ZyXEL Communications GS1920-48HPv2, Руководство пользователя

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Chapter 45 MAC Table
GS1920v2 Series User’s Guide
381
C
HA PTER
4 5
MAC Ta b le
45.1 MAC Ta b le O ve rvie w
This chapter introduces the
MAC Ta b le
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 port(s) and whether the MAC address is dynamic (learned by
the Switch) or static (manually entered in the
Sta tic MAC Fo rwa rding
screen).
45.1.1 Wha t Yo u C a n Do
Use the
MAC Ta b le
screen ( Section 45.2 on page 382 ) to check whether the MAC address is dynamic or
static.
45.1.2 Wha t Yo u Ne e d to Kno w
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.