User guide

5-2 B

LACK

IAMOND

SER

UIDE

ORWARDING

ATABASE

(FDB)

BlackDiamond is reset or a power off/on cycle occurs. For more information about

setting the aging time, refer to the section “Configuring FDB Entries,” later in this

chapter.

• Non-aging entries — If the aging time is set to zero, all aging entries in the database

are defined as static, non-aging 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

BlackDiamond 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 interface

are stored as permanent. The BlackDiamond can support a maximum of 64

permanent entries.

Once created, permanent entries stay the same as when they were created. For

example. the permanent entry store is not updated when any of the following take

place:

— A VLAN is deleted.

— A VLANid is changed.

— A port mode is changed (tagged/untagged).

— A port is deleted from a VLAN.

— A port is disabled.

— A port enters blocking state.

— A port QoS setting is changed.

— A port goes down (link down).

• Blackhole entries — A blackhole entry configures packets with a specified MAC

destination address to be discarded. Blackhole entries are useful as a security

measure or in special circumstances where a specific destination address must be

discarded. Blackhole entries are treated like permanent entries in the event of a

switch reset or power off/on cycle. Blackhole entries are never aged out of the

database.