Overview Of The Fdb; Fdb Contents; Fdb Entry Types - Extreme Networks 200 Series Installation And User Manual

8
Forwarding Database (FDB)
This chapter describes the following topics:
• Overview of the FDB on page 109
• Configuring FDB Entries on page 111
• Displaying FDB Entries on page 112

Overview of the FDB

The switch maintains a database of all media access control (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 FDB entry consists of the MAC address of the device, an identifier for the port on which it was
received, and an identifier for the VLAN to which the device belongs. Frames destined for devices that
are not in the FDB are flooded to all members of the VLAN.

FDB Entry Types

The Summit 200 series switch supports up to 8,191 layer 2 FDB entries and 2,047 layer 3 FDB entries.
The following are four types of entries in the FDB:
• Dynamic entries—Initially, all entries in the database are dynamic. Entries in the database are
removed (aged-out) if, after a period of time (aging time), the device has not transmitted. This
prevents the database from becoming full with obsolete entries by ensuring that when a device is
removed from the network, its entry is deleted from the database. Dynamic entries are deleted from
the database if the switch is reset or a power off/on cycle occurs. For more information about setting
the aging time, refer to "Configuring FDB Entries" later in this chapter.
• Nonaging entries—If the aging time is set to zero, all aging entries in the database are defined as
static, nonaging entries. This means that they do not age, but they are still deleted if the switch is
reset.
• Permanent entries—Permanent entries are retained in the database if the switch is reset or a power
off/on cycle occurs. The system administrator must make entries permanent. A permanent entry can
either be a unicast or multicast MAC address. All entries entered by way of the command-line
Summit 200 Series Switch Installation and User Guide 109