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4-16 C
HAPTER
4: M
ANAGING
T
HE
S
WITCH
1000
Setting Up the Switch Database (SDB)
The Switch maintains a database of device addresses
that it receives on its ports. It uses the information
in this database to decide whether a frame should
be forwarded or filtered. The database holds up to a
maximum of 500 entries; each entry consists of the
MAC address of the device and an identifier for the
port on which it was received.
If you have set up Traps for the Switch, notification
that the database is becoming full is provided by
two traps:
■
Database is 90% full
■
Database is 100% full
These traps indicate that the maximum number of
devices which can be connected to the Switch has
been reached. You cannot connect any more devices
to the Switch. Additional devices can, however, be
connected to the rest of the network.
Entries are added into the Switch Database in two
ways:
■
The Switch can learn entries. That is, the unit
updates the SDB with the source MAC address,
and the port identifier on which the source MAC
address is seen. Addresses are not learned on
the backbone port. Learning is affected by secu-
rity (refer to the description for the Security field
on page 4-13
).
■
The system administrator can enter and update
entries using a MIB browser, an SNMP Network
Manager or the Switch Database screen
described in the following sections.
There are three types of entries in the SDB:
■
Ageing entries
— Initially, all entries in the data-
base are ageing entries. Entries in the database
are removed (aged out) if, after a period of time
(ageing 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. Ageing entries are
deleted from the database if the Switch is reset
or a power-off/on cycle occurs. For more informa-
tion about setting an ageing time, refer to “
Set-
ting Up the Switch Unit” on page 4-9.
■
Non-ageing entries
— If the ageing time is set
to 0:00, all ageing entries in the database are
defined as non-ageing entries. This means that
they do not age, but they are still deleted if the
Switch is reset or a power off/on cycle occurs. For
more information about setting an ageing time,
refer to “
Setting Up the Switch Unit” on page
4-9.
■
Permanent entries
— Permanent entries do
not age, and they are retained in the database if
the Switch is reset or a power-off/on cycle occurs.