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C H A P T E R 7 Virtual LANs (VLANs)
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• On System 2, ports 1 through 4 are part of VLAN Accounting
and ports 5 through 8, 15, and 16 are part of VLAN Engineering.
Figure 7.3: Two port-based VLANs spanning two switches
• VLAN
Accounting spans System 1 and System 2 by way of a
connection between System 1, port 12 and System 2, port 1.
• VLAN
Engineering spans System 1 and System 2 by way of a
connection between System 1, port 13, and System 2, port 16.
Using this configuration, you can create multiple VLANs that span
multiple switches, in a daisy-chained fashion. To function properly:
• Each switch must have a dedicated port for each VLAN.
• Each dedicated port must be connected to a port that is a member
of its VLAN on the next switch.
Tagged VLANs
Tagging is a process that inserts a marker (called a tag) into the
Ethernet frame. The tag includes the identification number of a
specific VLAN, called the VLANid.
Using 802.1Q tagged packets may create packets slightly bigger
than the current IEEE 802.3/Ethernet maximum of 1,518 bytes.
This may affect packet error counters in other devices, and may also
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3421
7865
11 12109
13 161514
3421
7865
11 12109
13 161514
Accounting Engineering
System 1
System 2
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