Static Virtual LANs (VLANs)
VLAN tagging gives you several options:
■Since the purpose of VLAN tagging is to allow multiple VLANs on the same port, any port that has only one VLAN assigned to it can be configured as “Untagged” (the default).
■Any port that has two or more VLANs assigned to it can have one VLAN assignment for that port as “Untagged”. All other VLANs assigned to the same port must be configured as “Tagged”. (There can be no more than one Untagged VLAN on a port.)
■If all end nodes on a port comply with the 802.1Q standard and are configured to use the correct VID, then, you can configure all VLAN assignments on a port as “Tagged” if doing so makes it easier to manage your VLAN assignments, or for security reasons.
For example, in the following network, switches X and Y and servers S1 and S2 are
Server | Server |
|
| |||
S1 |
|
| S2 |
|
| |
Red VLAN: Untagged |
|
| Red VLAN: Untagged |
| ||
Green VLAN: Tagged |
|
| Green VLAN: Tagged |
| ||
X1 | Red VLAN: Untagged |
| Y1 |
|
|
|
| Green VLAN: Tagged |
|
|
| Green VLAN only | Server |
Switch X2 | Y5 | Switch Y2 | ||||
"X" |
|
| "Y" |
| S3 | |
X4 | X3 |
| Y4 | Y3 |
| |
Red | Green | Red |
| Green |
| |
VLAN | VLAN | VLAN |
| VLAN |
|
Figure