Chapter 52 MAC Table
GS2220 Series User’s Guide
439
C HAPTER 52
MAC Ta ble
52.1 MAC Ta ble O ve rvie w
This chapter introduces the MAC Ta ble screen.
The MAC Ta b le 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 ports and whether the MAC address is dynamic (learned by
the Switch) or static (manually entered in the Sta tic MAC Fo rwa rding screen).
52.1.1 Wha t You C a n Do
Use the MAC Ta ble screen (
Section 52.2 on page 440) to check whether the MAC address is dynamic or
static.
52.1.2 Wha t You Ne e d to Kno w
The Switch uses the MAC Ta ble 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 Ta ble .
• 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, then the Switch sends an ARP to request
the MAC address. The Switch then learns the port that replies with the MAC address.
• 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.
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