pfSense & opnsense are opensource security appliance, the page is more focused on pfSense but the same features should be available on opnsense
The aim of this page is to provide links and information about pfSense
pfSEnse official page :https://www.pfsense.org/
opnsense official page: https://opnsense.org/
pfSense as a phyisical appliance
pfSense is openSource but some vendor are selling physical device optimised to run pfSense, physical appliances don't have the flexibility of the virtual one but they there are more efficient, they might be the right solution if your service is facing an high traffic load
here an example from the company that maintain pfsense: https://www.netgate.com/products/appliances/
pfSense as a virtual appliance
Today datacenter are often based on bare metal host running virtual machine, this setup is possible with pfSense, here an example on how to set up pfsense with vSphere: https://medium.com/@glmdev/how-to-set-up-virtualized-pfsense-on-vmware-esxi-6-x-2c2861b25931
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Multiple pfSense located in different place can setup a IPsecVPN in order to ease communication between remote servers pools
pfSense Modules
this list is not exhaustive, it shows only few modules but those are useful to setup a security layer for web servers
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