Site-to-site VPN: for what purpose do firms use it?

Anton P. | October 13, 2023

A site-to-site VPN links the networks based on remote sites into one digital ecosystem. Devices in this virtual structure can securely connect, collaborate on files, and share data.

This overview explains what a site-to-site VPN is, how it operates, and why various organizations use it.

Firms use site-to-site VPN to connect local networks of different offices into one wide area network

What is a site-to-site VPN?

One can briefly define a site-to-site VPN as combining multiple LANs to create WANs. Of course, this brief definition only makes sense after looking into what these fancy acronyms mean.

Local area network (LAN)

A local area network is any network of connected devices based in the same location. For example, a LAN can be an on-premises network of a business headquarters.

All other offices also have their local area networks. Servers and hardware devices in the building or a small building complex support each network. Being thus separated, these LANs in different geographic locations do not connect by default.

Wide area network (WAN)

A wide area network (WAN) is a network of networks spread across different geographical locations. A WAN consists of LANs via a combination of wired and wireless connections.

A site-to-site VPN is a private WAN that uses a public WAN, namely, public internet, to establish a secure connection between multiple local networks.

How does LAN traffic route to site-to-site Virtual Private Network (VPN)?

A Site-to-site VPN routes traffic between networks by establishing a private connection. Here are some of the key players involved in this process:

VPN gateway acts as the middleman between the client device and the VPN network. A server, a router, a firewall, or a similar hardware or software device can be a VPN gateway. VPN network security depends on the VPN gateway as it authenticates connections and filters traffic.
A tunneling protocol establishes a site-to-site VPN tunnel within the public internet through which data travels privately. Tunneling protocols define how data is packaged and transmitted. Site-to-site VPNs commonly use TLS protocol.
Encryption algorithms use predefined rules and unique encryption keys to encode the traffic data. Thus, even if the connection is intercepted, the hacker would only see cipher text instead of the actual message.
IP addresses that grant local access to devices from elsewhere. Firms can reuse such VPN IP addresses, for example, to allow various partner institutions to access their intranet.

Thus, when devices try to connect to remote resources on the same network, the VPN gateway routes the traffic.

The gateways create the site-to-site VPN connection but do not use it to send data the right way. They hold it to authenticate and encrypt it, thus promoting network security.

Who uses site-to-site VPN?

Organizations that spread across multiple locations need site-to-site VPNs to connect their networks. Thus, the primal users for this VPN type include:

Businesses with multiple offices in different locations. Such a business would utilize a site-to-site VPN to create a unified corporate network. Companies with a single location also utilize site-to-site VPN solutions. For example, they might need it to connect to the local networks of their client or partner companies.
Governmental institutions. They need site-to-site VPNs to effectively and privately share data between the main governmental body and its regional offices.
Science and educational institutions. University departments share information with each other and various scientific institutions, such as laboratories, using VPN connections.

Home users rarely need to conjoin private networks in different locations. Thus, site-to-site VPN is not common outside organizational settings.

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Benefits of a site-to-site Virtual Private Network (VPN)

Organizations implement site-to-site VPNs to solve a medley of problems. The main benefits of this VPN type are as follows:

Organization-wide access to the main resources. By being able to access the primary data center, teams in different locations can collaborate effectively.
Ensuring business continuity. When the physical infrastructure becomes unreachable due to emergencies, companies might still have virtual access to it. Additionally, when needed, it is easy to transfer the workload from one location to another over the WAN.
Secure communication with partner institutions. VPN data encryption allows firms to communicate confidentially with entire departments in external organizations.
Control over the network. Often, site-to-site VPNs are managed centrally. Thus, network administrators can easily control how resources are accessed and used.
Compatibility. The networks can seamlessly integrate as long as they support compatible VPN protocols. Different hardware and software tools have no problems communicating over the WAN. Additionally, organizations can easily integrate site-to-site VPN with other cyber security systems.

What other network security solutions do firms use?

Network security infrastructure continues to evolve, producing new tools and systems that organizations can use. Below are some other solutions companies use along with or instead of a site-to-site VPN.

Remote access VPN. This is another VPN type that facilitates remote work. While site-to-site VPNs connect entire networks, remote access VPNs grant access to separate employees working off-premises. Thus, companies use both VPN solutions for all-around connectivity.
Software-defined WAN (SD-WAN). Similar to software-defined perimeter (SDP), SD-WAN creates segmented areas with different access options within the WAN. While SDP, as an alternative to remote access VPN, allows employees to connect remotely, SD-WAN manages how LANs connect.
Secure Web Gateway (SWG). Like site-to-site VPNs, SWGs sit between network devices and authorize traffic. Additionally, SWGs can detect and block malicious applications.
Secure Access Service Edge (SASE). Gartner proposed SASE as a cloud-based security system that builds on the tools mentioned above. As SASE is still a relatively new idea, understanding how it should be implemented may differ. However, most agree that SASE needs to be an all-encompassing, cloud-distributed system that promotes Zero-Trust Architecture (ZTA).

Companies tend to integrate VPN technology with various network security solutions. Thus, site-to-site VPN is likely to stick around for the foreseeable future.