apt install openvpn

openssl dhparam -out /etc/openvpn/dh2048.pem 2048

#openssl genrsa -out openvpn.key 2048
cp openvpn.key /etc/ssl/private/

#openssl req -new -x509 -days 3650 -key openvpn.key -out openvpn.crt
cp openvpn.crt /etc/ssl/certs/

#vim -c 'set ff=dos' cko-asterisk.ovpn

cp etc/openvpn/openvpn.conf /etc/openvpn/openvpn.conf

systemctl enable openvpn@openvpn
systemctl start openvpn@openvpn

# bash ../isp/scripts/createuser.bash

...
rdr proto udp from any to $ext_ip port 21956 -> 10.5.N.177 port 21956
...

[root@radio:~]# route add 172.16.3.0/24 10.5.N.177