These services offer many ways to connect, including without the service's client software; support operating systems and devices, such as routers or set-top boxes, beyond just the "big four" operating systems (Windows, Mac, Android and iOS); have hundreds, or even thousands, of servers in dozens of countries; and generally let the user sign up and pay anonymously.
An OSPF-routed network can be subdivided into areas, which are collections of contiguous networks. All areas are connected together through a common area called the backbone area. A router that connects an area to the backbone area is called an area border router (ABR). Normally, ABRs have a physical connection to the backbone area. When it is not possible or practical to have an ABR physically connected to the backbone area, administrators can use a virtual link to connect the ABR to the backbone.
In many cases, each of these offices also have LANs. But how do the LANs connect? For some very specialized solutions, companies lease private lines to connect the offices. That can be very expensive. Instead, most companies opt to geographically connect separated private LANs over the public internet. To protect their data, they set up VPNs between offices, encrypting the data as it traverses the public internet.

A remote access VPN connection over the Internet enables a remote access client to initiate a dial-up connection to a local ISP instead of connecting to a corporate or outsourced network access server (NAS). By using the established physical connection to the local ISP, the remote access client initiates a VPN connection across the Internet to the organization’s VPN server. When the VPN connection is created, the remote access client can access the resources of the private intranet. The following figure shows remote access over the Internet.

IVPN doesn’t have as many server locations as larger services like ExpressVPN do. When we initially recommended the service, IVPN was limited to 13 countries, compared with ExpressVPN’s 94. But in the months since, IVPN has doubled that to 26, including two additional locations in Asia (Tokyo and Singapore). We’ve yet to test the new servers though, and in the past, IVPN’s single location in Asia—Hong Kong—was slower than competitors.

Most VPN services allow you to connect up to five devices with a single account. Any service that offers fewer connections is outside the mainstream. Keep in mind that you'll need to connect every device in your home individually to the VPN service, so just two or three licenses won't be enough for the average nested pair. Note that many VPN services offer native apps for both Android and iOS, but that such devices count toward your total number of connections.

Every VPN will occasionally have a bad day or just a few bad hours where service is slow on a particular server or set of servers. Some VPNs have more high traffic periods or downtime than others. These are the ones to be avoided. Unfortunately, the test period for our reviews rarely lasts more than two weeks, so it’s difficult to predict what VPNs will encounter more issues in the long term at the time of writing.
Most of the popular VPNs have dedicated apps for Windows, MacOS, iOS and Android, but VPNs can also be manually configured in various ways. Most VPNs allow a number of “simultaneous connections.” What this means is that you can run VPN apps on a number of devices at the same time using the same VPN account. We now have detailed VPN setup for all major platforms, including:

Despite some of the drawbacks, ZorroVPN is a very interesting service if you are looking for advanced online anonymity. With their OpenVPN file config generator, you can create unique VPN chains with the Tor network and proxies (up to four hops). Unlike with Perfect Privacy, however, these multi-hop configurations cannot be dynamically changed within the VPN client.

To work around this problem, instead of having the client create a new default route when a connection is made, administrators can configure the client’s routing table with specific routes that direct packets to the organization’s network over the VPN connection. While connected to the intranet, the client can obtain Internet access using the default route that points to the Internet. This configuration is known as split tunneling.

While you're connected to a VPN, all your network traffic passes through this protected tunnel, and no one—not even your ISP—can see your traffic until it exits the tunnel from the VPN server and enters the public internet. If you make sure to only connect to websites secured with HTTPS, your data will continue to be encrypted even after it leaves the VPN.