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 InterSwitch 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 protocolsCisco > Support > Configuring Spanning Tree-Protocol > How STP Works