ZyXEL Communications ZyXEL Dimension ES-2024 - Manual (Page 145)

Dimension ES-2024 Ethernet Switch
MAC Table 23-1
Chapter 23
MAC Table
This chapter introduces the MAC Table.
23.1 Introduction to MAC Table
The MAC table 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 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 23-1 MAC Table Filtering Flowchart