R1 sends a packet with the destination IP and MAC address of R2, when the local switch receives the frame, it looks at the destination MAC address and looks up the MAC address in the cam table (also known as mac-address table). When it finds the matching MAC address and associated switch port and then forwards the frame out the correct port to get to the destination MAC address.
However, sometimes ARP is not always reliable and in some special scenarios routers and/or switches cannot learn the MAC address of a directly or indirectly connected host. Such as a virtual machine or a host that does not reply to ARP request for whatever reason. In this case a static ARP entry is necessary to ensure efficient layer two communications.
Configure a static ARP entry on R1 with the IP address 10.1.1.25 and the mac address 00ac.a1f3.01ab
R1>enable
R1#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
R1(config)#arp 10.1.1.25 00ac.a1f3.01ab arpa
R1(config)#end
ARPA stands for Advanced Research Projects Agency for those who are curious as to what arpa stands for at the end of the static ARP statement. ARPA developed the Ethernet II frame which is currently used by the Internet Protocol.
R1#show arp
Protocol Address Age (min) Hardware Addr Type Interface
Internet 10.1.1.1 - ca00.0d78.0008 ARPA FastEthernet0/0
Internet 10.1.1.25 - 00ac.a1f3.01ab ARPA
Source: http://www.freeccnaworkbook.com
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