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Basically we are here telling heat to create a network for us (line 8-9) with a subnetwork connected to it (line 11-17). The subnetwork should use the address 192.168.0.0/24. Next up we create a router connected to the 'ntnu-internal' network, and attaching it to the newly created subnet. The final resource defined is a security-group allowing incoming ssh-connections from anywhere, incoming ICMP (ie: ping) from anywhere and incoming NFS-connections from any hosts at the supplied subnet.
The "get resource" functions used allows heat to reffer to resources it creates elsewhere in the template. For instance we reffer to the network "{ get_resource: network }" when creating the subnet, and that basicly means "use the ID from the network you are creating". As an alternative you could have given a network ID ther manually instead.
Actually create the resources defined in our template
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