Zyxel OLT2412 [253/326] Mac table

OLT2412 User’s Guide 253

CHAPTER 35

MAC Table

This chapter introduces the MAC address commands.

35.1 MAC Table Overview

The MAC table (a MAC table is also known as a filtering database) shows how frames are forwarded

or filtered across the OLT’s ports. When a device (which may belong to a VLAN group) sends a

packet which is forwarded to a port on the OLT, the MAC address of the device is shown on the

OLT’s MAC table. It also shows whether the MAC address is dynamic (learned by the OLT) or static

(manually entered by static MAC forwarding).

The OLT uses the MAC table to determine how to forward frames. See the following figure.

1 The OLT examines a received frame and learns the port from which this source MAC address came.

2 The OLT checks to see if the frame's destination MAC address matches a source MAC address

already learned in the MAC table.

• If the OLT has already learned the port for this MAC address, then it forwards the frame to that

port.

• If the OLT 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 OLT 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 62 MAC Table Flowchart