3Com TR - Manual (Page 77)

About the Switch Database (SDB) 4-19
About the Switch Database (SDB)
The Switch 2000 TR supports a database of transpar-
ent addresses received on its local ports. Using this
information, the Switch 2000 TR determines whether
a transparent frame should be forwarded or filtered.
The database holds a maximum of 2000 entries, each
of which includes the MAC address and an identifier
for the port on which it was received.
The Switch 2000 TR Unit Database View allows you
to set up, maintain, and view the Switch 2000 TR
database.
SNMP Traps report the database status as follows:
■ Database 90% full
■ Database 100% full
These traps indicate that the maximum number of users
has been or is about to be met. When the maximum
number has been met, you cannot add any more users to
the database until some are removed. This limitation does
not apply to users connected to the remainder of the net-
work.
Database Entries
The Switch 2000 TR database has two types of
entries:
■ Aging Entries—Initially, all entries in the database
are the aging type. As traffic moves through the
Switch 2000 TR, device addresses are learned and
stored. Entries are removed (aged out) if the device
has not transmitted any packets for a set period of
time (aging time). This practice prevents the data-
base from filling with obsolete entries. When a
device is removed from the network, its entry is
deleted from the database. Using an SNMP-based
management application or the VT100 console
(serial port or Telnet session), you can set the aging
time (set in seconds) with a default of 5 minutes.
Aging entries are deleted if the Switch 2000 TR is
reset or turned off.
■ Permanent Entries—Permanent entries are
retained in the database even when the Switch
2000 TR is reset or powered down. Addresses are
made permanent by a system administrator via a
network manager application and the switch data-
base. Refer to “Switch Database Configuration”
for more information.
Database Entry Methods
Entries to the database happen in two ways:
■ The Switch 2000 TR can learn up to 2000
addresses. Addresses include the source MAC
address and the port identifier of the port on
which the source MAC address is seen. Addresses
are not learned on the designated downlink.
■
The system administrator can enter and update
entries using an SNMP MIB browser, a network
manager application, or the Switch 2000 TR data-
base screen. Refer to “Switch Database Configura-
tion” for more information.