9       0000.0c59.f892 ARPA Ethernet0/0 Internet 8       0000.0c07.ac00 ARPA Ethernet0/0

ARP entries are maintained within the table for a specific amount of time