CCNA 3 Chapter 3: STP (v5.0.3 + v6.0) Exam Answers – 100% Result

Q1. Which spanning tree standard supports only one root bridge so that traffic from all VLANs flows over the same path?

• 802.1D
• PVST+
• Rapid
• PVST
• MST

Explanation:  MST is the Cisco implementation of MSTP, an IEEE standard protocol that provides up to 16 instances of RSTP. PVST+ provides a separate 802.1D spanning-tree instance for each VLAN that is configured in the network. 802.1D is the original STP standard defined by the IEEE and allows for only one root bridge for all VLANs. 802.1w, or RSTP, provides faster convergence but still uses only one STP instance for all VLANs.

Discussion

Q2. Which two types of spanning tree protocols can cause suboptimal traffic flows because they assume only one spanning-tree instance for the entire bridged network? (Choose two.)

• STP
• MSTP
• RSTP
• PVST+
• Rapid PVST+

Explanation:  STP and RSTP assume only one IEEE 802.1D spanning-tree instance for the entire bridged network irrespective of the number of VLANs, This can result in suboptimal traffic flow issues. PVST+ provides a separate spanning-tree instance for each VLAN configured. Rapid PVST+ provides a separate instance of 802.1w per VLAN, and MSTP maps multiple VLANs that have the same traffic flow requirements into the same spanning-tree instance but allows for more than one instance for dissimilar traffic flows.

Discussion

Q3. In which two PVST+ port states are MAC addresses learned? (Choose two.)

• listeningblocking
• forwarding
• learning
• disabled

Explanation:  The two PVST+ port states during which MAC addresses are learned and populate the MAC address table are the learning and the forwarding states.

Discussion

Q4. Which two network design features require Spanning Tree Protocol (STP) to ensure correct network operation? (Choose two.)

• redundant links between Layer 2 switches
• link-state dynamic routing that provides redundant routes
• implementing VLANs to contain broadcasts
• static default routes
• removing single points of failure with multiple Layer 2 switches

Explanation:  Spanning Tree Protocol (STP) is required to ensure correct network operation when designing a network with multiple interconnected Layer 2 switches or using redundant links to eliminate single points of failure between Layer 2 switches. Routing is a Layer 3 function and does not relate to STP. VLANs do reduce the number of broadcast domains but relate to Layer 3 subnets, not STP.

Discussion

Q5. Which STP priority configuration would ensure that a switch would always be the root switch?

• spanning-tree vlan 10 root primary
• spanning-tree vlan 10 priority 0
• spanning-tree vlan 10 priority 4096
• spanning-tree vlan 10 priority 61440

Explanation:  Although the spanning-tree vlan 10 root primary command will ensure a switch will have a bridge priority value lower than other bridges introduced to the network, the spanning-tree vlan 10 priority 0 command ensures the bridge priority takes precedence over all other priorities.

Discussion

Q6. Fill in the blank. Do not use abbreviations.

The spanning-tree mode rapid-pvst global configuration command is used to enable Rapid PVST+.

Explanation:  No answer description available for this question

Discussion

Q7. What port type is used to interconnect switches in a switch stack?

• designated
• StackWise
• root
• edge

Explanation:  Switches configured to operate in a switch stack are connected together through StackWise ports.

Discussion

Q8. What is the purpose of the Spanning Tree Protocol (STP)?

• prevents Layer 2 loops
• prevents routing loops on a router
• creates smaller broadcast domains
• allows Cisco devices to exchange routing table updates
• creates smaller collision domains

Explanation:  The Spanning-Tree Protocol (STP) creates one path through a switch network in order to prevent Layer 2 loops.

Discussion

Q9. What additional information is contained in the 12-bit extended system ID of a BPDU?

• MAC address
• port ID
• VLAN ID
• IP address

Explanation:  The BPDU has three fields; the bridge priority, the extended system ID, and the MAC address. The extended system ID contains 12 bits that identify the VLAN ID.

Discussion

Q10. Question

Explanation:  No answer description available for this question

Discussion

Q11. Which protocol provides up to 16 instances of RSTP, combines many VLANs with the same physical and logical topology into a common RSTP instance, and provides support for PortFast, BPDU guard, BPDU filter, root guard, and loop guard?

• STP
• PVST+
• MST
• Rapid PVST+

Explanation:  MST is the Cisco implementation of MSTP, an IEEE standard protocol that provides up to 16 instances of RSTP and combines many VLANs with the same physical and logical topology into a common RSTP instance. Each instance supports PortFast, BPDU guard, BPDU filter, root guard, and loop guard. STP and RSTP assume only one spanning-tree instance for the entire bridged network, regardless of the number of VLANs. PVST+ provides a separate 802.1D spanning-tree instance for each VLAN that is configured in the network.

Discussion

Q12. Which port state will switch ports immediately transition to when configured for PortFast?

• learning
• forwarding
• blocking
• listening

Explanation:  PortFast allows a switch port to bypass the listening and learning states and transition immediately to the forwarding state.

Discussion

Q13. Question

Explanation:  No answer description available for this question

Discussion

Q14. What is an advantage of PVST+?

• PVST+ optimizes performance on the network through autoselection of the root bridge.
• PVST+ reduces bandwidth consumption compared to traditional implementations of STP that use CST.
• PVST+ requires fewer CPU cycles for all the switches in the network.
• PVST+ optimizes performance on the network through load sharing.

Explanation:  PVST+ results in optimum load balancing. However, this is accomplished by manually configuring switches to be elected as root bridges for different VLANs on the network. The root bridges are not automatically selected. Furthermore, having spanning-tree instances for each VLAN actually consumes more bandwidth and it increases the CPU cycles for all the switches in the network.

Discussion

Q15. To obtain an overview of the spanning tree status of a switched network, a network engineer issues the show spanning-tree command on a switch. Which two items of information will this command display? (Choose two.)

• The role of the ports in all VLANs.
• The root bridge BID.
• The number of broadcasts received on each root port.
• The IP address of the management VLAN interface.
• The status of native VLAN ports.

Explanation:  The show spanning-tree command will display the status of STP for all VLANs that are defined on a switch and other information including the root bridge BID. It does not show the number of broadcast packets received on the ports. The IP address of the management VLAN interface is not related to STP and is displayed by the show running-configuration command.

Discussion

Q16. A network administrator is preparing the implementation of Rapid PVST+ on a production network. How are the Rapid PVST+ link types determined on the switch interfaces?

• Link types can only be determined if PortFast has been configured.
• Link types are determined automatically.
• Link types must be configured with specific port configuration commands.
• Link types can only be configured on access ports configured with a single VLAN.

Explanation:  When Rapid PVST+ is being implemented, link types are automatically determined but can be specified manually. Link types can be either point-to-point, shared, or edge.

Discussion

Q17. If no bridge priority is configured in PVST, which criteria is considered when electing the root bridge?

• highest MAC address
• lowest MAC address
• lowest IP address
• highest IP address

Explanation:  Only one switch can be the root bridge for a VLAN. The root bridge is the switch with the lowest BID. The BID is determined by priority and the MAC address. If no priority is configured then all switches use the default priority and the election of the root bridge will be based on the lowest MAC address.

Discussion

Q18. What is the outcome of a Layer 2 broadcast storm?

• ARP broadcast requests are returned to the transmitting host.
• CSMA/CD will cause each host to continue transmitting frames.
• New traffic is discarded by the switch because it is unable to be processed.
• Routers will take over the forwarding of frames as switches become congested.

Explanation:  When the network is saturated with broadcast traffic that is looping between switches, new traffic is discarded by each switch because it is unable to be processed.

Discussion

Q19. Open the PT Activity. Perform the tasks in the activity instructions and then answer the question. Which switch is the root bridge?

• Switch_4
• Switch_1
• Switch_3
• Switch_2

Explanation:  Click on each PC.
Use the Terminal application.
Issue the command show spanning-tree.
The switch that is the root bridge will be stated in the root bridge MAC address field.

Discussion

Q20. In which two port states does a switch learn MAC addresses and process BPDUs in a PVST network? (Choose two.)

• disabledblocking
• listening
• forwarding
• learning

Explanation:  Switches learn MAC addresses at the learning and forwarding port states. They receive and process BPDUs at the blocking, listening, learning, and forwarding port states.

Discussion

Q21. Which Cisco switch feature ensures that configured switch edge ports do not cause Layer 2 loops if a port is mistakenly connected to another switch?

• PortFast
• extended system ID
• BPDU guard
• PVST+

Explanation:  If switch access ports are configured as edge ports using PortFast, BPDUs should never be received on those ports. Cisco switches support a feature called BPDU guard. When it is enabled, BPDU guard will put an edge port in an error-disabled state if a BPDU is received by the port. This will prevent a Layer 2 loop occurring. PVST+ is an implementation of the Spanning Tree Protocol. The extended system ID is a mechanism of including VLAN ID information in the bridge ID (BID) for each VLAN.

Discussion

Q22. What is a characteristic of a Layer 2 loop?

• Broadcast frames are forwarded back to the sending switch.
• The Time-to-Live attribute of a frame is set to infinity.
• Routers continually forward packets to other routers.
• A switch is continually forwarding the same unicast frame.

Explanation:  A Layer 2 loop occurs when broadcast frames are forwarded back to the sending switch via a backup link. Layer 2 frames do not have a Time-to-Live (TTL) attribute. Routers forward packets at Layer 3 (the network layer) not Layer 2.

Discussion

Q23. Question

Explanation:  No answer description available for this question

Discussion

Q24. Which three components are combined to form a bridge ID?

• MAC address
• extended system ID
• IP address
• cost
• bridge priority
• port ID

Explanation:  The three components that are combined to form a bridge ID are bridge priority, extended system ID, and MAC address.

Discussion

Q25. Which RSTP ports are connected to end devices?

• edge ports
• designated port
• strunk ports
• root ports

Explanation:  No answer description available for this question

Discussion

Q26. Question

Explanation:  No answer description available for this question

Discussion

Q27. Question

Explanation:  No answer description available for this question

Discussion

Q28. What is the most cost-effective method of solving interface congestion that is caused by a high level of traffic between two switches?

• increase uplink speed
• add more VLANs to reduce broadcast domains
• aggregate ports by using EtherChannel
• insert a router between the switches

Explanation:  No answer description available for this question

Discussion

Q29. Which two load balancing methods can be implemented with EtherChannel technology? (Choose two.)

• destination MAC to destination IP
• destination IP to destination MAC
• source MAC to destination MAC
• source IP to destination IP
• destination MAC to source MAC
• destination IP to source IP

Explanation:  Source MAC to destination MAC load balancing and source IP to destination IP load balancing are two implementation methods used in EtherChannel technology.

Discussion

Q30. Which statement describes an EtherChannel implementation?

• EtherChannel operates only at Layer 2.
• PAgP cannot be used in conjunction with EtherChannel.
• A trunked port can be part of an EtherChannel bundle.
• EtherChannel can support up to a maximum of ten separate links.

Explanation:  No answer description available for this question

Discussion

Q31. What is an advantage of using LACP?

• increases redundancy to Layer 3 devices
• decreases the chance of a spanning-tree loop
• allows automatic formation of EtherChannel links
• provides a simulated environment for testing link aggregation
• decreases the amount of configuration that is needed on a switch for EtherChannel

Explanation:  No answer description available for this question

Discussion

Q32. Which statement is true regarding the use of PAgP to create EtherChannels?

• It requires full duplex.
• It is Cisco proprietary.
• It requires more physical links than LACP does.
• It increases the number of ports that are participating in spanning tree.
• It mandates that an even number of ports (2, 4, 6, etc.) be used for aggregation.

Explanation:  No answer description available for this question

Discussion

Q33. Which two protocols are link aggregation protocols? (Choose two.)

• 802.3ad
• PAgP
• STP
• EtherChannel
• RSTP

Explanation:  The two protocols that can be used to form an EtherChannel are PAgP (Cisco proprietary) and LACP, also know as IEEE 802.3ad. STP (Spanning Tree Protocol) or RSTP (Rapid Spanning Tree Protocol) is used to avoid loops in a Layer 2 network. EtherChannel is the term that describes the bundling of two or more links that are treated as a single link for spanning tree and configuration.

Discussion

Q34. Which PAgP mode combination will establish an EtherChannel?

• switch 1 set to on; switch 2 set to desirable.
• switch 1 set to desirable; switch 2 set to desirable.
• switch 1 set to auto; switch 2 set to auto.
• switch 1 set to auto; switch 2 set to on.

Explanation:  No answer description available for this question

Discussion

Q35. Question

Explanation:  No answer description available for this question

Discussion

Q36. When a range of ports is being configured for EtherChannel, which mode will configure LACP so that it initiates the EtherChannel negotiation?

• active
• auto
• desirable
• passive

Explanation:  The command channel-group mode active enables LACP unconditionally, and the command channel-group mode passive enables LACP only if the port receives an LACP packet from another device. The command channel-group mode desirable enables PAgP unconditionally, and the command channel-group mode auto enables PAgP only if the port receives a PAgP packet from another device.

Discussion

Q37. When a range of ports is being configured for EtherChannel by the use of PAgP, which mode will form the bundled channel only if the port receives PAgP packets from another device?

• active
• auto
• desirable
• passive

Explanation:  The command channel-group mode active enables LACP unconditionally, and the command channel-group mode passive enables LACP only if the port receives an LACP packet from another device. The command channel-group mode desirable enables PAgP unconditionally, and the command channel-group mode auto enables PAgP only if the port receives a PAgP packet from another device.

Discussion

Q38. As the network administrator you have been asked to implement EtherChannel on the corporate network. What does this configuration consist of?

• providing redundant links that dynamically block or forward traffic
• grouping multiple physical ports to increase bandwidth between two switches
• grouping two devices to share a virtual IP address
• providing redundant devices to allow traffic to flow in the event of device failure

Explanation:  No answer description available for this question

Discussion

Q39. Question

Explanation:  No answer description available for this question

Discussion

Q40. Which command will initiate EtherChannel interface configuration mode?

• channel-group group-identifier
• interface port-channel interface-identifier
• interface interface-identifier
• interface range interface-identifier

Explanation:  No answer description available for this question

Discussion

Q41. What is a best practice to use before beginning an EtherChannel implementation?

• Assign affected interfaces to VLAN 1.
• Assign affected interfaces to the management VLAN.
• Shut down each of the affected interfaces.
• Enable each of the affected interfaces.
• Assign affected interfaces to an unused VLAN.

Explanation:  No answer description available for this question

Discussion

Q42. Which three options must match in order to establish an EtherChannel between two directly connected switches? (Choose three.)

• port numbers that are used for the EtherChannel
• VLAN memberships of the interfaces that are used for EtherChannel
• domain names on the switches
• speed of the interfaces that are used for EtherChannel
• duplex settings of the interfaces that are used for EtherChannel
• port security settings on the interfaces that used for EtherChannel

Explanation:  No answer description available for this question

Discussion

Q43. An EtherChannel link using LACP was formed between two switches, S1 and S2. While verifying the configuration, which mode combination could be utilized on both switches?

• S1-on and S2-passive
• S1-passive and S2-passive
• S1-on and S2-active
• S1-passive and S2-active

Explanation:  No answer description available for this question

Discussion

Q44. Question

Explanation:  No answer description available for this question

Discussion

Q45. The trunk link between two 2960 switches has reached its capacity. How can this be addressed in the most economical way?

• Increase the speed of the ports.
• Decrease the size of the inter-switch collision domain by configuring additional VLANs.
• Combine physical ports into a high-speed logical link by configuring EtherChannel.
• Create additional broadcast domains by inserting a router between the switches.

Explanation:  No answer description available for this question

Discussion

Q46. Which statement describes a characteristic of EtherChannel?

• It can combine up to a maximum of 4 physical links.
• It can bundle mixed types of 100 Mb/s and 1Gb/s Ethernet links.
• It consists of multiple parallel links between a switch and a router.
• It is made by combining multiple physical links that are seen as one link between two switches.

Explanation:  No answer description available for this question

Discussion

Q47. What are two advantages of using LACP? (Choose two.)

• increases redundancy to Layer 3 devices
• eliminates the need for the spanning-tree protocol
• allows automatic formation of EtherChannel links
• provides a simulated environment for testing link aggregation
• decreases the amount of configuration that is needed on a switch for EtherChannel
• allows use of multivendor devices

Explanation:  No answer description available for this question

Discussion

Q48. Which three settings must match in order for switch ports to form an EtherChannel? (Choose three.)

• The switch port numbers that will be combined to form the EtherChannel must match.
• Non-trunk ports must belong to the same VLAN.
• The SNMP community strings must be configured the same.
• The interfaces must be configured to the same speed.
• The duplex settings of the switch ports on both sides of the physical link must match.
• Port security settings on the connected physical interfaces must be configured to the same violation mode.

Explanation:  Speed and duplex settings must match for all interfaces in an EtherChannel. All interfaces in the EtherChannel must be in the same VLAN if the ports are not configured as trunks. Any ports may be used to establish an EtherChannel. SNMP community strings and port security settings are not relevant to EtherChannel.

Discussion

Q49. A network administrator is configuring an EtherChannel link between switches SW1 and SW2 by using the command SW1(config-if-range)# channel-group 1 mode passive. Which command must be used on SW2 to enable this EtherChannel?

• SW2(config-if-range)# channel-group 1 mode auto
• SW2(config-if-range)# channel-group 1 mode active
• SW2(config-if-range)# channel-group 1 mode passive
• SW2(config-if-range)# channel-group 1 mode desirable

Explanation:  No answer description available for this question

Discussion

Q50. Question

Explanation:  No answer description available for this question

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Q51. Question

Explanation:  No answer description available for this question

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Q52. Question

Explanation:  No answer description available for this question

Discussion

Q53. Question

Explanation:  No answer description available for this question

Discussion