Please remember: The RBG/ISP is not in duty for problems with the Cisco VPN client! Please contact the HRZ user support. You can also find them in the old mainbuilding S1|03 - 020. Sometimes it's also helpful to take a look FAQ (German), where you can find new tips.
To have access to the intranet and the internet, you have to authenticate yourself at first. This happens with the Cisco VPN Client. The Cisco VPN Client is a software for Windows, Linux (kernel 2.4) and MacOS. The VPN-Client-download as well as the whole site for the connection with mobile divices like smartphones is available without authentication(!). In this site can all information on installation be found.
The Cisco VPN Client produces some problems with the 2.6 Linux Kernels. Because of that there is an alternative for Linux. The project vpnc supports the main functions, but no rekeying (yet) - it might happen that one gets disconnected after one hour due to that fact. vpnc is e.g. part of Debian testing/unstable.
To connect the W-LAN there are two official SSIDs. On the one side there is “Eduroam” by the HRZ. This W-LAN works on the whole campus. To login you have to use the TUD-ID@tu-darmstadt.de with the corresponding password. You can connect to every “Eduroam” using these date - e.g. on the Campus of Goetheuniversity, other german universities, even all over Europe and in some colleges in the USA. On the other side there is the SSID TUDWeb, which is not encrypted(!). The authentication happens on a website, on which you will be redirected.
On the subject of printing via W-LAN, see also printer.