STP and RSTP

Question 1

What is the primary purpose of STP?
a) To prevent routing loops
b) To prevent switching loops
c) To encrypt network traffic
d) To increase bandwidth

Answer 1

Answer: b) To prevent switching loops

Question 2

Which algorithm does STP use to prevent loops?
a) Dijkstra’s algorithm
b) Bellman-Ford algorithm
c) Spanning Tree Algorithm (STA)
d) Diffie-Hellman algorithm

Answer 2

Answer: c) Spanning Tree Algorithm (STA)

Question 3

What is the default STP mode on Cisco switches?
a) Rapid PVST+
b) MSTP
c) PVST+
d) RSTP

Answer 3

Answer: c) PVST+

Question 4

Which STP state blocks traffic but listens to BPDUs?
a) Blocking
b) Listening
c) Learning
d) Forwarding

Answer 4

Answer: a) Blocking

Question 5

How long does STP take to converge by default?
a) 15 seconds
b) 30 seconds
c) 50 seconds
d) 60 seconds

Answer 5

Answer: c) 50 seconds

Question 6

Which STP state allows MAC address learning but does not forward traffic?
a) Blocking
b) Listening
c) Learning
d) Forwarding

Answer 6

Answer: c) Learning

Question 7

What is the default STP priority value on a Cisco switch?
a) 0
b) 32768
c) 4096
d) 8192

Answer 7

Answer: b) 32768

Question 8

Which STP port state forwards traffic and learns MAC addresses?
a) Blocking
b) Listening
c) Learning
d) Forwarding

Answer 8

Answer: d) Forwarding

Question 9

What is the first step in the STP election process?
a) Elect root ports
b) Elect designated ports
c) Elect the root bridge
d) Block redundant ports

Answer 9

Answer: c) Elect the root bridge

Question 10

Which BPDU field is used to elect the root bridge?
a) Root ID
b) Bridge ID
c) Port ID
d) Max Age

Answer 10

Answer: b) Bridge ID

Question 11

Which STP port role is responsible for forwarding traffic toward the root bridge?
a) Root Port
b) Designated Port
c) Alternate Port
d) Disabled Port

Answer 11

Answer: a) Root Port

Question 12

What is the role of a designated port in STP?
a) Blocks traffic to prevent loops
b) Forwards traffic away from the root bridge
c) Connects to end devices
d) Elects the root bridge

Answer 12

Answer: b) Forwards traffic away from the root bridge

Question 13

Which STP port role is a backup path to a designated port?
a) Root Port
b) Alternate Port
c) Backup Port
d) Disabled Port

Answer 13

Answer: c) Backup Port

Question 14

What happens to a port in the “Listening” state?
a) It discards traffic and ignores BPDUs
b) It forwards traffic and learns MAC addresses
c) It processes BPDUs but does not forward traffic
d) It blocks traffic but listens to BPDUs

Answer 14

Answer: c) It processes BPDUs but does not forward traffic

Question 15

Which STP port state is not part of the original 802.1D standard?
a) Blocking
b) Listening
c) Learning
d) Discarding

Answer 15

Answer: d) Discarding (introduced in RSTP)

Question 16

What is the purpose of the “Disabled” state in STP?
a) Temporarily blocks traffic
b) Administratively shuts down the port
c) Acts as a backup port
d) Elects the root bridge

Answer 16

Answer: b) Administratively shuts down the port

Question 17

Which STP port role is only present in RSTP and not in traditional STP?
a) Root Port
b) Alternate Port
c) Designated Port
d) Backup Port

Answer 17

Answer: b) Alternate Port

Question 18

How does a switch determine the root port?
a) Lowest root path cost
b) Highest bridge ID
c) Fastest link speed
d) Oldest BPDU timestamp

Answer 18

Answer: a) Lowest root path cost

Question 19

What is the default path cost for a 1 Gbps link in STP?
a) 4
b) 19
c) 100
d) 2000

Answer 19

Answer: a) 4

Question 20

Which STP port state comes after “Listening”?
a) Blocking
b) Learning
c) Forwarding
d) Disabled

Answer 20

Answer: b) Learning

Question 21

What is the default Hello timer in STP?
a) 1 second
b) 2 seconds
c) 10 seconds
d) 20 seconds

Answer 21

Answer: b) 2 seconds

Question 22

What is the default Max Age timer in STP?
a) 6 seconds
b) 10 seconds
c) 20 seconds
d) 50 seconds

Answer 22

Answer: c) 20 seconds

Question 23

What happens if a switch does not receive BPDUs within the Max Age time?
a) The switch becomes the root bridge
b) The port transitions to the Listening state
c) The switch recalculates the STP topology
d) The port is disabled

Answer 23

Answer: c) The switch recalculates the STP topology

Question 24

Which BPDU flag indicates a topology change in STP?
a) TC (Topology Change)
b) TCA (Topology Change Acknowledgment)
c) TCN (Topology Change Notification)
d) TCD (Topology Change Detection)

Answer 24

Answer: a) TC (Topology Change)

Question 25

What is the purpose of the Forward Delay timer? a) How long a port stays in Listening/Learning states b) How often BPDUs are sent c) How long before a blocked port becomes active d) How long MAC addresses are retained

Answer 25

Answer: a) How long a port stays in Listening/Learning states

Question 26

What is the default Forward Delay timer in STP? a) 4 seconds b) 15 seconds c) 20 seconds d) 50 seconds

Answer 26

Answer: b) 15 seconds

Question 27

Which BPDU is sent by non-root bridges to inform the root of a topology change? a) Configuration BPDU b) TCN BPDU c) Hello BPDU d) TCA BPDU

Answer 27

Answer: b) TCN BPDU

Question 28

What is the destination MAC address for STP BPDUs? a) 01:80:C2:00:00:00 b) FF:FF:FF:FF:FF:FF c) 00:00:0C:CC:CC:CD d) 01:00:5E:00:00:01

Answer 28

Answer: a) 01:80:C2:00:00:00

Question 29

Which STP timer determines how long BPDUs are stored before aging out? a) Hello Timer b) Forward Delay c) Max Age d) Hold Timer

Answer 29

Answer: c) Max Age

Question 30

What happens if the Hello timer is modified without adjusting other timers? a) Faster convergence b) STP instability c) No effect d) Increased bandwidth

Answer 30

Answer: b) STP instability

Question 31

What is the main improvement of RSTP over STP? a) Faster convergence b) Better encryption c) Higher bandwidth d) More VLAN support

Answer 31

Answer: a) Faster convergence

Question 32

Which IEEE standard defines RSTP? a) 802.1D b) 802.1Q c) 802.1w d) 802.1s

Answer 32

Answer: c) 802.1w

Question 33

How does RSTP achieve faster convergence? a) By eliminating Listening and Learning states b) By using shorter timers c) By introducing new port roles d) Both a and c

Answer 33

Answer: d) Both a and c

Question 34

Which RSTP port role replaces the Blocking state? a) Alternate Port b) Backup Port c) Discarding Port d) Edge Port

Answer 34

Answer: c) Discarding Port

Question 35

What is an "Edge Port" in RSTP? a) A port connected to another switch b) A port connected to an end device c) A disabled port d) A backup root port

Answer 35

Answer: b) A port connected to an end device

Question 36

Which RSTP port role is a backup to the root port? a) Designated Port b) Alternate Port c) Backup Port d) Edge Port

Answer 36

Answer: b) Alternate Por

Question 37

What is the default RSTP convergence time? a) 1-2 seconds b) 5-10 seconds c) 30 seconds d) 50 seconds

Answer 37

Answer: a) 1-2 seconds

Question 38

Which mechanism allows RSTP to confirm a link is operational before forwarding? a) BPDU Guard b) Proposal/Agreement c) Root Guard d) Loop Guard

Answer 38

Answer: b) Proposal/Agreement

Question 39

What happens to an RSTP port if it receives inferior BPDUs? a) It becomes the root port b) It transitions to Discarding c) It ignores them d) It sends a TCN BPDU

Answer 39

Answer: b) It transitions to Discarding

Question 40

Which command enables RSTP on a Cisco switch? a) spanning-tree mode rapid-pvst b) spanning-tree mode rstp c) spanning-tree mode mst d) spanning-tree mode pvst

Answer 40

Answer: a) spanning-tree mode rapid-pvst

Question 41

Which RSTP port state is equivalent to STP’s Blocking state? a) Learning b) Discarding c) Listening d) Forwarding

Answer 41

Answer: b) Discarding

Question 42

In RSTP, what is the role of a Backup Port? a) Backup for the Root Port b) Backup for a Designated Port c) Connects to end hosts d) Used for load balancing

Answer 42

Answer: b) Backup for a Designated Port

Question 43

Which RSTP port type immediately transitions to Forwarding state? a) Root Port b) Edge Port c) Alternate Port d) Designated Port

Answer 43

Answer: b) Edge Port

Question 44

What is the purpose of the Proposal/Agreement mechanism in RSTP? a) Elects the root bridge b) Ensures loop-free topology before forwarding c) Blocks redundant links d) Increases BPDU transmission rate

Answer 44

Answer: b) Ensures loop-free topology before forwarding

Question 45

Which RSTP feature allows switches to synchronize port roles quickly? a) BPDU Filter b) BPDU Guard c) Sync Mechanism d) Root Guard

Answer 45

Answer: c) Sync Mechanism

Question 46

How does RSTP handle topology changes compared to STP? a) Only the root bridge can detect changes b) Any switch can detect and propagate changes c) Changes are ignored unless manually configured d) Uses TCN BPDUs exclusively

Answer 46

Answer: b) Any switch can detect and propagate changes

Question 47

Which command configures a port as an RSTP Edge Port? a) spanning-tree portfast b) spanning-tree edgeport c) spanning-tree bpdufilter enable d) spanning-tree guard root

Answer 47

Answer: a) spanning-tree portfast

Question 48

What happens if an RSTP Edge Port receives a BPDU? a) It becomes a normal STP port b) It remains an Edge Port c) It shuts down d) It ignores the BPDU

Answer 48

Answer: a) It becomes a normal STP port

Question 49

Which RSTP port role is not present in traditional STP? a) Root Port b) Alternate Port c) Designated Port d) Disabled Port

Answer 49

Answer: b) Alternate Port

Question 50

What is the default RSTP bridge priority value? a) 0 b) 32768 c) 4096 d) 8192

Answer 50

Answer: b) 32768

Question 51

Which protocol converges faster, STP or RSTP? a) STP b) RSTP c) Both converge at the same speed d) Depends on network size

Answer 51

Answer: b) RSTP

Question 52

Which of the following is NOT a feature of RSTP? a) Alternate Ports b) Backup Ports c) Listening State d) Edge Ports

Answer 52

Answer: c) Listening State

Question 53

How does RSTP reduce convergence time compared to STP? a) By eliminating the Listening state b) By increasing BPDU timers c) By disabling BPDUs d) By using a different root election process

Answer 53

Answer: a) By eliminating the Listening state

Question 54

Which STP version is backward compatible with 802.1D? a) MSTP b) PVST+ c) RSTP d) Rapid PVST+

Answer 54

Answer: c) RSTP

Question 55

In RSTP, what replaces the TCN BPDU mechanism of STP? a) Topology Change (TC) flags in BPDUs b) Hello BPDUs c) Sync messages d) Proposal/Agreement

Answer 55

Answer: a) Topology Change (TC) flags in BPDUs

Question 56

Which STP version supports per-VLAN spanning trees? a) 802.1D b) 802.1w c) PVST+ d) MSTP

Answer 56

Answer: c) PVST+

Question 57

What is the main drawback of RSTP compared to MSTP? a) Slower convergence b) No VLAN support c) Higher CPU usage in large networks d) No backward compatibility

Answer 57

Answer: c) Higher CPU usage in large networks

Question 58

Which protocol combines multiple VLANs into a single spanning tree instance? a) PVST+ b) Rapid PVST+ c) MSTP d) RSTP

Answer 58

Answer: c) MSTP

Question 59

Which command shows the spanning-tree mode on a Cisco switch? a) show spanning-tree b) show spanning-tree mode c) show spanning-tree summary d) show running-config | include spanning-tree

Answer 59

Answer: a) show spanning-tree

Question 60

Which STP version is recommended for modern networks? a) 802.1D b) RSTP (802.1w) c) PVST+ d) MSTP

Answer 60

Answer: b) RSTP (802.1w)

Question 61

What does BPDU Guard do? a) Blocks unauthorized root bridges b) Disables ports receiving BPDUs c) Filters BPDUs from end devices d) Prevents TCN attacks

Answer 61

Answer: b) Disables ports receiving BPDUs (on Edge Ports)

Question 62

Which feature prevents a switch from becoming the root bridge? a) BPDU Filter b) Root Guard c) Loop Guard d) PortFast

Answer 62

Answer: b) Root Guard

Question 63

What happens if Root Guard detects a superior BPDU? a) The port is blocked b) The switch shuts down c) The port remains forwarding d) The BPDU is ignored

Answer 63

Answer: a) The port is blocked

Question 64

Which command enables BPDU Guard globally? a) spanning-tree bpduguard enable b) spanning-tree portfast bpduguard default c) spanning-tree guard bpdu d) spanning-tree bpdufilter enable

Answer 64

Answer: b) spanning-tree portfast bpduguard default

Question 65

What is the purpose of Loop Guard? a) Prevents root bridge takeover b) Blocks BPDUs on Edge Ports c) Prevents loops due to unidirectional links d) Disables STP on a port

Answer 65

Answer: c) Prevents loops due to unidirectional links

Question 66

Which feature allows a port to skip Listening/Learning states? a) PortFast b) UplinkFast c) BackboneFast d) BPDU Guard

Answer 66

Answer: a) PortFast

Question 67

What does UplinkFast do in STP? a) Speaks up convergence after a root port failure b) Blocks BPDUs on Edge Ports c) Prevents root bridge changes d) Disables STP on uplinks

Answer 67

Answer: a) Speeds up convergence after a root port failure

Question 68

Which Cisco-proprietary STP enhancement is not needed in RSTP? a) PortFast b) UplinkFast c) BPDU Guard d) Root Guard

Answer 68

Answer: b) UplinkFast (RSTP has built-in fast convergence)

Question 69

What is the effect of BPDU Filter on a port? a) Blocks incoming BPDUs b) Prevents the port from sending BPDUs c) Disables STP completely d) Both a and b

Answer 69

Answer: d) Both a and b

Question 70

Which command enables Root Guard on a port? a) spanning-tree rootguard b) spanning-tree guard root c) spanning-tree bpduguard root d) spanning-tree loopguard root

Answer 70

Answer: b) spanning-tree guard root

Question 71

A switch port is stuck in the Blocking state. What could be the issue? a) BPDU Guard is enabled b) The port is an alternate path to the root c) The port is disconnected d) STP is disabled

Answer 71

Answer: b) The port is an alternate path to the root

Question 72

What does a "STP loop" indicate? a) A redundant link is blocked b) BPDUs are not being forwarded c) STP has failed to prevent a loop d) The root bridge is unreachable

Answer 72

Answer: c) STP has failed to prevent a loop

Question 73

How can you verify the root bridge in a network? a) show spanning-tree root b) show spanning-tree c) show cdp neighbors d) show interface trunk

Answer 73

Answer: b) show spanning-tree

Question 74

What causes a topology change in STP? a) A new switch joins b) A link goes down c) A port transitions to Forwarding d) All of the above

Answer 74

Answer: d) All of the above

Question 75

Which command forces a switch to become the root bridge? a) spanning-tree root primary b) spanning-tree vlan 1 priority 0 c) spanning-tree force root d) spanning-tree root force

Answer 75

Answer: a) spanning-tree root primary

Question 76

What happens if two switches have the same bridge priority? a) The switch with the lowest MAC address becomes root b) STP stops working c) Both switches become root d) The switch with the highest IP address wins

Answer 76

Answer: a) The switch with the lowest MAC address becomes root

Question 77

Why would a port be in the "Blocking" state indefinitely? a) It is the root port b) It is a redundant path c) BPDUs are not being received d) It is an Edge Port

Answer 77

Answer: c) BPDUs are not being received

Question 78

How do you disable STP on a Cisco switch? a) no spanning-tree b) spanning-tree disable c) no spanning-tree vlan 1 d) STP cannot be fully disabled

Answer 78

Answer: c) no spanning-tree vlan 1

Question 79

What is the effect of a unidirectional link on STP? a) Faster convergence b) A loop may form c) The root bridge changes d) BPDUs are filtered

Answer 79

Answer: b) A loop may form

Question 80

Which command shows STP port states and roles? a) show spanning-tree brief b) show interface status c) show stp details d) show cdp neighbors

Answer 80

Answer: a) show spanning-tree brief

Question 81

What is the purpose of MSTP (802.1s)? a) Faster convergence than RSTP b) Maps multiple VLANs to a single STP instance c) Replaces PVST+ in Cisco networks d) Both b and c

Answer 81

Answer: d) Both b and c

Question 82

How many STP instances does PVST+ create for 10 VLANs? a) 1 b) 10 c) 20 d) Depends on switch model

Answer 82

Answer: b) 10

Question 83

Which command configures MSTP on a Cisco switch? a) spanning-tree mode mst b) spanning-tree mst enable c) spanning-tree mode rapid-mst d) spanning-tree mst configuration

Answer 83

Answer: a) spanning-tree mode mst

Question 84

What is an MST region? a) A group of switches with the same VLAN-to-instance mapping b) A backup root bridge c) A loop-free segment of the network d) A set of Edge Ports

Answer 84

Answer: a) A group of switches with the same VLAN-to-instance mapping

Question 85

Which STP version is most efficient for large networks with many VLANs? a) PVST+ b) Rapid PVST+ c) MSTP d) RSTP

Answer 85

Answer: c) MSTP

Question 86

What is the default STP mode on modern Cisco switches? a) PVST+ b) Rapid PVST+ c) MSTP d) 802.1D

Answer 86

Answer: b) Rapid PVST+

Question 87

hich command sets a switch as the secondary root bridge? a) spanning-tree root secondary b) spanning-tree vlan 1 priority 4096 c) spanning-tree backup root d) spanning-tree secondary

Answer 87

Answer: a) spanning-tree root secondary

Question 88

What is the range of valid STP priorities? a) 0-65535 b) 0-61440 (in increments of 4096) c) 1-32768 d) 0-32768

Answer 88

Answer: b) 0-61440 (in increments of 4096)

Question 89

Which STP feature prevents a non-root switch from becoming root? a) BPDU Guard b) Root Guard c) Loop Guard d) PortFast

Answer 89

Answer: b) Root Guard

Question 90

What does show spanning-tree vlan 1 display? a) STP status for VLAN 1 b) All VLANs’ STP information c) Root bridge details only d) BPDU statistics

Answer 90

Answer: a) STP status for VLAN 1

Question 91

Which port state is unique to RSTP and not present in traditional 802.1D STP? a) Learning b) Discarding c) Listening d) Forwarding

Answer 91

Answer: b) Discarding

Question 92

What is the destination MAC address for STP BPDUs? a) FF:FF:FF:FF:FF:FF b) 01:80:C2:00:00:00 c) 00:00:0C:CC:CC:CD d) 12:34:56:78:9A:BC

Answer 92

Answer: b) 01:80:C2:00:00:00

Question 93

What is the default STP path cost for a 10 Mbps Ethernet link? a) 2 b) 19 c) 100 d) 2000

Answer 93

Answer: c) 100

Question 93

Which command disables STP on a specific switch port? a) no spanning-tree b) spanning-tree bpdufilter enable c) spanning-tree disable d) no spanning-tree vlan 1

Answer 93

Answer: b) spanning-tree bpdufilter enable

Question 94

Which STP timer is eliminated in RSTP to improve convergence? a) Hello Timer b) Forward Delay c) Max Age d) Hold Timer

Answer 94

Answer: b) Forward Delay (RSTP uses proposal/agreement instead)

Question 95

What does TCN stand for in STP? a) Topology Change Notification b) Trunk Configuration Notice c) Timed Convergence Network d) Transparent Clock Negotiation

Answer 95

Answer: a) Topology Change Notification

Question 96

Which feature prevents Edge Ports from receiving BPDUs? a) BPDU Guard b) Root Guard c) Loop Guard d) PortFast

Answer 96

Answer: a) BPDU Guard

Question 97

What is the valid range for STP bridge priority (in increments of 4096)? a) 0–65535 b) 0–61440 c) 1–32768 d) 0–32768

Answer 97

Answer: b) 0–61440

Question 98

Which command configures a switch port as an RSTP Edge Port? a) spanning-tree edgeport b) spanning-tree portfast c) spanning-tree bpdufilter enable d) spanning-tree guard root

Answer 98

Answer: b) spanning-tree portfast

Question 99

In RSTP, which state replaces the traditional STP "Blocking" state? a) Listening b) Discarding c) Learning d) Forwarding

Answer 99

Answer: b) Discarding

Question 100

A switch port is stuck in "Blocking" state. What is the most likely cause? a) The port is disconnected. b) It is a redundant path to the root bridge. c) BPDU Guard is enabled. d) STP is disabled on the VLAN.

Answer 100

Answer: b) It is a redundant path to the root bridge.

Question 101

What happens if BPDU Guard is enabled on a non-Edge Port? a) The port transitions to Forwarding immediately. b) The port shuts down if it receives a BPDU. c) STP recalculates the topology. d) Nothing—BPDU Guard only works on Edge Ports.

Answer 101

Answer: b) The port shuts down if it receives a BPDU.

Question 102

Which command shows STP inconsistencies (e.g., unidirectional links)? a) show spanning-tree inconsistentports b) show spanning-tree detail c) show stp errors d) show interface status

Answer 102

Answer: a) show spanning-tree inconsistentports

Question 103

Why might a network experience a temporary loop despite STP? a) STP timers are misconfigured. b) A switch is not running STP. c) BPDUs are lost due to a unidirectional link. d) All of the above.

Answer 103

Answer: d) All of the above.

Question 104

How do you manually force a switch to become the root bridge for VLAN 10? a) spanning-tree vlan 10 root primary b) spanning-tree vlan 10 priority 0 c) spanning-tree force-root vlan 10 d) set root vlan 10

Answer 104

Answer: a) spanning-tree vlan 10 root primary

Question 105

What is the key advantage of MSTP over PVST+? a) Faster convergence. b) Supports more VLANs. c) Reduces CPU load by grouping VLANs into instances. d) Backward compatibility with 802.1D.

Answer 105

Answer: c) Reduces CPU load by grouping VLANs into instances.

Question 106

How many MST instances are needed for 100 VLANs if all use the same topology? a) 1 b) 100 c) 256 d) 4096

Answer 106

Answer: a) 1

Question 107

Which command configures an MST region name? a) spanning-tree mst name REGION1 b) spanning-tree mst configuration → name REGION1 c) set stp region REGION1 d) spanning-tree region REGION1

Answer 107

Answer: b) spanning-tree mst configuration → name REGION1

Question 108

Which STP version is Cisco’s default on modern switches? a) PVST+ b) Rapid PVST+ c) MSTP d) 802.1D

Answer 108

Answer: b) Rapid PVST+

Question 109

What is the purpose of the MSTP "revision number"? a) Tracks STP version updates. b) Ensures switches in the same region have identical VLAN mappings. c) Sets the root bridge priority. d) Counts topology changes.

Answer 109

Answer: b) Ensures switches in the same region have identical VLAN mappings.

Question 110

Which protocol combines the benefits of RSTP and per-VLAN spanning trees? a) MSTP b) PVST+ c) Rapid PVST+ d) 802.1D

Answer 110

Answer: c) Rapid PVST+ Explanation: Rapid PVST+ is Cisco’s implementation of RSTP (802.1w) with per-VLAN spanning trees, offering faster convergence than PVST+ while maintaining VLAN-specific topologies.

Question 111

What is the default STP priority value if not manually set? a) 0 b) 32768 c) 4096 d) 8192

Answer 111

Answer: b) 32768 Explanation: The default STP bridge priority is 32768, which can be adjusted in increments of 4096 (e.g., 0, 4096, 8192, etc.).

Question 112

Which STP protection feature disables a port if it receives superior BPDUs? a) BPDU Guard b) Root Guard c) Loop Guard d) PortFast

Answer 112

Answer: b) Root Guard Explanation: Root Guard blocks a port if it receives BPDUs claiming a superior root bridge, preventing unwanted topology changes.

Question 113

What command displays the root bridge for VLAN 1? a) show spanning-tree root b) show spanning-tree vlan 1 c) show stp root d) show spanning-tree summary

Answer 113

Answer: b) show spanning-tree vlan 1 Explanation: This command shows the root bridge ID, root port, and cost for VLAN 1.

Question 114

Which RSTP port role is a backup for the root port? a) Designated Port b) Alternate Port c) Backup Port d) Edge Port

Answer 114

Answer: b) Alternate Port Explanation: The Alternate Port is a backup path to the root bridge (replaces STP’s Blocking state for redundant uplinks).

Question 115

What is the convergence time for RSTP in a failure scenario? a) 1-2 seconds b) 15 seconds c) 30 seconds d) 50 seconds

Answer 115

Answer: a) 1-2 seconds Explanation: RSTP converges in 1-2 seconds (vs. STP’s 30-50 seconds) due to proposal/agreement and port roles.

Question 116

Which BPDU flag indicates a topology change in RSTP? a) TC (Topology Change) b) TCN (Topology Change Notification) c) TCA (Topology Change Acknowledgment) d) TCD (Topology Change Detection)

Answer 116

Answer: a) TC (Topology Change) Explanation: RSTP uses TC flags in BPDUs (not TCN BPDUs like STP) to propagate topology changes.

Question 117

What happens if two switches have the same bridge ID? a) STP stops working b) The switch with the lowest MAC address becomes root c) Both switches become root d) The switch with the highest IP address wins

Answer 117

Answer: b) The switch with the lowest MAC address becomes root Explanation: The MAC address is the tiebreaker when bridge priorities are equal.

Question 118

Which command enables Loop Guard globally? a) spanning-tree loopguard default b) spanning-tree guard loop c) spanning-tree loop-protect d) loopguard enable

Answer 118

Answer: a) spanning-tree loopguard default Explanation: Loop Guard prevents loops caused by unidirectional links by blocking ports that stop receiving BPDUs.

Question 119

What is the STP cost for a 1 Gbps link? a) 4 b) 19 c) 100 d) 2000

Answer 119

Answer: a) 4 Explanation: Modern STP uses these path costs: 10 Mbps: 100 100 Mbps: 19 1 Gbps: 4 10 Gbps: 2