Table Of Contents
The ARP Optimization feature improves Address Resolution Protocol (ARP) performance by using an improved data structure to reduce ARP searching time.
Feature History for the ARP Optimization Feature
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Information About the ARP Optimization Feature
This section provides the following information about ARP optimization:
ARP Optimization Feature Design
ARP is used to map a Layer 3 IP address to a Layer 2 MAC address. A Cisco router stores this mapped information in an ARP table. The ARP table provides MAC rewrite information when the router is forwarding a packet using Cisco Express Forwarding (CEF) or other IP switching technologies.
In previous versions of Cisco IOS software, the ARP table was organized for easy searching on an entry based on the IP address. However, there are cases such as interface flapping on the router and a topology change in the network where all related ARP entries need to be refreshed for correct forwarding. This situation could consume a substantial amount of CPU time in the ARP process to search and clean up all the entries. The ARP Optimization feature improves ARP performance by reducing the ARP searching time by using an improved data structure.
No configuration tasks are associated with this feature.
ARP Optimization Benefits
This feature improves CPU utilization and provides a more efficient ARP table searching capability when a topology change occurs.
The following sections provide references related to the ARP Optimization feature.
Related Topic Document Title
IP addressing and services commands
Cisco IOS IP Command Reference, Volume 1 of 4: Addressing and Services, Release 12.3 T
IP addressing and services tasks
Cisco IOS IP Configuration Guide
No new or modified standards are supported by this feature, and support for existing standards has not been modified by this feature.
No new or modified RFCs are supported by this feature, and support for existing RFCs has not been modified by this feature.
This section documents a new command. All other commands used with this feature are documented in the Cisco IOS Release 12.3T command reference publications.
clear arp interface
To clear the entire Address Resolution Protocol (ARP) cache on an interface, use the clear arp interface command in privileged or user EXEC mode.
clear arp interface type number
No default behavior or values.
Privileged or User EXEC
This command was introduced.
This command was integrated into Cisco IOS Release 12.2(15)T.
This command was integrated into Cisco IOS Release 12.2(27)SBC.
Use the clear arp interface command to clean up ARP entries associated with an interface.
The following example clears the ARP cache from Ethernet interface 0:Router# clear arp interface ethernet 0
ARP—Address Resolution Protocol. Internet protocol used to map an IP address to a MAC address. Used to obtain the physical address when only the logical address is known.
MAC address—Media Access Control address. Standardized data link layer address that is required for every port or device that connects to a LAN. Also known as a hardware address, MAC-layer address, and physical address.
Note Refer to Internetworking Terms and Acronyms for terms not included in this glossary.
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