Example 2 - Cabletron Systems DLE52-MA User Manual

Chapter 4: Examples
3. Once the frame is classified, its destination MAC address is examined.
The switch discovers that the frame is a broadcast, and treats it as it
would any other unknown destination MAC address. The switch
forwards the frame out all ports in the Red VLAN's Forwarding List
except for the one that received the frame. In this case, the frame is
sent to Ports 2 and 3.
The second frame is a unicast, where station R2 responds to station
R1's broadcast.
4. Station R2, having received and recognized the broadcast from R1,
transmits a unicast frame as a response. The switch receives this frame
on Port 2. The switch classifies this new untagged frame as belonging
to the Red VLAN.
5. The switch adds the source MAC address and VLAN for station R2 to
its Source Address Table in FID 2, and checks the Source Address
Table for the destination MAC address given in the frame. The switch
finds the MAC address and VLAN in this table, and recognizes that
the MAC address and VLAN match for R1 is located out Port 1.
6. The switch examines its VLAN configuration information and
determines that the frame for Red VLAN is allowed to be forwarded
out Port 1 and that it must be sent in an untagged format.
7. The switch forwards the frame out Port 1. Any other unicast
transmissions between stations R1 and R2 will be handled identically.
4.2

EXAMPLE 2

This second example investigates the steps that must be taken to set up
VLANs across multiple 802.1Q VLAN switches. This includes the
configuration and operation of 1Q Trunks between 802.1Q VLAN
switches.
As shown in Figure 4-3, two companies, "Redco" and "Blue Industries",
share floors 2 and 4 in a building where the network infrastructure is
supplied by the building owner. The objective is to completely isolate the
network traffic of the two companies by limiting the user's traffic through
the ports of two switches, thus maintaining security and shielding the
network traffic from each company. This example will show the use and
configuration of a 1Q Trunk connection and the creation of VLANs across
multiple switches.
4-4 802.1Q VLAN User's Guide