Specifications

ExtremeWare XOS 11.0 Concepts Guide 103
7 Forwarding Database
This chapter describes the following topics:
• Overview of the FDB on page 103
• MAC-Based Security on page 106
• Displaying FDB Entries on page 106
Overview of the FDB
The switch maintains a database of all MAC addresses received on all of its ports. It uses the
information in this database to decide whether a frame should be forwarded or filtered.
FDB Contents
Each Fowarading Database (FDB) entry consists of the MAC address of the device, an identifier for the
port and VLAN on which it was received, and the age of the entry. Frames destined for MAC addresses
that are not in the FDB are flooded to all members of the VLAN.
How FDB Entries Get Added
Entries are added into the FDB in the following ways:
• The switch can learn entries by examining packets it receives. The system updates its FDB with the
source MAC address from a packet, the VLAN, and the port identifier on which the source packet is
received.
The ability to learn MAC addresses can be enabled or disabled on a port-by-port basis.
NOTE
For more information on port control for learning MAC address, refer to Chapter 4.
• You can enter and update entries using the command line interface (CLI).
• Certain static entries are added by the system upon switch boot-up.