I found PFsense and OPNsense firewalls. I already have a firewall, so this post is mainly for remote I am assuming that you have the OPNsense/PFsense installed and you are able to access its webUI.
Preface [ ix ] Chapter 7, Redundancy and High Availability, discusses several ways of using pfSense to eliminate single points of failure within our network. The chapter covers gateway groups, load balancing, and Common Address Redundancy Protocol (CARP, which allows us to set up redundant firewalls).