A network administrator is having difficulty in establishing a serial link between a Cisco router and
a router from another vendor. Both routers are configured for HDLC encapsulation. Which
statements are true regarding this configuration? (Choose two.)

A.
The Cisco HDLC frame uses a proprietary “Type” field that may not be compatible with
equipment of other vendors.

B.
HDLC requires a clock rate to be configured on the routers at both ends of the serial link.

C.
PPP encapsulation is recommended for serial links between equipment from multiple vendors.

D.
Usernames must be configured at both ends of the HDLC serial link

E.
The HDLC vendor type must be enabled on the Cisco router.

F.
There is a mismatch in the HDLC authentication password configurations.

Explanation: