how to set dynamic mac address learning in cisco

#How to set dynamic mac address learning in cisco how to

The maximum size of the MAC address table varies with different switches. To create a static mapping in the MAC address table, use the mac-address-table static vlan interfaceinterface-id command. Only those devices that are known to the network administrator can connect to the network. One reason to implement static MAC addresses is to provide the network administrator complete control over access to the network. As a result, there is no need to relearn or refresh which port the MAC address is connected to. Static addresses are not aged out, and the switch always knows which port to send out traffic destined for that specific MAC address. As computers are added or removed from the network, the switch updates the MAC address table, adding new entries and aging out those that are currently not in use.Ī network administrator can specifically assign static MAC addresses to certain ports. The switch provides dynamic addressing by learning the source MAC address of each frame that it receives on each port, and then adding the source MAC address and its associated port number to the MAC address table. Setting too long an aging time can cause the address table to be filled with unused addresses, which prevents new addresses from being learned. This unnecessary flooding can impact performance. Then, when the switch receives a packet for an unknown destination, it floods the packet to all ports in the same LAN (or VLAN) as the receiving port. Setting too short an aging time can cause addresses to be prematurely removed from the table. You can change the aging time setting for MAC addresses. Note: The MAC address table was previously referred to as content addressable memory (CAM) or as the CAM table.ĭynamic addresses are source MAC addresses that the switch learns and then ages when they are not in use. The figure shows a sample MAC address table from the output of the show mac-address-table command that includes static and dynamic MAC addresses. These MAC tables include dynamic and static addresses.

#How to set dynamic mac address learning in cisco how to

Switches use MAC address tables to determine how to forward traffic between ports.