Not being a network expert, I spent some time configuring my network, until I found my mistake: On my HP ProCurve Switch 1810G, I thought that "Admin mode" means whether the administrative interface can be accessed from this port. Well, it means whether the port is enabled or not. Extract from the help function:
Admin Mode - Select to enable the port-control administration state. Click to enable and have the port participate in the network.(Default : Enabled )
Well, of course I didn't read the help, because I didn't doubt it's for the adminsitrative interface and suspected an error somewhere else.
Anyway, I am wondering if that is a commonly used term for enabling/disabling ports or if HP just wanted to make my life harder? I can't understand why this option isn't just called "Enable port"!?
Here's a screenshot of how it looks in the web interface (yeah, shame on me for using a web interface)