preparation

*.crt Client certificate

*.key Client private key

*.takey OpenVPN TLS auth key

ca.crt CA root certificate

Server ip & port

Encryption Cipher Method, AES-256-CBC etc.

Hash Algorithm, default SHA1

ddwrt router & Linux

client
dev tun
proto udp
verb 3
syslog
remote 1.2.3.4 1194
resolv-retry infinite
nobind
user nobody
group nogroup
persist-key
persist-tun
ca ca.crt
cert client.crt
key client.key
tls-auth ta.key 1
cipher AES-256-CBC
comp-lzo
mssfix 1400

debug command

save the conf as openvpn.conf and debug using command

openvpn --config openvpn.conf

check the errors and modify conf items accordingly.

OSX

Download and install Tunnelblick conf file is the same as that of linux, then double click the conf file to load the conf file. Start openvpn in the menu bar and check logs if error occurs.