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1. Question1 pointsWhich spanning tree standard supports only one root bridge so that traffic from all VLANs flows over the same path?CorrectIncorrect
HintMST 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.
2. Question1 pointsWhich 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.)CorrectIncorrect
HintSTP 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.
3. Question1 pointsWhich two network design features require Spanning Tree Protocol (STP) to ensure correct network operation? (Choose two.)CorrectIncorrect
HintSpanning 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.
4. Question1 pointsWhich STP priority configuration would ensure that a switch would always be the root switch?CorrectIncorrect
HintAlthough 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.
5. Question1 pointsFill in the blank. Do not use abbreviations.
- The spanning-tree (mode rapid-pvst) global configuration command is used to enable Rapid PVST+.
6. Question1 pointsWhat port type is used to interconnect switches in a switch stack?CorrectIncorrect
HintSwitches configured to operate in a switch stack are connected together through StackWise ports.
7. Question1 pointsWhat is the purpose of the Spanning Tree Protocol (STP)?CorrectIncorrect
HintThe Spanning-Tree Protocol (STP) creates one path through a switch network in order to prevent Layer 2 loops.
8. Question1 pointsWhat additional information is contained in the 12-bit extended system ID of a BPDU?CorrectIncorrect
HintThe 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.
9. Question1 pointsRefer to the exhibit. Which trunk link will not forward any traffic after the root bridge election process is complete?CorrectIncorrect
HintS4 has the lowest bridge ID, thus S4 is the root bridge. Because the path cost S1-S2-S4 is lower than the path cost S1-S3-S4, path S1-S2-S4 is the preferred path for S1 to reach S4. Thus, STP will set the S1 port Fa0/1 to a blocking state, and the trunk link Trunk2 will not forward any traffic.
10. Question1 pointsWhich 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?CorrectIncorrect
HintMST 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.
11. Question1 pointsWhich port state will switch ports immediately transition to when configured for PortFast?CorrectIncorrect
HintPortFast allows a switch port to bypass the listening and learning states and transition immediately to the forwarding state.
12. Question1 pointsRefer to the exhibit. Which switch will be elected the root bridge and which switch will place a port in blocking mode? (Choose two.)CorrectIncorrect
HintThe spanning-tree root bridge election process determines which switch becomes root bridge based first on the lowest priority number and then by lowest MAC address. Because all of the switches have the same priority value, SW3 becomes the root bridge based on lowest MAC address. To determine which ports are blocking or forwarding, first determine which ports become the root port on each switch. Then determine which port becomes the designated port for each link.
13. Question1 pointsWhat is an advantage of PVST+?CorrectIncorrect
HintPVST+ 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.
14. Question1 pointsTo 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.)CorrectIncorrect
HintThe 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.
15. Question1 pointsA 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?CorrectIncorrect
HintWhen 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.
16. Question1 pointsIf no bridge priority is configured in PVST, which criteria is considered when electing the root bridge?CorrectIncorrect
HintOnly 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.
17. Question1 pointsWhat is the outcome of a Layer 2 broadcast storm?CorrectIncorrect
HintWhen 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.
18. Question1 pointsOpen the PT Activity. Perform the tasks in the activity instructions and then answer the question. Which switch is the root bridge?CorrectIncorrect
HintClick 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.
19. Question1 pointsIn which two port states does a switch learn MAC addresses and process BPDUs in a PVST network? (Choose two.)CorrectIncorrect
HintSwitches learn MAC addresses at the learning and forwarding port states. They receive and process BPDUs at the blocking, listening, learning, and forwarding port states.
20. Question1 pointsWhich Cisco switch feature ensures that configured switch edge ports do not cause Layer 2 loops if a port is mistakenly connected to another switch?CorrectIncorrect
HintIf 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.
21. Question1 pointsWhat is a characteristic of a Layer 2 loop?CorrectIncorrect
HintA 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.
22. Question1 pointsRefer to the exhibit. What is the role of the SW3 switch?CorrectIncorrect
HintSwitch SW3 is the STP root as can be seen in the show spanning-tree command output.
23. Question1 pointsWhich three components are combined to form a bridge ID? (Choose three.)CorrectIncorrect
HintThe three components that are combined to form a bridge ID are bridge priority, extended system ID, and MAC address.
24. Question1 pointsWhich RSTP ports are connected to end devices?CorrectIncorrect
25. Question1 pointsQuestion as presented:
- Rapid PVST+
- Proprietary per VLAN implementation of IEEEE 802.1w
- Cisco implementation of IEEE 802.1D
- Fast converging enhancement of IEEE 802.1D
- IEEE standard that reduces the number of STP instances
HintMST is the Cisco implementation of MSTP (IEEE 802.1s).
26. Question1 pointsIn which two PVST+ port states are MAC addresses learned? (Choose two.)CorrectIncorrect
HintThe two PVST+ port states during which MAC addresses are learned and populate the MAC address table are the learning and the forwarding states.