ZyXEL Communications ES-3024 Guia do Utilizador descarregar pdf (Página 158)

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

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