Specifications

9E312/9E423 Module Bridging
3-20 Filtering Database
destination address is located on a different network, the bridge forwards the
packet to the appropriate network. If the destination address is not found in the
Filtering Database, the bridge forwards the packet to all networks. To keep
Filtering Database entries current, older entries are purged after a period of time,
which is called the Dynamic Ageing Time.
The Filtering Database consists of two separate databases: the Static and the
Learned Databases.
The Static Database contains addresses that are entered by a network
administrator. You add these addresses directly to the database while the bridge is
powered up, or to the 9E312/9E423 Module’s battery-backed RAM so that they
are stored on shutdown till the next power-up.
The Learned Database consists of addresses that accumulate as part of the
bridge’s learning process as it is up and running. These do not remain in the
Source Address Table when the system is shut down. The Learned Database also
contains the addresses that are in the Static Database upon start-up of the bridge.
Entries to the Source Address Table are one of four types: Permanent, Static,
Dynamic, or Learned.
• Permanent entries are addresses that you add to the Static Database (via the
Filtering Database window) that are stored in the 9E312/9E423 Module’s
battery-backed RAM. Since they remain in the device on shutdown or restart,
they are considered “Permanent.”
• Static entries are addresses that you add to the Static Database (via the
Filtering Database window). These entries remain in the 9E312/9E423 Module
until it is shut down.
• Dynamic entries are addresses that you add to the Static Database (via the
Filtering Database window). With the Ageing Time feature, you set the time
period that these addresses are saved in the Source Address Table. Addresses
that have not transmitted a packet during one complete cycle of the ageing
timer are deleted from the database.
• Learned entries are addresses that are added to the Learned Database through
the bridge’s learning process. With the Ageing Time feature, you set the time
period that these addresses are saved in the Source Address Table. Addresses
which are inactive within a cycle of the ageing timer are dropped from the
database.
Learned address entries are divided into two types, Learned and Self. Address
entries classified as Learned have transmitted frames destined for a device
attached to a 9E312/9E423 Module port’s connected segment. Address entries
classified as Self are those that have sent a frame with a destination address of
one of the 9E312/9E423 Module’s bridging interfaces.
At the Filtering Database window (Figure 3-5), you can view the number of
entries of each type: Permanent, Static, Dynamic, or Learned.