ZyXEL Communications Dimension ES-3024, User Manual, Page: 158 / 212

Dimension ES-3024 Ethernet Switch
Filtering Database 23-1
Chapter 23
Filtering Database
This chapter introduces Filtering Database.
23.1 Introduction to Filtering Database
The Filtering Database shows how frames are forwarded or filtered across the switch’s ports. It shows what device
MAC address, belonging to what VLAN group (if any) is forwarded to which port(s) and whether the MAC address
is dynamic (learned by the switch) or static (manually entered in
Static MAC Forwarding ).
The switch uses the Filtering Database to determine how to forward frames. See the following figure.
1. The switch examines a received frame and learns the port on which this source MAC address came.
2. The switch checks to see if the frame's destination MAC address matches a source MAC address already
learned in the Filtering Database.
If the switch has already learned the port for this MAC address, then it forwards the frame to that port.
If the switch has not already learned the port for this MAC address, then the frame is flooded to all
ports. Too much port flooding leads to network congestion.
If the switch has already learned the port for this MAC address, but the destination port is the same as
the port it came in on, then it filters the frame.
Figure 23-1 Filtering Database Flowchart