VLANs are a layer 2 concept. We can all agree on that but why, then, do we use the 'interface vlanX' to allow routing on a switch. If we want to setup a default gateway for VLAN X on a Layer 3 switch would be be able to accomplish the same goal with an 'interface loopbackX' command as an 'interface vlanX' command? Aren't they both just virtual interfaces that can be used to hold IP addresses and thus route?