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N
P
ETWORK
LANNING
Making VLAN Connections
VLANs can be based on port groups, or each data frame can be
explicitly tagged to identify the VLAN group it belongs to. When
using port-based VLANs, ports can either be assigned to one
specific group or to all groups. Port-based VLANs are suitable for
small networks. A single switch can be easily configured to
support several VLAN groups for various organizational entities
(such as Finance and Marketing).
When you expand port-based VLANs across several switches, you
need to make a separate connection for each VLAN group. This
approach is, however, inconsistent with the Spanning Tree
Protocol, which can easily segregate ports that belong to the same
VLAN. When VLANs cross separate switches, it is therefore better
to use VLAN tagging. This allows you to assign multiple VLAN
groups to the "trunk" ports (that is, tagged ports) connecting
different switches.
R&D
VLAN 1
VLAN 2
Testing
Figure 2-3. Making VLAN Connections
Note: When connecting to a switch that does not support IEEE
802.1Q VLAN tags, use untagged ports.
2-4
1
2
3
4
5
Tagged
13
14
15
17
16
Ports
Untagged Ports
Finance
Marketing
VLAN 3
VLAN 4
6
7
8
9
10
11
12
1
2
3
4
5
6
7
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11
Link
Status
Link
Status
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Tagged Port
VLAN
unaware
switch
Finance
VLAN 3
12
M1
Tiger Switch 10/100
COL
Power
6724L2
ACT
FDX
SNMP
100M
Console
Status
24
M2
R&D
VLAN 1
VLAN 2
VLAN
aware
switch
Testing
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