Which two protocols can be automatically negotiated between switches for trunking? (Choose two.)
A.
PPP
B.
DTP
C.
ISL
D.
HDLC
E.
DLCI
F.
DOT1Q
Explanation:
Switches such as the Catalyst 3550 that are capable of either 802.1Q or ISL trunking encapsulation, the switchport trunk encapsulation [dot1q | isl | negotiate]
interface command must be used prior to the switchport mode trunk command.
https://learningnetwork.cisco.com/servlet/JiveServlet/previewBody/14792-102-1- 57313/Dynamic%20Trunking%20Protocol.PDF