Fixing common configuration mistakes

When setting up an OpenVPN configuration, there are a few common mistakes that are easily made. These configuration mistakes can be roughly divided up into four categories:

• Certificate (PKI) errors and mismatches

• Option mismatches, such as tun versus tap, ciphers, and compression

• Insufficient privileges to run OpenVPN

• Routing mistakes

In this section, we will go through the first three of these categories. Routing mistakes will be discussed later in this chapter.

Wrong CA certificate in the client configuration

The client configuration file will almost always contain three lines like this:

ca ca.crt
cert client.crt
key client.key

These certificate and private key files were created in Chapter 3, PKIs and Certificates, and are used extensively in subsequent chapters.

The CA file, however, does not need to specify the certificate authority that was used to sign the client certificate file. It must be the public certificate of the certificate authority that was...