Site to Site VPN with PFSense and CentOS 8

On PFSense

1. Go to openvpn server creation
2. Select UDP on IPv4 only with tun
3. Use a Peer to Peer (Shared Key)
4. For the shared key automatically generate it

No other special settings required.

After you create the server, save it, and then go back in and copy the shared key.

1. Open port 1194 UDP on the firewall.

On CentOS 8

1. Make sure everything is up to date. yum update -y && reboot. The reboot is important because if your kernel might update. If this happens you need to reboot to load the new kernel.

2. Run yum install -y epel-release && yum update -y && yum install -y openvpn easy-rsa chrony && systemctl enable chronyd && chronyc makestep This is a long series of commands, but it installs openvpn and chrony. You need chrony to ensure your time is synched. WARNING: If the time is not synched between the server and your clients, the VPN will fail to connect!

3. systemctl stop firewalld - otherwise you’ll have to allow everything going to and from the networks on a case by case basis.

4. Run sysctl -w net.ipv4.ip_forward=1 && echo 1 > /proc/sys/net/ipv4/ip_forward

5. Use the following config file:

   dev ovpnc3 verb 6 dev-type tun #dev-node /dev/tun3 writepid /var/run/openvpn_client3.pid #user nobody #group nobody script-security 3 keepalive 10 60 ping-timer-rem persist-tun persist-key proto udp4 cipher AES-128-CBC auth SHA256 local lport 0 management /etc/openvpn/client3.sock unix remote 1194 udp4 ifconfig route <ROUTE FOR REMOTE NETWORK - EX 192.168.1.0> compress resolv-retry infinite secret /etc/openvpn/client/secret

In my scenario the 192.168.2.0/24 was the remote site network and 192.168.1.1 was the local network.