ZyXEL Communications XGS4700 Series, Manual

Page: 435 / 485

XGS4700-48F User’s Guide
435
C
H A P T E R
4 9
MAC Table
This chapter introduces the MAC Table screen.
49.1 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. When a device
(which may belong to a VLAN group) sends a packet which is forwarded to a port
on the Switch, the MAC address of the device is shown on the Switch’s MAC
Table. It also shows 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 from 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.