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Catalyst 2950 and Catalyst 2955 Switch Software Configuration Guide
OL-10101-02
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 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, see the Cisco IOS Release documentation on Cisco.com.
Ta b l e 7-4 Commands for Displaying the MAC Address Table
Command Description
show mac address-table address Displays MAC address table information for the specified MAC address.
show mac address-table aging-time Displays the aging time in all VLANs or the specified VLAN.
show mac address-table count Displays the number of addresses present in all VLANs or the specified VLAN.
show mac address-table dynamic Displays dynamic MAC address table entries only.
show mac address-table interface Displays the MAC address table information for the specified interface.
show mac address-table multicast Displays the Layer 2 multicast entries for all VLANs or the specified VLAN.
show mac address-table static Displays static MAC address table entries only.
show mac address-table vlan Displays the MAC address table information for the specified VLAN.