B. THE CLOCK RATE COMMAND IS NEEDED ONLY WHEN A BACK-TO-BACK SERIAL...
3.
B. The clock rate command is needed only when a back-to-back serial link is created
in a lab, and this link uses a real leased line installed by a telco. Although the
bandwidth command may be recommended, it is not required to make the link work.
Because the routers are brand new, having not been configured before, the serial
interfaces still have their default encapsulation of HDLC, so the encapsulation ppp
command is required, on both routers, to make PPP operational.