LAN Switching And Wireless - Chapter 5 Exam
CCNA Exploration v4 - Networking 207 (LAN Switching and Wireless) - Chapter 5 Exam
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See File "Net207 Chapter 5 Exam Modules" on flash drive for Figures and examples
- 1.
Which two criteria does a switch use to select the root bridge? (Choose two.)
- A.
Bridge priority
- B.
Switching speed
- C.
Number of ports
- D.
Base MAC address
- E.
Switch location
- F.
Memory size
Correct Answer(s)
A. Bridge priority
D. Base MAC addressExplanation
A switch uses bridge priority and base MAC address to select the root bridge. Bridge priority is a value assigned to each switch, and the switch with the lowest bridge priority becomes the root bridge. The base MAC address is also used in the selection process, with the switch having the lowest base MAC address being chosen as the root bridge. These two criteria help determine the hierarchy and path selection in a spanning tree network.Rate this question:
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- 2.
Which two statements are true about the default operation of STP in a Layer 2 switched environment that has redundant connections between switches? (Choose two.)
- A.
The root switch is the switch with the highest speed ports.
- B.
Decisions on which port to block when two ports have equal cost depend on the port priority and identity.
- C.
All trunking ports are designated and not blocked.
- D.
Root switches have all ports set as root ports.
- E.
Non-root switches each have only one root port.
Correct Answer(s)
B. Decisions on which port to block when two ports have equal cost depend on the port priority and identity.
E. Non-root switches each have only one root port.Explanation
In a Layer 2 switched environment with redundant connections between switches, two statements are true about the default operation of STP. Firstly, decisions on which port to block when two ports have equal cost depend on the port priority and identity. This means that the switch will choose which port to block based on the priority assigned to each port. Secondly, non-root switches each have only one root port. This means that non-root switches will have one designated port that is connected to the root switch.Rate this question:
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- 3.
Refer to the exhibit CH5-1 (on flash drive). All switches in the network have empty MAC tables. STP has been disabled on the switches in the network. How will a broadcast frame that is sent by host PC1 be handled on the network?
- A.
Switch SW1 will block the broadcast and drop the frame.
- B.
Switch SW1 will forward the broadcast out all switch ports, except the originating port. This will generate an endless loop in the network.
- C.
Switch SW1 will forward the broadcast out all switch ports, except the originating port. All hosts in the network will reply with a unicast frame sent to host PC1.
- D.
Switch SW1 will forward the traffic out all switch ports except the originating port as a unicast frame. All hosts in the network will reply with a unicast frame sent to switch SW1.
Correct Answer
B. Switch SW1 will forward the broadcast out all switch ports, except the originating port. This will generate an endless loop in the network. -
- 4.
Which two statements describe the BIDs used in a spanning tree topology? (Choose two.)
- A.
They are sent out by the root bridge only after the inferior BPDUs are sent.
- B.
They consist of a bridge priority and MAC address.
- C.
Only the root bridge will send out a BID.
- D.
They are used by the switches in a spanning tree topology to elect the root bridge.
- E.
The switch with the fastest processor will have the lowest BID.
Correct Answer(s)
B. They consist of a bridge priority and MAC address.
D. They are used by the switches in a spanning tree topology to elect the root bridge.Explanation
BIDs (Bridge IDs) in a spanning tree topology consist of a bridge priority and MAC address. They are used by the switches in the topology to elect the root bridge. The bridge with the lowest BID becomes the root bridge. The BIDs are not sent out by the root bridge only after the inferior BPDUs (Bridge Protocol Data Units) are sent, and it is not true that only the root bridge sends out a BID. The BID is not determined by the processor speed of the switch.Rate this question:
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- 5.
Which statement or set of paired statements correctly compares STP with RSTP?
- A.
STP and RSTP have the same BPDU format and flag field information.
- B.
STP specifies backup ports. RSTP has only root ports, alternate ports, and designated ports.
- C.
STP port states are independent of port roles. RSTP ties together the port state and port role.
- D.
STP waits for the network to converge before placing ports into forwarding state. RSTP places designated ports into forwarding state immediately.
Correct Answer
D. STP waits for the network to converge before placing ports into forwarding state. RSTP places designated ports into forwarding state immediately.Explanation
STP and RSTP differ in their behavior regarding the convergence of the network and the forwarding of designated ports. STP waits for the network to converge, ensuring that all bridges in the network have exchanged BPDU messages and determined the root bridge, before it places ports into the forwarding state. On the other hand, RSTP places designated ports into the forwarding state immediately, without waiting for the network to converge. This allows RSTP to provide faster convergence and reduce the time it takes for a port to become operational.Rate this question:
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- 6.
How can a network administrator influence which STP switch becomes the root bridge?
- A.
Configure all the interfaces on the switch as the static root ports.
- B.
Change the BPDU to a lower value than that of the other switches in the network.
- C.
Assign a lower IP address to the switch than that of the other switches in the network.
- D.
Set the switch priority to a smaller value than that of the other switches in the network.
Correct Answer
D. Set the switch priority to a smaller value than that of the other switches in the network.Explanation
By setting the switch priority to a smaller value than that of the other switches in the network, the network administrator can influence which STP switch becomes the root bridge. The switch with the lowest priority value will become the root bridge.Rate this question:
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- 7.
In which STP state does a port record MAC addresses but not forward user data?
- A.
Blocking
- B.
Learning
- C.
Disabling
- D.
Listening
- E.
Forwarding
Correct Answer
B. LearningExplanation
In the learning state of STP (Spanning Tree Protocol), a port records MAC addresses but does not forward user data. This is because in the learning state, the port is still in the process of learning the network topology and building its MAC address table. Once the learning process is complete, the port transitions to the forwarding state, where it starts forwarding user data.Rate this question:
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- 8.
When PVST+ was developed, the Bridge ID was modified to include which information?
- A.
Bridge priority
- B.
MAC address
- C.
Protocol
- D.
VLAN ID
Correct Answer
D. VLAN IDExplanation
When PVST+ was developed, the Bridge ID was modified to include the VLAN ID information. The Bridge ID is a unique identifier for each bridge in a spanning tree network. By including the VLAN ID in the Bridge ID, PVST+ allows for the creation of separate spanning tree instances for each VLAN. This ensures that each VLAN has its own independent spanning tree, improving network efficiency and reducing the risk of broadcast storms.Rate this question:
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- 9.
What is the first step in the process of convergence in a spanning tree topology?
- A.
Election of the root bridge
- B.
Blocking of the non-designated ports
- C.
Selection of the designated trunk port
- D.
Determination of the designated port for each segment
Correct Answer
A. Election of the root bridgeExplanation
In a spanning tree topology, the first step in the process of convergence is the election of the root bridge. The root bridge is the central point of the spanning tree and is responsible for making decisions about the forwarding path of data. By electing a root bridge, the network can establish a hierarchical structure and determine the designated ports for each segment, which helps in preventing loops and ensuring efficient data transmission.Rate this question:
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- 10.
What two elements will exist in a converged network with one spanning tree? (Choose two.)
- A.
One root bridge per network
- B.
All non-designated ports forwarding
- C.
One root port per non-root bridge
- D.
Multiple designated ports per segment
- E.
One designated port per network
Correct Answer(s)
A. One root bridge per network
C. One root port per non-root bridgeExplanation
In a converged network with one spanning tree, there will be one root bridge per network. The root bridge is the central point of the network and all other bridges or switches in the network will have a designated role in relation to the root bridge. Additionally, there will be one root port per non-root bridge. The root port is the port on a non-root bridge that provides the shortest path to the root bridge. These two elements are essential in ensuring a stable and efficient network topology.Rate this question:
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- 11.
Refer to the exhibit CH5-2. What can be determined from the output shown?
- A.
Two hosts communicating between ports Fa0/2 and Fa0/4 have a cost of 38.
- B.
The priority was statically configured to identify the root.
- C.
STP is disabled on this switch.
- D.
The timers have been altered to reduce convergence time.
Correct Answer
B. The priority was statically configured to identify the root.Explanation
The given output suggests that the priority was statically configured to identify the root. This means that a specific switch has been designated as the root bridge in the spanning tree protocol (STP) network. By configuring the priority, the network administrator ensures that this switch will always be elected as the root bridge, which helps in determining the best path for forwarding traffic in the network.Rate this question:
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- 12.
What two features of the Spanning-Tree Protocol contribute to the time it takes for a switched network to converge after a topology change occurs? (Choose two.)
- A.
The max-age timer
- B.
The spanning-tree hold down timer
- C.
The forward delay
- D.
The spanning-tree path cost
- E.
The blocking delay
Correct Answer(s)
A. The max-age timer
C. The forward delayExplanation
The max-age timer is a feature of the Spanning-Tree Protocol that contributes to the time it takes for a switched network to converge after a topology change. This timer determines the maximum age of a BPDU (Bridge Protocol Data Unit) before it is considered invalid. When a topology change occurs, the max-age timer ensures that the network waits for the specified time before considering the old BPDU information as invalid and initiating the convergence process.
The forward delay is another feature that contributes to the convergence time. This delay is the amount of time a switch waits before transitioning a port from blocking to forwarding state. During this delay, the switch listens for BPDUs to ensure that no loops are present in the network. The forward delay allows the network to stabilize and ensure that all switches have updated information before allowing traffic to flow through the newly enabled port.
Both the max-age timer and the forward delay help in preventing loops and ensuring a stable network topology, which ultimately contribute to the time it takes for a switched network to converge after a topology change.Rate this question:
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- 13.
What three link types have been defined for Rapid Spanning-Tree Protocol? (Choose three.)
- A.
Shared
- B.
End-to-end
- C.
Edge-type
- D.
Boundary-type
- E.
Point-to-many
- F.
Point-to-point
Correct Answer(s)
A. Shared
C. Edge-type
F. Point-to-pointExplanation
The three link types defined for Rapid Spanning-Tree Protocol are shared, edge-type, and point-to-point. The shared link type refers to a link that is shared by multiple VLANs. The edge-type link is a link that connects directly to an end device, such as a host or a server. The point-to-point link is a link that connects two switches directly without any other devices in between.Rate this question:
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- 14.
Refer to the exhibit CH5-3 (on flash drive). The spanning-tree port priority of each interface is at the default setting. The network administrator enters the spanning-tree vlan 1 root primary command on S4. What is the effect of the command?
- A.
Spanning tree blocks Gi0/1 on S3.
- B.
Gi0/2 on S3 transitions to a root port.
- C.
Port priority makes Gi0/2 on S1 a root port.
- D.
S4 is already the root bridge, so there are no port changes.
Correct Answer
B. Gi0/2 on S3 transitions to a root port.Explanation
The command "spanning-tree vlan 1 root primary" on S4 will cause Gi0/2 on S3 to transition to a root port. This command sets the priority of the root bridge for VLAN 1 to the lowest value, making S4 the root bridge. As a result, S3 will compare the priorities of its own interfaces, and since Gi0/2 has the lowest priority, it will become the root port.Rate this question:
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- 15.
In which two ways is the information that is contained in BPDUs used by switches? (Choose two.)
- A.
To negotiate a trunk between switches
- B.
To set the duplex mode of a redundant link
- C.
To identify the shortest path to the root bridge
- D.
To prevent loops by sharing bridging tables between connected switches
- E.
To determine which ports will forward frames as part of the spanning tree
Correct Answer(s)
C. To identify the shortest path to the root bridge
E. To determine which ports will forward frames as part of the spanning treeExplanation
BPDUs (Bridge Protocol Data Units) are used by switches in two ways. Firstly, they are used to identify the shortest path to the root bridge. BPDUs contain information about the bridge ID, path cost, and port ID, which allows switches to determine the most efficient path to the root bridge. Secondly, BPDUs are used to determine which ports will forward frames as part of the spanning tree. By exchanging BPDUs, switches can establish which ports should be in forwarding mode and which should be in blocking mode, preventing loops in the network.Rate this question:
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- 16.
What Rapid Spanning Tree Protocol (RSTP) role is assigned to the forwarding port elected for every Ethernet LAN segment that links two switches?
- A.
Alternate
- B.
Backup
- C.
Designated
- D.
Edge
Correct Answer
C. DesignatedExplanation
In the Rapid Spanning Tree Protocol (RSTP), the role assigned to the forwarding port elected for every Ethernet LAN segment that links two switches is "designated". This means that the port has been selected as the primary port for forwarding data packets on that particular segment. It is responsible for transmitting and receiving network traffic efficiently, ensuring a stable and reliable network connection between the switches.Rate this question:
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- 17.
Which two items are true regarding the spanning-tree portfast command? (Choose two.)
- A.
PortFast is Cisco proprietary.
- B.
PortFast can negatively effect DHCP services.
- C.
PortFast is used to more quickly prevent and eliminate bridging loops.
- D.
Enabling PortFast on trunks that connect to other switches improves convergence.
- E.
If an access port is configured with PortFast, it immediately transitions from a blocking to a forwarding state.
Correct Answer(s)
A. PortFast is Cisco proprietary.
E. If an access port is configured with PortFast, it immediately transitions from a blocking to a forwarding state.Explanation
PortFast is a Cisco proprietary feature that allows an access port to immediately transition from a blocking state to a forwarding state, bypassing the usual listening and learning states. This helps to prevent and eliminate bridging loops more quickly, improving network convergence. However, enabling PortFast on trunks that connect to other switches can cause issues as it can lead to loops and negatively affect DHCP services.Rate this question:
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- 18.
Which two actions does an RSTP edge port take if it receives a BPDU? (Choose two.)
- A.
Immediately loses its edge status
- B.
Inhibits the generation of a TCN
- C.
Goes immediately to a learning state
- D.
Disables itself
- E.
Becomes a normal spanning-tree port
Correct Answer(s)
A. Immediately loses its edge status
E. Becomes a normal spanning-tree portExplanation
When an RSTP edge port receives a BPDU, it immediately loses its edge status and becomes a normal spanning-tree port. This is because the purpose of an edge port is to connect to end devices that do not participate in spanning tree protocol. When a BPDU is received, it indicates the presence of another bridge in the network, so the edge port can no longer be considered as an edge port and must transition to a normal spanning-tree port.Rate this question:
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- 19.
Refer to the exhibit CH5-4 (on flash drive). Server sends an ARP request for the MAC address of its default gateway. If STP is not enabled, what will be the result of this ARP request?
- A.
Router_1 will drop the broadcast and reply with the MAC address of the next hop router.
- B.
Switch_A will reply with the MAC address of the Router_1 E0 interface.
- C.
Switch_A and Switch_B will continuously flood the message onto the network.
- D.
The message will cycle around the network until its TTL is exceeded.
Correct Answer
C. Switch_A and Switch_B will continuously flood the message onto the network.Explanation
If STP (Spanning Tree Protocol) is not enabled, the ARP request sent by the server will not be able to reach the default gateway. Without STP, there will be no loop prevention mechanism in the network. As a result, both Switch_A and Switch_B will continuously flood the ARP request message onto the network, causing it to circulate indefinitely.Rate this question:
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- 20.
Which three statements are accurate regarding RSTP and STP? (Choose three.)
- A.
RSTP uses a faster algorithm to determine root ports.
- B.
RSTP introduced the extended system ID to allow for more than 4096 VLANs.
- C.
Both RSTP and STP use the portfast command to allow ports to immediately transition to forwarding state.
- D.
Like STP PortFast, an RSTP edge port that receives a BPDU loses its edge port status immediately and becomes a normal spanning-tree port.
- E.
Configuration commands to establish primary and secondary root bridges are identical for STP and RSTP.
- F.
Because of the format of the BPDU packet, RSTP is backward compatible with STP.
Correct Answer(s)
C. Both RSTP and STP use the portfast command to allow ports to immediately transition to forwarding state.
E. Configuration commands to establish primary and secondary root bridges are identical for STP and RSTP.
F. Because of the format of the BPDU packet, RSTP is backward compatible with STP.Explanation
RSTP and STP both use the portfast command to allow ports to immediately transition to the forwarding state. The configuration commands to establish primary and secondary root bridges are also identical for both protocols. Additionally, RSTP is backward compatible with STP due to the format of the BPDU packet.Rate this question:
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