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Overview of Installation and Configuration
How to Configure VLANs on the Switch
Chapter 2 23
How to Configure VLANs on the Switch
IEEE 802.1Q compliant devices and legacy/untagged VLANs can coexist
on the same networks, but legacy/untagged VLANS require a separate
link, whereas the 802.1Q tagged VLANs can combine several VLANs
into one link. On 802.1Q-compliant devices, separate ports (configured as
untagged) must be used to connect separate VLANs to non-802.1Q
devices.
Figure 2-2 Tagged and Untagged VLAN Technology in Same Network
When you assign a switch port to a given VLAN, you must implement the
VLAN tag if the switch port will carry traffic for more than one VLAN.
Otherwise, the port VLAN assignment can remain untagged because
the tag is not needed. On a given switch, use the untagged designation
for a port VLAN assignment where the port is connected to a
non-802.1Q-compliant device or is assigned to only one VLAN as in
VLAN 1 in Figure 2-2. Use the tagged designation when more than one
VLAN is assigned to the port, or the port is connected to a device that
does comply with the 802.1Q standard as in VLANs 2 through 4 in
Figure 2-2. These simple rules are summarized in Table 2-1.
Untagged
Switch Port
LAN
Card
Tagged
VLAN 1
VLAN 2
VLAN 3
VLAN 4
untagged or native VLAN
tagged VLAN
tagged VLAN
tagged VLAN
Port