[R1]---[FRSW]---[R2] - is the topology. Everything is L2, there are no PVC's, all physical interfaces. At startup everything is running with HDLC. Enable CDP - we get CDP neighbors across the board.
Next steps - enabled FR switching on FRSW, made its interfaces FR encapsulation, switched interface type to DCE, the branch routers simply changed encapsulation to FR (so they're FR DTE's). Then manually enabled CDP on each FR interface. No CDP neighbors.
Why? CDP is a L2 technology. I show up/up for all interfaces. Thanks in advance !