How do I divide a network into smaller subnets using a single Layer 3 switch?

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http://serverfault.com – I have had trouble searching for help on this one, as most searches for VLSM, CIDR and layer 3 switching bring back very basic questions posted by students just starting their CCNA. I have a batch of public IPs that have been assigned to me. These come in on the end of an Ethernet cable out of the ISP's router. To keep things simple let's say that my ISP has given me a full (hypothetical address). I would like to split that up into multiple distinct /28 networks. I have a layer 3 switch. Here's what I have tried: I created three vlans on the switch. I created three interfaces (HowTos)