ZyXEL Communications XGS2220 Series, Руководство пользователя

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Chapter 12 MAC Table
XGS2220 Series User’s Guide
129
C
HAPTER
12
MAC Table
12.1 MAC Table Overview
This chapter introduces the MAC Table screen.
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. 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
SWITCHING > Static MAC Forwarding screen).
12.1.1 What You Can Do
Use the MAC Table screen ( Section 12.2 on page 130 ) to check whether the MAC address is dynamic or
static.
12.1.2 What You Need to Know
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, 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.