Configure DD-WRT OpenVPN client to connect to OpenVPN server

After installing an OpenVPN server on a server, here is an explanation for newbies on how to set-up your DD-WRT (open-source router firmware) client to connect to the server. The server is configured exactly as Digital Ocean explains in their blog post.

Set up an Open-VPN server

I simply followed the tutorial on Digital Ocean: the install takes no more than 1 hour and is very straightforward. If you followed the same tuto, that means that we have the exact same type of configuration file. Otherwise, your file may differ, so you might not found this post useful to your own case.

DISCLOSURE Please note that it worked for me, but I do not gurantee anything for you: I just thought that this might help some people who run into the same questions that I did.

Client configuration file

The file generated by the bash script in the Digital Ocean tutorial looks like this

client
dev tun
proto udp
remote some.ip.address.XXX 1154
resolv-retry infinite
nobind
user nobody
group nogroup
persist-key
persist-tun
remote-cert-tls server
cipher AES-128-CBC
auth SHA256
key-direction 1
comp-lzo
verb 3

<ca>
-----BEGIN CERTIFICATE-----
XXXXXXXXXXXXXX
-----END CERTIFICATE-----
</ca>
<cert>
Certificate:
    DATA FROM CERTIFICATE...
    ...
    ...
    
-----BEGIN CERTIFICATE-----
XXXXXXX
-----END CERTIFICATE-----
</cert>
<key>
-----BEGIN PRIVATE KEY-----
XXXXXXXX
-----END PRIVATE KEY-----
</key>
<tls-auth>
#
# 2048 bit OpenVPN static key
#
-----BEGIN OpenVPN Static key V1-----
XXXXXX
-----END OpenVPN Static key V1-----
</tls-auth>

note I replaced the values of key and certificates for obvious reasons :)

Set up the DD-WRT OpenVPN client

It seems that a lot of the configuration commands (at the top of the config file) are not necessary, as DD-WRT allows you to select the correct values for each field via the GUI.

The only remaning commands I kept were

resolv-retry infinite
persist-key
persist-tun

Put these in the Additionnal Config field.

The rest of the commands must be asign to the correct fields of the GUI:

Note I had to UNCHECK the nsCertType verification checkbox, otherwise it didn’t work.

Other than that, here are the security fields to fill-up:

The others fields were left blank.

note All of those keys/certificate need to be paste with the header ---- BEGIN ... --- and the footer --- END ... --- included.

You should be all set! (at least, I am :))

Thank to egc and eibrad on the DD-WRT forum for their help