Cisco Systems 3750E manual Managing the ARP Table, Displaying Address Table Entries

Chapter 7 Administering the Switch

Managing the ARP Table

Displaying Address Table Entries

You can display the MAC address table by using one or more of the privileged EXEC commands described in Table 7-4:

Table 7-4	Commands for Displaying the MAC Address Table
Command		Description
show ip igmp snooping groups		Displays the Layer 2 multicast entries for all VLANs or the specified VLAN.
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 only dynamic MAC address table entries.
show mac address-table interface		Displays the MAC address table information for the specified interface.
show mac address-table notification		Displays the MAC notification parameters and history table.
show mac address-table static		Displays only static MAC address table entries.
show mac address-table vlan		Displays the MAC address table information for the specified VLAN.

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.

Catalyst 3750-E and 3560-E Switch Software Configuration Guide

OL-9775-02 7-27