Private networking is a type of network in which all the instances connected to that network are able to talk to each other and reach the rest of the Internet through a router, but the rest of the Internet cannot initialize a connection to those instances.
Private networking is ideal for running services you wish to make secure, as these services are unreachable from the Internet and thus are much harder to compromise.
Enabling private networking
Currently, the only way to enable private networking on your US-East 2 account is to contact support and request that it be enabled.
Private networking in US-East 2 is currently free of charge during its beta trial period. US-East 2 accounts also come with one floating IP address (this allows you to attach a publicly accessible IPv4 address to an instance on the private network). If additional addresses are required, they are charged at $1/month per floating IP.
Private networking is currently a beta feature, but has been well tested. One limitation currently in place is that IPv6 is not supported with private networking.
Private networking cannot be added to existing instances. This is because, much like the Key pair, the networking configuration is hard-coded into the instance during the creation process.
Once support has enabled private networking on your account, please refer to one of the following articles to setup a functional private network that instances can be attached to during the creation process.