CCNA 3 Module 7 V3.1 Answers

1. Which of the following describe the BIDs used in a spanning tree topology? (Choose two.)

They are sent out by the root bridge only after the inferior BPDUs are sent.

They consist of a bridge priority and MAC address.

Only the root bridge will send out a BID.

They are used by the switches in a spanning tree topology to elect the root bridge.

The switch with the fastest processor will have the lowest BID.


2. Which algorithm is used to create a loop free switched topology?

Spanning Tree

Shortest Path First


Rapid Tree



3. What is meant by "five nines" network uptime?

A network should be available until 9:00 pm five days of the week.

A network should be functioning 99.999% of the time.

There should be five nine-port uplinks for each backbone segment.

Five percent of network expenditures should address 99% of user requirements.

Nothing short of 100% network uptime is acceptable in modern networks.



CCNA 3 Module 7 V3.1 Answers (1)
Switch_A and Switch_B shown in the graphic receive an ARP request from the host and forward it out their ports. The switches receive the forwarded requests from each other and in turn flood the requests again. What will be the result if this process continues?

a broadcast storm

multicast errors

ARP table errors

MAC address instability

redundant unicast frame forwarding


5. Which of the following are valid STP port states? (Choose three.)







6. How often are BPDUs sent by default in a network using the spanning-tree algorithm?

every second

every two seconds

every three seconds

every four seconds


7. What happens when there is a topology change on a network that utilizes STP ? (Choose two.)

User traffic is disrupted until recalculation is complete.

The switch recomputes the Spanning Tree topology after the network converges.

All ports are placed in learning state until convergence has occurred.

A delay of up to 50 seconds is incurred for convergence of the new Spanning Tree topology.

User data is forwarded while BPDUs are exchanged to recompute the topology.


8. How can a network administrator influence which STP switch becomes the root bridge?

Configure the switch as the static root bridge.

Change the BPDU to a higher value than that of the other switches in the network.

Change the BPDU to a lower value than that of the other switches in the network.

Set the switch priority to a smaller value than that of the other switches in the network.

Set the switch priority to a higher value than that of the other switches in the network.


9. What features of the Spanning-Tree Protocol contribute to the time it takes for a switched network to converge after a topology change occurs? (Choose three.)

the max-age timer

the listening forward delay

the spanning-tree hold down timer

the learning forward delay

the spanning-tree path cost

the blocking delay


10. How does a switch forward a multicast frame through the network?

It floods it to all ports as a broadcast.

It is forwarded only to ports that contain the destination address.

It is sent to the port that contains the first destination address.

It floods it to all ports except the one it was received on.

It is dropped and not sent to any address.


11. Following a link failure, when does Rapid Spanning Tree Protocol allow point-to-point and edge type links to go to the forwarding state?

in 15 seconds



in 30 seconds

after 90 seconds


12. What is the first step in the process of convergence in a spanning tree topology?

election of the root bridge

determination of the designated port for each segment

blocking of the non-designated ports

selection of the designated trunk port

activation of the root port for each segment


13. What link types have been defined for Rapid Spanning-Tree Protocol? (Choose three.)








14. What characteristic of Ethernet makes a redundantly switched network prone to loops?

Routers are only able to prevent loops at Layer 3, while Ethernet exists at Layer 2.

The Ethernet protocol has no TTL mechanism.

Switches lack the sophisticated software required to prevent loops.

Looping of frames is a reliability mechanism built in to the Ethernet protocol.


15. In which STP state does a switch port transmit user data and learn MAC addresses?







16. In which STP state does a port record MAC addresses but not forward user data?







17. Which of the following criteria does a switch use to select the root bridge? (Choose two.)

memory size

bridge priority

switching speed

number of ports

base MAC address

switch location


18. What elements will exist in a converged network with one spanning tree? (Choose two.)

one root bridge per network

all non-designated ports forwarding

one root port per non-root bridge

multiple designated ports per segment

one designated port per network



CCNA 3 Module 7 V3.1 Answers (2)
Refer to the network shown in the graphic. Host1 needs to transfer data to host2, but host1 has no MAC address entry in its ARP cache for host2. What will happen on the network as host1 prepares to transmit its data to host2?

Host1 will receive an ICMP destination unknown message from switch3.

All hosts in the network shown will receive an ARP request message from host1.

Multicasting will occur until host2 is located.

Switch3 will send the host2 MAC address from its bridging table to host1.

A broadcast storm will occur.


20. How much time does it take for a switch port to go from the blocking state to the forwarding state?

2 seconds

15 seconds

20 seconds

50 seconds


CCNA 3 Module 7 V3.1 Answers (3)
Refer to the graphic. 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?

Router_1 will kill the broadcast and reply with the MAC address of the next hop router.

Switch_A will reply with the MAC address of the Router_1 E0 interface.

Switch_A and Switch_B will continuously flood the message onto the network.

Switch_B will broadcast the request and reply with the Router_1 address.

The message will cycle around the network until its TTL is exceeded.


22. Which of the following are problems that can occur in redundantly switched networks? (Choose three.)

broadcast storms

corrupted ARP tables

duplicate MAC addresses

inaccurate routing tables

multiple copies of Ethernet frames

MAC address table instability


23. How is the information contained in BPDUs used by switches? (Choose two.)

to prevent loops by sharing bridging tables between connected switches

to set the duplex mode of a redundant link

to determine the shortest path to the root bridge

to determine which ports will forward frames as part of the spanning tree

to activate looped paths throughout the network

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