Intel 480T, User Manual

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C H A P T E R 6 Forwarding Database (FDB)
from becoming full with obsolete entries. Once 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 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 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 interface are stored as
permanent. The 480T switch 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 entrie s — A blackhole entry configures the switch to
discard packets with a specified MAC destination address.
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.