PPPoE encapsulates PPP frames in Ethernet frames and uses common PPP features like authentication, encryption, and compression. PPPoA is used for ATM.

ATM is the Data-Link layer protocol that's typically used over the DSL layer 1 connection from the CPE and terminated at what's known as the DSLAM-an ATM switch that contains DSL interface cards, or ATU-Cs.

If you have a router in your Frame Relay network that does not support IARP, you must create Frame Relay maps on your router, which provide known DLCI-to-IP address mappings.

Clocking on a serial interface is always provided by the CSU/DSU (DCE device). However, if you do not have a CSU/DSU in your nonproduction test environment, then you need to supply clocking with the clock rate command on the serial interface of the router with the DCE cable attached.

The command debug ppp authentication will show you the authentication process that PPP uses between point-to-point connections.

If you have a serial port configured with multiple DLCIs connected to multiple remote sites, split horizon rules, stop route updates received on an interface from being sent out the same interface. By creating subinterfaces for each PVC, you can avoid the split horizon issues when using Frame Relay.

The show frame-relay ? command provides many options, but the options available in this question are lmi, pvc, and map.