LAN9115_05 Datasheet, PDF (24/131 Pages) SMSC Corporation – Highly Efficient Single- Chip 10/100 Non-PCI Ethernet Controller

Highly Efficient 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".
Revision 1.1 (05-17-05)
24
DATASHEET
SMSC LAN9115