Introduction To Mac Address Table - 3Com MSR 50 Series Configuration Manual

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Introduction to MAC
Address Table
MAC A
C
ONFIGURATION
n
Interfaces that MAC address table management involves can only be Layer 2
■
Ethernet interfaces.
This manual covers only static, dynamic and blackhole MAC address table
■
management. For the management of multicast MAC address table
management, refer to
page 1097.
When working with the MAC address table, go to these sections for information
you are interested in:
"Introduction to MAC Address Table" on page 2165
■
"Configuring MAC Address Table Management" on page 2166
■
"Displaying and Maintaining MAC Address Table Management" on page 2168
■
"MAC Address Table Management Configuration Example" on page 2169
■
A device maintains a MAC address table for frame forwarding. Each entry in this
table indicates the MAC address of a connected device, to which interface this
device is connected and to which VLAN the interface belongs.
A MAC address table is consists of two types of entries: static and dynamic. Static
entries are manually configured and never age out. Dynamic entries can be
manually configured or dynamically learned and may age out.
The following is how your device learns a MAC address after it receives a frame
from a port, Port 1 for example:
1 Check the frame for the source MAC address (MAC A for example).
2 Look up the MAC address table for an entry corresponding to the MAC address
and do the following:
If an entry is found for the MAC address, update the entry.
■
If no entry is found, add an entry for the MAC address and indicate from which
■
interface the frame is received.
When receiving a frame destined for MAC A, the device then looks up the MAC
address table and forwards it from port 1.
n
Dynamically learned MAC addresses cannot overwrite static MAC address entries,
but the latter can overwrite the former.
When forwarding a frame, the device adopts the following two forwarding modes
based on the MAC address table:
T
DDRESS ABLE
"Multicast Routing and Forwarding Configuration" on
M
ANAGEMENT