This figure shows the difference between using three untagged interfaces (where each interface
must belong to a separate VLAN) versus one single-tagged interface (which belongs to multiple
The configuration on the left shows a BIG-IP system with three internal interfaces, each a separate, untagged interface. This is a typical solution for supporting three separate customer sites. In this scenario, each interface can accept traffic only from its own VLAN.
Conversely, the configuration on the right shows a BIG-IP system with one internal interface
and an external switch. The switch places the internal interface on three separate VLANs. The
interface is configured on each VLAN as a single-tagged interface. In this way, the single
interface becomes a tagged member of all three VLANs, and accepts traffic from all three. The
configuration on the right is the functional equivalent of the configuration of the left.
If you are connecting another switch into a BIG-IP system interface, the VLAN tag that you assign to the VLAN on the BIG-IP system must match the VLAN tag on the interface of the other switch.