Static Virtual LANs (VLANs)
802.1Q VLAN Tagging
VLAN tagging enables traffic from more than one VLAN to use the same port. (Even when two or more VLANs use the same port they remain as separate domains and cannot receive traffic from each other without going through an external router.) As mentioned earlier, a “tag” is simply a unique VLAN identification number (VLAN ID, or VID) assigned to a VLAN at the time that you configure the VLAN name in the switch. The tag can be any number from 1 to 4094 that is not already assigned to a VLAN. When you subsequently assign a port to a given VLAN, you must implement the VLAN tag (VID) if the 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, this means you should use the “Untagged” designation for a port VLAN assignment where the port is connected to non
For example, if port A7 on an
| Blue |
| Blue | White | White | ||
| Server | VLAN | Server | VLAN | |||
Red | 5 | 6 | Red VLAN: Untagged | 4 | 3 | ||
VLAN | |||||||
4 |
| Green VLAN: Tagged |
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| Switch | Switch | |||||
| 7 | 5 | |||||
| 3 | "X" |
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| "Y" | |
Red |
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2 | 1 |
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| 1 | 2 | ||
Server |
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| Green | Green | Red |
| Green | ||
| Server | VLAN | VLAN | VLAN | |||
| Ports | Ports | |||||
| Port 7: Red VLAN Untagged | Port 5: Red VLAN Untagged | |||||
| Green VLAN Tagged | Green VLAN Tagged |