So another problem for Paul is he wants these VMS VM one and VM two to be in the same subnet.
But Peter, the network guy won't allow that.
He wants to implement a rooted infrastructure, so to contain broadcasts and for better network design.
Peter, the network engineer, wants the VMs to be in separate VLANs and tells Paul that a VLAN cannot
span across the data center.
So VM one and VM two need to be in separate subnets.
Now, this is a problem for Paul.
He wants to have VMs on multiple hypervisors in the same subnet, so he wants a VM running on ESXi server
on the left as well as iSCSI server on the right as well as on say a KVM server or other ESXi servers.
All those virtual machines need to be in the same subnet.
So he wants to span subnets across the data center.
Peter, however, says that's not possible.
Another advantage for the overlay setup is the virtual machines can be in the same subnet.
So VM one and VM two can be in the same subnet, even though they span across a routed infrastructure.
So there's nothing stopping virtual machine one, virtual machine two, virtual machine three and virtual
machine four all being in the same subnet.
Even though they span different parts of the data center, the tunnels between the hypervisors can be
dynamically set up and torn down depending on where the VMs are.
So if a virtual machine is moved via the motion to a different ESXi server, the VXLAN tunnel can automatically
be torn down and re-established to the new hypervisor.
Basically, with a virtual network or an overlay network, the server administrator can create and tear
down virtual networks without involving the network administrator.
The physical infrastructure simply needs to move traffic from one part of the network to another part
of the network.
Now, obviously, you need to think about quality of service and other factors, but the moral of the
story is the network administrator's role and responsibilities has been reduced dramatically.
By using an orchestration tool, the server administrator can dynamically, efficiently and very quickly
at scale deploy virtual networks.
And I'm going to show you an example of that in a moment.