Amazon Virtual Private Cloud
The book I read to research this post was the Amazon VPC User guide which is an excellent book which I downloaded for free from kindle. Amazon VPC integrates with Elastic Compute Cloud EC2 and allows you to set up a virtual network. You can simply run something like a blog on it or have a complex network with a website, database server not connected directly to the internet and several workstations all connected to the web. It allows you to reserve IP addresses for your hardware, although you can only have 5 networks per account and only 20 computers set up per network. There's nothing stopping you setting up more than one account. Also a network can consist of computers in different cities. It calls security policies, security groups and these can only be configured to allow something. You use Access Control List ACL to deny something when setting it up. In the book there is sample policies and ACL's to make it easier to set up. You use a command line and console to set it up and you need to set it up to enable it to work.