Cisco Catalyst 3750-E Series, Software Configuration Manual

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Catalyst 3750-E and 3560-E Switch Software Configuration Guide
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Chapter 7 Administering the Switch
Managing the ARP Table
Managing the ARP Table
To communicate with a device (over Ethernet, for example), the software first must learn the 48-bit MAC
address or the local data link address of that device. The process of learning the local data link address
from an IP address is called
address resolution .
The Address Resolution Protocol (ARP) associates a host IP address with the corresponding media or
MAC addresses and the VLAN ID. Using an IP address, ARP finds the associated MAC address. When
a MAC address is found, the IP-MAC address association is stored in an ARP cache for rapid retrieval.
Then the IP datagram is encapsulated in a link-layer frame and sent over the network. Encapsulation of
IP datagrams and ARP requests and replies on IEEE 802 networks other than Ethernet is specified by
the Subnetwork Access Protocol (SNAP). By default, standard Ethernet-style ARP encapsulation
(represented by the
arpa keyword) is enabled on the IP interface.
ARP entries added manually to the table do not age and must be manually removed.
For CLI procedures, see the Cisco IOS Release 12.2 documentation on Cisco.com.