ZyXEL Communications IES-612-51A User Manual
IES-612-51A User’s Guide
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H A P T E R
3 8
MAC Table
This chapter introduces the MAC Table.
38.1 Introduction to MAC Table
The MAC table lists device MAC addresses that are dynamically learned by the IES-612-51A.
The table shows the following for each MAC address: the port upon which Ethernet frames
were received from the device, to which VLAN groups the device belongs (if any) and to
which channel it is connected (for devices connected to DSL ports).
The table shows the following for each MAC address: the port upon which Ethernet frames
were received from the device, to which VLAN groups the device belongs (if any) and to
which channel it is connected (for devices connected to DSL ports).
The device uses the MAC table to determine how to forward frames. See the following figure.
Figure 126 MAC Table Filtering Flowchart
1 The device examines a received frame and learns the port on which this source MAC
address came.
2 The device checks to see if the frame's destination MAC address matches a source MAC
address already learned in the MAC table.
• If the device has already learned the port for this MAC address, then it forwards the frame
to that port.
• If the device 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.