ZyXEL Communications ES-2048, User Manual

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ES-2048 User’s Guide
253
C
H A P T E R
31
MAC Table
This chapter introduces the MAC Table screen.
31.1 MAC Table Overview
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 149 MAC Table Flowchart