High Performance Single-Chip 10/100 Non-PCI Ethernet Controller
Datasheet
Network efficiency: Allows shielding one system resource from traffic not meant for that resource. A
workstation in one VLAN is shielded from traffic on another VLAN, increasing that workstation’s
efficiency.
Broadcast containment: Leakage of broadcast frames from one VLAN to another is prevented.
VLAN 3
VLAN 2
CCC
DDD
EEE
AAA
BBB
VLAN 1
FFF
GGG
HHH
LAN Switch #1
LAN Switch #2
VLAN Config Data
LAN Switch #3
Address
VLAN #
AAA
BBB
CCC
DDD
EEE
FFF
VLAN 3
VLAN 3
VLAN 3
VLAN 2
VLAN 2
VLAN 2
VLAN 1
VLAN 1
GGG
HHH
Figure 3.1 VLAN Topology
When the members of a VLAN are not located on the same physical medium, the VLAN uses a tag
to help it determine how to forward the frame from one member to another. The tag structure was
proprietary until the IEEE released a supplement to 802.3 defining the VLAN frame structure, including
the tag. This new frame structure for VLAN is depicted in Figure 3.2, "VLAN Frame".
Revision 1.1 (05-17-05)
SMSC LAN9117
DATA2S4HEET
SMSC [ SMSC CORPORATION ]
