One of the straightforward stories about the cloud – at least on the face of it – should have been the story about cloud networking. In order to understand how simple this story should've been, we only need to look at one number, and that number is the virtual LAN (VLAN ID) number. As you might already be aware, by using VLANs, network administrators have a chance to divide a physical network into separate logical networks. Bearing in mind that the VLAN part of the Ethernet header can have up to 12 bits, the maximum number of these logically isolated networks is 4,096. Usually, the first and last VLANs are reserved (0 and 4095), as is
So, basically, we're left with 4,093 separate logical networks in a real-life scenario, which is probably more than enough for the internal infrastructure of any given company. However, this is nowhere near enough for public cloud providers. The same problem applies to public cloud providers...