CCNA3 Chapter 5 Practice Test Answers
1
Which of the following problems may occur in redundant switched
network topologies? (Choose three)
 Excessive collisions.
 Broadcast storms.
 Multiple frame transmission.
 Fault-tolerance.
 Single point of failure.
 MAC address database instability.
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What is the purpose of the spanning tree algorithm?
To create a redundant topology.
To build correct MAC address tables.
To create a loop-free topology.
To find the shortest path to a network address.
To remove a single point of failure.
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How can a broadcast storm be ended?
Disconnect one of the switches.
Wait until the frames time out.
Send an ICMP source quench message.
Clear the MAC address tables of the switches.
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What is a multiple frame transmission?
A frame is sent to multiple hosts.
Several frames are forwarded by the same switch.
A host receives the same frame several times by different paths.
A frame is received by multiple hosts.
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What is a disadvantage of the spanning tree algorithm?
It takes longer to converge than is desirable.
It is difficult to configure on new switches.
It only works on Cisco catalyst switches.
It turns off some switch ports.
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What is a proposed solution to get rid of this disadvantage?
Build networks with no physical loops.
Avoid sending broadcast messages.
Use rapid spanning tree protocol.
Use spanning tree protocol version two.
Use the Dijkstra algorithm.
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What is a feature of a tree topology?
It has a connection to every node.
Every link is a point-to-point link.
It provides fault-tolerance.
It contains no loops.
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What information is contained in a bridge protocol data unit?
Root BID, route path cost, sender BID, port ID
Root BID, sender BID, default path, bandwidth
Root BID, root path cost, root bridge, designated port
Root bridge, root port, sender BID, designated port
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How is a BID made up?
The switch base MAC followed by a bridge priority, default 1.
The switch base MAC followed by a bridge priority, default 32768.
A bridge priority, default 1, followed by the switch base MAC.
A bridge priority, default 32768, followed by the switch base MAC.
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How do switches choose a root bridge?
They choose the switch with the highest bridge priority.
They choose the switch with the highest BID.
They choose the switch with the lowest BID.
They choose the switch nearest to the default gateway.
They choose the switch nearest to the top of the tree structure.
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What will exist when the spanning tree protocol has worked and the
network has converged?
 One root bridge per network, one root port on each bridge, one
designated port on each bridge, all non-designated ports are blocked.
 One root bridge per network, one root port per non root bridge, one
designated port per segment, non-designated ports.
 One root bridge per segment, one root port per non root bridge, one
designated port per segment, non-designated ports.
 One root bridge per network, one root port on each switch, one nondesignated port on each segment, other ports are blocked.
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units?
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SW
What is the default interval in seconds for sending bridge protocol data
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10
30
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13
What states does a port go through from the time when a switch first
start up to the time when the port is fully operational?
 Blocking, listening, learning, forwarding
 Disabled, listening, learning, forwarding
 Listening, learning, blocking, forwarding
 Blocking, learning, listening, forwarding
 Learning, listening, switching, forwarding
14
Which of the following does a port do in the listening state? (Choose all
that apply.)
 Learning MAC addresses.
 Forwarding user data.
 Receiving BPDUs
 Sending BPDUs
15
Which of the following does a port do in the blocking state? (Choose all
that apply.)
 Learning MAC addresses.
 Forwarding user data.
 Receiving BPDUs
 Sending BPDUs
 None of the above
16
Which of the following does a port do in the learning state? (Choose all
that apply.)
 Learning MAC addresses.
 Forwarding user data.
 Receiving BPDUs
 Sending BPDUs
17
Which is the correct order of the stages carried out by the spanning
tree protocol?
 Select a designated port on each segment, select a root bridge, select
a root port on each non-root bridge, block any remaining (nondesignated) ports
 Select a root port on each switch, select a root bridge, select a
designated port on each segment, block any remaining (nondesignated) ports.
 Select a root bridge, select a designated port on each segment, select
a root port on each non-root bridge, block any remaining (nondesignated) ports
 Select a root bridge, select a root port on each non-root bridge, select a
designated port on each segment, block any remaining (nondesignated) ports.
18
How long can it take for a network using spanning tree topology to
converge again after a topology change?
 up to 2 seconds
 up to 10 seconds
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up to 20 seconds
up to 30 seconds
up to 50 seconds
up to 60 seconds
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What will happen to user data frames while the network is converging?
They will be discarded.
They will be forwarded.
They will be stored until the network has converged.
They will collide.
20
Why might a network administrator change a switch priority to a higher
value than that of other switches in the network?
 To make sure that the switch is chosen as the root bridge.
 To make sure that the switch is not chosen as the root bridge.
 To help the network converge more quickly.
 To make sure that no ports on the switch are blocked.
 To make sure that switch MAC addresses are not used in choosing the
root bridge.
21
In rapid spanning tree protocol, which link types allow ports to move
immediately to forwarding mode?
 Point-to-point
 End to end
 Shared
 Multiple
 Edge type
 Mixed
22
It can take 20 seconds for a port to move from the blocking to the
listening state. What timer controls this interval?
 Blocking timer
 Listening timer
 Spanning tree timer
 Bridge protocol data unit timer
 Max-age timer
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SW
What is the listening forward delay?
The time a port spends in listening mode while the network is
converging.
The time a port spends forwarding mode while the network is
converging.
The time a port spends before it reaches listening mode while the
network is converging.
The time a port spends in listening to a frame before it forwards it.
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24
The server wants to send a message to IP address 192.168.7.5 but it
does not know the MAC address of that host. It sends an ARP request. What
will switch A do with the ARP request?
 Forward it to 192.1687.5.
 Forward it to Switch B
 Forward it through all ports
 Forward it through all ports except the port on which it was received
 Drop it
25
What is the likely effect on the topology shown if Spanning Tree
Protocol has been disabled?
 Excessive collisions
 Broadcast storm
 All hosts will reply to the ARP request
 The router will reply to the ARP request
 The segment 2 port on Switch B will go into blocking mode
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What is the advantage of configuring an access port leading to a PC
with PortFast?
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The STP timers are changed so that the port moves through listening
and learning states more quickly.
The port is secured so that no other PC can be connected to it.
The port will be in the forwarding state as soon as it is enabled.
RSTP will be in use on the switch.
27
Which STP port states are equivalent to the RSTP discarding port
state?
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SW
Blocking, listening and learning
Listening, learning and forwarding
Listening. Learning and disabled
Blocking, listening and disabled
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Which is true of the difference between STP and RSTP?
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STP uses a proposal and agreement process to allow switches to
negotiate on port roles, but RSTP assigns the roles centrally.
STP stops sending user data while the whole network converges, but
RSTP closes down and converges each link separately.
RSTP is able to support VLANs by using Cisco proprietary
enhancements but STP is not.
RSTP is the default version on all Cisco switches now, but STP was
the default until IOS version 11.4
29
How many switches in a network must be running STP or RSTP in
order to avoid broadcast storms?
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30
Which is true of a switch that has spanning tree disabled?
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It will forward all frames in the normal way, and this includes BPDUs,
though it does not originate BPDUs.
It cannot be chosen as the root bridge, and any of its ports that are
involved in loops will be blocked.
If it is in a loop then a broadcast storm is inevitable.
It cannot have any VLAN trunk links.
Which is true of the PVST+ protocol?
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At least one.
At least one in each loop.
At least the switch that is chosen as the root bridge.
All of them.
It is Cisco’s implementation of Rapid STP.
It allows different VLANs to have different root bridges and allows ports
to be blocked for some VLANs but not others.
It supports the use of VLANs and requires that ISL frame tagging
should be used on VLAN trunk links.
It was the first version of STP to include the PortFast feature that
allows access ports to transition directly to the forwarding state.
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Why was the BID modified to include an extra field, and what
information is in this field?
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To allow separate instances of STP to run for each VLAN. The field
contains the VLAN number (VID).
To allow rapid spanning tree protocol to be introduced. The field
contains the value 2.
To allow the PortFast feature to be introduced. The field shows which
ports have been configured as PortFast.
To allow ports to have priorities as well as the switch as a whole having
a priority. The field contains a summary of port priorities.
33
How many missed BPDUs will indicate to a switch running RSTP that a
link has gone down?
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3
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30
34
If a port is configured as a RSTP edge port, what will cause it to revert
to a normal spanning tree port?
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It needs to be manually reconfigured as it cannot revert automatically.
It will revert to a normal spanning tree port if a link in the network goes
down.
It will revert to a normal spanning tree port if it receives a BPDU.
It will revert to a normal spanning tree port if a new election for root
bridge is required.
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In RSTP, a port other than an edge port can transition rapidly to
forwarding state if it is on which type of link?
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SW
Point-to-point
Point-to-multipoint
Shared
Edge-to-edge
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