I tried something like this earlier this year with STP.  It got rave reviews (from my mother), so I figured I try it again.  

Below is a list of requirements for configuring a router as a call processor.  In a lab or in your head, configure the router to support the features as listed.  This isn’t a contest or anything like that.  If you get it right, a virtual thumbs up is all I can afford to give you.  There are some licensing issues for running this stuff in GNS3/dynamips, so I can’t help you out on that.  I’ll just hint that GNS3 and dynamips will bind to real networks and that copies of a compatible IP softphone are available.

Here’s an STP exercise for you.  Given the bridge priorities, MAC addresses, and interface types in the diagram, calculate the root bridge, root ports, designated ports, and blocked ports.  You can click on the image to enlarge it.  I’ll post a solution in the next few days.  As always, feel free to comment and ridicule my utter idiocy.  Be gentle, though; I don’t usually post exercises like this.

Send any configuration BPDUs questions my way.