VLANs are identified by a four-byte tag that is inserted at the front of the Layer 2 Ethernet header. Having this additional tag means that interfaces configured for 802.1Q are not compatible with standard Ethernet packets. When considering whether or not to use a VLAN interface, keep the following in mind.

• If you are using 802.1Q VLANs, create vif configuration nodes beneath the physical interface and assign the IP address to the vif.
• If you are not using 802.1Q but want to have multiple networks on the same physical interface (that is, you want to use multinetting but not VLANs), simply create multiple address configuration nodes directly under the physical interface without using vifs.