Download the certificate chain of the certificate authorities (Telekom Root CA, DFN-PCA, Uni-CA).

Configuration file (vpn.kit.edu):

host=vpn.kit.edu
user=xxxx
password=xxxx
cafile=/path/to/chain.txt

Configuation file for Split Tunneling (vpn-split.kit.edu):

host=vpn-split.kit.edu
realm=Users-Split
user=xxxx
password=xxxx
cafile=/path/to/chain.txt

It's optional to configure the password in the configuration file.