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Chapter 22: Port-based and Tagged VLANs
260 Section VI: Virtual LANs
The port assignments for the VLANs are as follows:
This example is nearly identical to the “Port-based Example 2” on
page 255. Tagged ports have been added to simplify network
implementation and management.
One of the tagged ports is port 2 on the top switch. This port has been
made a tagged member of the three VLANs. It is connected to an IEEE
802.1Q-compliant server, meaning the server can handle frames from
multiple VLANs. Now all three VLANs can access the server without going
through a router or other interconnection device.
It is important to note that even though the server is accepting frames from
and transmitting frames to more than one VLAN, data separation and
security remain.
Two other tagged ports are used to simplify network design in the
example. They are port 10 on the top switch and port 9 on the lower
switch. These ports have been made tagged members of the Sales and
Engineering VLANs so that they can carry traffic from both VLANs,
simultaneously. These ports provide a common connection that enables
different parts of the same VLAN to communicate with each other while
maintaining data separation between VLANs.
In comparison, the Sales and Engineering VLANs in the “Port-based
Example 2” on page 255 each had to have its own individual network link
between the switches to connect the different parts of the VLANs. But with
tagged ports, you can use one data link to carry data traffic from several
VLANs, while still maintaining data separation and security. The tagged
frames, when received by the switch, are delivered only to those ports that
belong to the VLAN from which the tagged frame originated.
Sales VLAN (VID 2)
Engineering VLAN
(VID 3)
Production VLAN
(VID 4)
Untagged
Ports
Tagged
Ports
Untagged
Ports
Tagged
Ports
Untagged
Ports
Tagged
Ports
AT-9424T/
SP Switch
(top)
1, 3 to 5
(PVID 2)
2, 10 9, 11 to 13
(PVID 3)
2, 10 17, 19 to 21
(PVID 4)
2
AT-9424T/
GB Switch
(bottom)
2, 4, 6, 8
(PVID 2)
9 16, 18, 20,
22
(PVID 3)
9 none none