Cisco Systems N3KC3064TFAL3 Configuring the MAC Address Table, Information About MAC Addresses

C H A P T E R 12

Configuring the MAC Address Table

This chapter contains the following sections:

•Information About MAC Addresses, page 131

•Configuring MAC Addresses, page 131

•Verifying the MAC Address Configuration, page 133

Information About MAC Addresses

To switch frames between LAN ports, the switch maintains an address table. When the switch receives a frame, it associates the media access control (MAcC) address of the sending network device with the LAN port on which it was received.

The switch dynamically builds the address table by using the MAC source address of the frames received. When the switch receives a frame for a MAC destination address not listed in its address table, it floods the frame to all LAN ports of the same VLAN except the port that received the frame. When the destination station replies, the switch adds its relevant MAC source address and port ID to the address table. The switch then forwards subsequent frames to a single LAN port without flooding all LAN ports.

You can also enter a MAC address, which is termed a static MAC address, into the table. These static MAC entries are retained across a reboot of the switch.

In addition, you can enter a multicast address as a statically configured MAC address. A multicast address can accept more than one interface as its destination.

The address table can store a number of unicast and multicast address entries without flooding any frames. The switch uses an aging mechanism, defined by a configurable aging timer, so if an address remains inactive for a specified number of seconds, it is removed from the address table.

Configuring MAC Addresses

Configuring a Static MAC Address

You can configure MAC addresses for the switch. These addresses are static MAC addresses.

Cisco Nexus 3000 NX-OS Layer 2 Switching Configuration Guide, Release 5.0(3)U3(1)

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