What is strongSwan?

strongSwan is an open-source IPsec-based VPN (Virtual Private Network) implementation. It runs on Linux, FreeBSD, OS X, Windows, Android, and iOS.

What is strongSwan used for?

strongSwan is a comprehensive IPsec solution that encrypts and authenticates servers and clients. strongSwan can be used to protect remote network communications, making connecting remotely the same as connecting locally.

It is open-source and acts as a keying daemon to secure connections between two hosts by utilizing the Internet Key Exchange protocols (IKEv1 and IKEv2). StrongSwan can be used to create a Virtual Private Network (VPN) in this manner. VPN connections from clients to strongSwan servers are encrypted and are a secure gateway to other servers and network resources. This enables sensitive data to be safely transferred over the Internet.

How do you use a strongSwan?

Let’s say you want to use strongSwan on Linux. strongSwan is included in most Linux distributions and is simple to install. It can be installed on hosts in your on-premises or cloud provider networks. To allow clients to send and receive traffic through strongSwan, you may need to enable IP forwarding on your interface, depending on your Linux distribution.

Installing and configuring strongswan requires setting up your configuration and files and restarting the service. Depending on where and how you’ll be using strongswan, you should follow a step-by-step guide for your system.

What is the history behind this protocol?

strongSwan emerged in 2005 as a branch of the now-defunct FreeS/WAN open-source project.

Since then, a new IKE daemon has been created from the ground up in a modern object-oriented coding approach, and the current code base no longer shares code with its ancestor. That daemon’s modular design enables customization via an expanding number of plugins.

Initially, only IKEv2 was supported by the new daemon, while IKEv1 was handled by an expanded version of FreeS/WAN’s Pluto daemon. However, because other vendors’ adoption of IKEv2 took longer than expected, support for IKEv1 was added to the new daemon with strongSwan 5.0 in 2012, which eliminated Pluto and many other legacy components.

What ports does strongSwan use?

The standard connection implementation is limited to listening on two predefined ports. strongSwan has compile-time options and two settings to choose these ports; however, most clients will utilize the default ports 500/4500. To use ephemeral source ports on a client, set these parameters to 0, and the plugin will identify them when it is initialized.

As a client, strongSwan can connect to any remote port. There is also an experimental connection implementation called socket-dynamic, which may deliver IKE messages from particular source ports and require packets to be sent to the remote NAT-T port.

Wrapping up

strongSwan can be utilized to safeguard remote network communications, enabling connecting remotely identical to connecting locally. It might seem tricky to grasp how strongSwan works; however, there are resources on installing it on the official website if you want powerful encryption for your IP traffic. 

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