Cabletron Systems 802.1Q VLAN User Manual page 14

Chapter 1: Virtual Local Area Networks
Building One Building Two
S S S S S S
F F F F
10
9
8
trunk 7
1 6
A B
SmartSwitch SmartSwitch
S F
Member of Sales Network
Member of Finance Network
2263-01
Figure 1-1 Example of a VLAN
In this example, the Sales and Finance workstations have been placed on
two separate VLANs. In a plain Ethernet environment, the entire network
is a broadcast domain, and the SmartSwitches follow the IEEE 802.1D
bridging specification to send data between stations. A broadcast or
multicast transmission from a Sales workstation in Building One would
propagate to all the switch ports on SmartSwitch A, cross the high speed
link to SmartSwitch B, and then propagated out all switch ports on
SmartSwitch B. The SmartSwitches treat each port as being equivalent to
any other port, and have no understanding of the departmental
memberships of each workstation.
In a VLAN environment, each SmartSwitch understands that certain
individual ports or frames are members of separate workgroups. In this
environment, a broadcast or multicast data transmission from one of the
Sales stations in Building One would reach SmartSwitch A, be sent to the
ports connected to other local members of the Sales VLAN, cross the high
speed link to SmartSwitch B, and then be sent to any other ports and
workstations on SmartSwitch B that are members of the Sales VLAN.
1-2 802.1Q VLAN User's Guide