–IPCop. It is a free software to be installed on your existing hardware which includes packet filtering, proxy, traffic shaping, VPN and secure remote access, user authentication, name services and time server. In addition, it provides performace graphics and system monitoring to make it easy to identify any issue. It is completely free and offers community support only.
–OpenWRT. It is an access point with ethernet ports, wifi, and management software. Updating the firmware you can use it as firewall and router for small networks, as secure wireless access points, or to set up wireless hotspots. It is free os costs and no support is available.
–PfSense. This company offers a wide range of networking products, including a free community edition, hardware appliances, and cloud services. SG-2440 PfSense Security Gateway Appliance may be a good choice, since it provides secure VPN to give remote workers access to your network, policy routing, advanced routing, captive portal…
–Untangle Gateway. It manages user authentication VPN, captive portal, web filtering, anti-virus, anti-spam, intrusion prevention, ad blocker, reporting, and higher-end features such as WAN balancing and automatic failover. The basic edition is free and you can purchase different add-ons.
For more information on these systems, read the full article