Cisco WS-C2950T-24 Software Guide - Page 160
Managing the ARP Table
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Managing the ARP Table Chapter 6 Configuring the System Managing the ARP Table To communicate with a device (over Ethernet, for example), the software first must determine the 48-bit MAC or the local data link address of that device. The process of determining 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. Taking an IP address as input, ARP determines the associated MAC address. Once a MAC address is determined, 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, refer to the Cisco IOS Release 12.0 documentation on Cisco.com for additional information and CLI procedures. 6-32 Catalyst 2900 Series XL and Catalyst 3500 Series XL Software Configuration Guide 78-6511-08