Routers allow VMs across different Networks to communicate with each other. They also play another crucial role. Routers allow VMs to communicate with entities outside the OpenStack Network such as the Internet. In Chapter 3, Exploring Other Network Types in Neutron, we introduced the concept of an external Network. External Networks, when used with a Router, allow the VM instances to access the Internet.
In order to allow VMs to access the Internet, we will need two types of Networks. A tenant Network will be used to create an instance and associate it to a Router. Next, the Router needs to be connected to an External Network that has access to the Internet. Note that an OpenStack user with the administrator's privilege can create the External Network.
This recipe assumes that the OpenStack administrator has followed the steps mentioned in the recipe titled Creating an External Networks using Horizon in Chapter 3,...