Configuring The Mac Address Table; Information About Mac Addresses - Cisco Nexus 5000 Series Configuration Manual

Configuring the MAC Address Table

All Ethernet interfaces on Cisco Nexus 5000 Series switches maintain media access control (MAC) address
tables. This chapter describes the configuration of the MAC address tables. It includes the following sections:
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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.
Information About MAC Addresses, page 221
Configuring MAC Addresses, page 222
Verifying the MAC Address Configuration, page 223
Cisco Nexus 5000 Series NX-OS Layer 2 Switching Configuration Guide, Release 5.0(3)N1(1)
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