|  | 9.2 | Layer 3 Concepts
| 9.2.4 | How ARP works
| PowerPoint® Presentation (Microsoft PowerPoint 2000, 342KB)
| This PowerPoint Presentation explains the Address Resolution Protocol (ARP) determination process. Note: In Internet Explorer, right click on the PowerPoint presentation to view it full screen.
ARP is used to resolve or map a known IP address to a MAC sublayer address in order to allow communication on a multi-access medium such as Ethernet. To determine a destination MAC address for a datagram, a table called the ARP cache is checked. If the address is not in the table, ARP sends a broadcast that will be received by every station on the network, looking for the destination station. The term "local ARP" is used to describe the search for an address when the requesting host and the destination host share the same medium or wire. As shown in the Figure , prior to issuing the ARP, the subnet mask must be consulted. In this case, the mask determines that the nodes are on the same subnet.
| Lab Activity
| In this lab you will view the ARP table stored in the router and clear the router’s ARP table. These two commands are very important in troubleshooting a network problem.

| Lab Activity

You and your group have been assigned to help a system administrator of a network for XYZ company. The system administrator of this network would like to know the MAC addresses of each of the Ethernet interfaces on the routers.