Static Virtual LANs (VLANs)

802.1Q VLAN Tagging

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VLAN

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VLAN

 

 

 

 

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VLAN

 

 

 

 

 

 

 

 

 

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Switch

 

Green VLAN: Tagged

 

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Switch

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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“Y”

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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Green

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Server

VLAN

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Ports 1 - 4: Untagged

Ports 1 - 6: Untagged

Port 7: Red VLAN Untagged

Port 5: Red VLAN Untagged

Green VLAN Tagged

Green VLAN Tagged

Figure 2-26. Example of Tagged and Untagged VLAN Port Assignments

In switch X:

VLANs assigned to ports X1 - X6 can all be untagged because there is only one VLAN assignment per port. Red VLAN traffic will go out only the Red ports; Green VLAN traffic will go out only the Green ports, and so on. Devices connected to these ports do not have to be 802.1Q- compliant.

However, because both the Red VLAN and the Green VLAN are assigned to port X7, at least one of the VLANs must be tagged for this port.

In switch Y:

VLANs assigned to ports Y1 - Y4 can all be untagged because there is only one VLAN assignment per port. Devices connected to these ports do not have to be 802.1Q-compliant.

Because both the Red VLAN and the Green VLAN are assigned to port Y5, at least one of the VLANs must be tagged for this port.

In both switches: The ports on the link between the two switches must be configured the same. As shown in figure 2-26(above), the Red VLAN must be untagged on port X7 and Y5 and the Green VLAN must be tagged on port X7 and Y5, or vice-versa.

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