Displaying Address Table Entries; Managing The Arp Table - Cisco 2950 - Catalyst Switch Configuration Manual

Managing the ARP Table

Command
Step 4 show mac address-table static
Step 5
copy running-config startup-config
To disable unicast MAC address filtering, use the no mac address-table static mac-addr vlan vlan-id
global configuration command.
This example shows how to enable unicast MAC address filtering and to configure the switch to drop
packets that have a source or destination address of c2f3.220a.12f4. When a packet is received in
VLAN 4 with this MAC address as its source or destination, the packet is dropped:
Switch(config)# mac address-table static c2f3.220a.12f4 vlan 4 drop

Displaying Address Table Entries

You can display the MAC address table by using one or more of the privileged EXEC commands
described in
Table 8-4 Commands for Displaying the MAC Address Table
Command
show mac address-table address
show mac address-table aging-time
show mac address-table count
show mac address-table dynamic
show mac address-table interface
show mac address-table multicast
show mac address-table static
show mac address-table vlan
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 12.1 documentation on Cisco.com.
Catalyst 2950 and Catalyst 2955 Switch Software Configuration Guide
8-28
Purpose
Verify your entries.
(Optional) Save your entries in the configuration file.
Table 8-4:
Description
Displays MAC address table information for the specified MAC address.
Displays the aging time in all VLANs or the specified VLAN.
Displays the number of addresses present in all VLANs or the specified VLAN.
Displays dynamic MAC address table entries only.
Displays the MAC address table information for the specified interface.
Displays the Layer 2 multicast entries for all VLANs or the specified VLAN.
Displays static MAC address table entries only.
Displays the MAC address table information for the specified VLAN.
Chapter 8 Administering the Switch
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