What two features in Cisco switches help prevent Layer 2 loops? (Choose two.)

A.
Unidirectional Link Detection

B.
Hot Standby Router Protocol

C.
Virtual Router Redundancy Protocol

D.
PortFast

E.
Root guard

F.
Loop guard

Explanation:
The STP loop guard feature provides additional protection against Layer 2 forwarding loops (STP
loops). An STP loop is created when an STP blocking port in a redundant topology erroneously
transitions to the forwarding state. This usually happens because one of the ports of a physically
redundant topology (not necessarily the STP blocking port) no longer receives STP BPDUs. In its
operation, STP relies on continuous reception or transmission of BPDUs based on the port role.
The designated port transmits BPDUs, and the non-designated port receives BPDUs.