A general problem you may experience is that the connection get lost after a while. I do not know exactly how long it takes, but in any case it is sufficient for work. I think it is not possible to say a concrete number of minutes because it depends whether the connection is being used. The solution is very simple: retype in the console:
./vpneui
This is a tricky problem, but is not linux specific. In some networks (I have for instance this problem in the Austrian National Library in Vienna) there is a firewall or a proxy configured in order to control/avoid connections on specific ports. The solution is here.
If you get this message
Cisco Systems VPN Client Version 4.8.00 (0490) Copyright (C) 1998-2005 Cisco Systems, Inc. All Rights Reserved. Client Type(s): Linux Running on: Linux 2.6.20-16-386 #2 Thu Jun 7 20:16:13 UTC 2007 i686 Config file directory: /etc/opt/cisco-vpnclient The application was unable to communicate with the VPN sub-system.
do not worry. I think it is only a problem with the EUI server which does not answer to our connection demand. Anyway: try again
./vpneui
and it should work...
It is possible that your VPN-Client suddenly does not work any more. If this happens, you have probably installed (without knowing it) a new version of the kernel. This happens, when you update your system (which is highly reccomendable, by the way).
Well, do not worry. Nothing is lost: you just have to follow the steps 2.1, 2.2 and 2.3 (only these steps!) from the original instructions. Here there are.
If you have installed Ubuntu 8.10 64 Bit Version you will have problems with the VPN installation. The solution is provided by Francesco Catastini (thanks!) with the following instructions.