Appendix G

ARP Program

ARP is the Internet layer protocol responsible for matching or obtaining the MAC (hardware) address that corresponds to a particular IP address. The ARP command allows the user to view the current contents of the ARP cache of the local computer (residing on the same network) or remote computer (residing on the different network) through a router.

Microsoft includes the ARP.EXE utility for viewing and modifying the ARP cache with its Windows products. The following ARP commands can be used to view cache entries:

arp –afi Use this command to view all ARP cache entries.

arp –aplus IP address fi Use this command to view ARP cache entries associated with one particular interface on a network with multiple adapters.

arp –g fi Same as arp –a.

arp –Nfi Use this command to display ARP entries for specific network interface.

arp – s plus IP address plus Physical address fi Use this command to manually add a permanent static entry to the ARP cache.

arp –dfi Use this command to manually delete a static entry.

Ping the destination computer using IP address first before using the arp -acommand.

The following window shows examples of arp commands and responses.

• Your computer has an IP address of 192.168.1.118

• The destination computer has an IP address of

192.168.1.96

Figure G-1 ARP Commands and Responses

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Omega C4EIT/-EIT manual Arp -g fi Same as arp -a, 192.168.1.96, Appendix G ARP Program