Which protocol is used in redundant network topologies …

Which protocol is used in redundant network topologies to avoid receiving multiple copies of the same frame?

A.
802.1q

B.
Spanning Tree Protocol

C.
Cisco Discovery Protocol

D.
Routing Information Protocol

Explanation:
Spanning Tree Protocol (STP) is used to remove switching loops in redundantly configured switched environments, and to create a single active Layer 2 path
between any two network segments. This eliminates the chance of multiple copies of the same unicast frame being sent in the LAN. It also prevents broadcast
packets from creating a broadcast storm when redundant connections exist between the switches. The benefits of STP include:

Prevention of broadcast storms
Prevention of multiple frame copies
Media Access Control (MAC) address database stability
Whenever a network segment can be handled by more than one switch, STP will elect one switch to take responsibility, and the other switches will be placed into a
blocking state for the ports connected to that segment. In this way, only one switch receives and forwards data for this segment, which removes the potential for
multiple copies of the same frame being generated. For STP to provide this functionality it must be running on all of the switches. Therefore, a properly implemented
redundant topology STP is required in order to prevent multiple copies of the same unicast frame from being transmitted.
802.1q is a frame tagging method for identifying Virtual LAN (VLAN) memberships over trunk links. Frame tagging ensures identification of individual VLAN frames
over a trunk link carrying frames for multiple VLANs. This frame tagging method is a standardized protocol that was developed by The Institute of Electrical and
Electronics Engineers (IEEE). Cisco has also developed a proprietary frame tagging method known as Inter-Switch Link (ISL). 802.1q does not mitigate loops or the
reception of multiple copies of frames. The IEEE specification for STP is 802.1d.
Cisco Discovery Protocol is a Cisco proprietary protocol used to collect hardware and protocol information for directly connected Cisco devices. CDP has nothing to
do with redundant network topologies.
Routing Information Protocol (RIP) is a distance vector routing protocol. It populates routing tables dynamically about the topology changes. However, RIP does not
control the receipt of multiple copies of frames in redundant network topologies.
Objective:
LAN Switching Fundamentals
Sub-Objective:
Configure, verify, and troubleshoot STP protocols

Cisco > Support > Configuring Spanning Tree-Protocol > How STP Works