LAN9117_08 Datasheet, PDF (25/136 Pages) SMSC Corporation – High Performance Single-Chip 10/100 Non-PCI Ethernet Controller

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
CCC
DDD
VLAN 2
EEE
AAA
BBB
LAN Switch #1
VLAN 1
FFF
GGG
HHH
LAN Switch #2
VLAN Config Data
Address
AAA
BBB
CCC
DDD
EEE
FFF
GGG
HHH
VLAN #
VLAN 3
VLAN 3
VLAN 3
VLAN 2
VLAN 2
VLAN 2
VLAN 1
VLAN 1
LAN Switch #3
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".
SMSC LAN9117
25
DATASHEET
Revision 1.5 (07-11-08)