After upgrading my OpenVPN server to CentOS 7.5 I had trouble connecting to it. Specifically, I had two different issues: ** the laptop, which is running Fedora 28, was able to connect just fine but DNS resolution was broken. ** OpenVPN for Android was also connecting just fine but reporting a weird error: OpenVPN: tun tap invalid argument (code=22). The first one was caused by me because after the CentOS upgrade procedure was completed I also run yum autoremove which deleted dnsmasq; the solution was fairly simple, reinstall and reconfigure dnsmasq. …

OpenVPN is the de facto standard VPN free open source software; it is widely used, tested, well documented and also included in the CentOS repos (EPEL). .:. Server side configuration yum install openvpn easy-rsa dnsmasq When yum is done installing the required packages, copy the sample config file. cp /usr/share/doc/openvpn-*/sample/sample-config-files/server.conf /etc/openvpn Uncomment/edit the following lines in /etc/openvpn/server.conf: port 1194 proto udp dev tun ca ca.crt cert server.crt key server.key dh dh4096. …