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1 MAC Address Table Configuration
When configuring MAC address tables, go to these sections for information you are interested in:
z Overview
z Configuring a MAC Address Table
z Displaying and Maintaining MAC Address Table
z MAC Address Table Configuration Example
Currently, interfaces involved in MAC address table configuration can only be Layer 2 Ethernet ports
and Layer 2 aggregate interfaces.
Overview
A device maintains a MAC address table for frame forwarding. Each entry in this table indicates the
MAC address of a connected device, to which interface this device is connected and to which VLAN the
interface belongs. When forwarding a frame, the device first looks up the MAC address table by the
destination MAC address of the frame for the outgoing port. If the outgoing port is found, the frame is
forwarded rather than broadcast. Thus, broadcasts are reduced.
How a MAC Address Table Entry Is Created
A MAC address table entry can be dynamically learned or manually configured.
Dynamically learning MAC address entries
Usually, a device can populate its MAC address table automatically by learning the source MAC
addresses of received frames.
The following is how a device learns a MAC address when it receives a frame from a port, Port A for
example:
1) Check the source MAC address (MAC-SOURCE for example) of the frame. Assume that frames
with the source MAC address MAC-SOURCE can be forwarded through Port A.
2) Look up the MAC address table by the MAC address for a match and do the following:
z If an entry is found for the MAC address, update the entry.
z If no entry is found, add an entry for the MAC address to indicate from which port the frame is
received.
When receiving a frame destined for MAC-SOURCE, the device looks up the MAC address table and
forwards it from Port A.
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