I can't setup successfully a split-VPN on Ubuntu 13.10. I followed this guide, or this or this. Adding a route manually for the VPN-secured part allows successful ping's to VPN-resources as well as standard internet domains (like google.com). ssh into a remote machine works, too. Also, syslog reports the correct nameservers. But after 1 minute or so, the VPN part stops working. ping reports unknown hosts for the private resources, ssh freezes. route still shows all correct routes, though. Looking into syslog, no error messages are available. Trying to stop/restart the VPN client does usually not help. The standard VPN setup (not trying to split the tunnel) works without problems, but does not allow any external internet addresses, of course. Any ideas?
Update: Using one of the above guides and running in a different wlan network, no problems seem to occur. So could that problem be connected to my router (a fritzbox in my case)?
Update 2: In order to check the router, I connected via a Windows machine to the VPN. The same behavour as described above can be observed -- this seems to be a problem with my router, then.