Mac Address Table Management Configuration; Introduction To Mac Address Table - 3Com Switch 4800G 24-Port Configuration Manual

20
Introduction to MAC
Address Table
MAC A
C
ONFIGURATION
When configuring MAC address table management, go to these sections for
information you are interested in:
"Introduction to MAC Address Table" on page 173
■
"Configuring MAC Address Table Management" on page 174
■
"Displaying and Maintaining MAC Address Table Management" on page 176
■
"MAC Address Table Management Configuration Example" on page 176
■
n
This manual covers only static, dynamic and blackhole MAC address table
management. For the management of multicast MAC address table management,
refer to "Multicast Routing and Forwarding Configuration" on page 701.
A switch maintains a MAC address table for frame forwarding. Each entry in this
table contains the MAC address of a connected device, to which port this device is
connected and to which VLAN the port belongs.
A MAC address table 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 a switch learns a MAC address after it receives a frame from
a port, port A for example:
1 Check the frame for the source MAC address (MAC-SOURCE for example), and
consider frames with destination MAC address MAC-SOURCE be forwarded
through port A.
2 Look up the MAC address table for an entry corresponding to the MAC address
and do the following:
3 If an entry is found for the MAC address, update the entry.
4 If no entry is found, add an entry containing the MAC address and port A.
When receiving a frame destined for MAC A, the switch then looks up the MAC
address table and forwards it from port A.
n
Dynamically learned MAC addresses cannot overwrite static MAC address entries,
but the latter can overwrite the former.
T
DDRESS ABLE
M
ANAGEMENT