I'm teaching myself routing preparatory for the CCNA exam, and I have what should be a basic question: how do I configure PPP and/or HDLC on a router's serial subinterface?. I have some routers, but a shortage of serial cables, in a home lab. I do have some point-to-multipoint serial cables (with one serial connector on one end, a serial connector on each of the other ends), though, hence the desire to configure PPP or HDLC on serial subinterfaces.

However, on the subinterface, <encapsulation PPP> returns an error message--encapsulation is not understood. If I configure PPP on the interface, my subinterface configs are lost.

In my lab, the point-to-multipoint cables are back-to-back, and I have configured the clock rate on the DCE ends.

Any help, or pointers to docs I should be reading, would be greatly appreciated.

Eric Hines