ZyXEL ES-3148 Guida Utente

ES-3148 User’s Guide

This chapter introduces the MAC Table screen.

The MAC Table screen (a MAC table is also known as a 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 the Static MAC 
Forwarding screen).
The Switch uses the MAC table 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 MAC table. 

• 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 160   MAC Table Flowchart