Topic 07 Practice Test 2 covers Discovery, EtherChannel, and Rapid PVST+ for Cisco Certified Network Associate 200-301 CCNA and maps to objectives 2.3–2.5. For broader exam preparation, review the Cisco CCNA 200-301 Exam Dumps. Every option includes focused technical reasoning explaining both the networking concept and its fit to the scenario.
Question 1
Beacon sees no neighbor information from a newly connected Cisco switch when running `show cdp neighbors`. Which Cisco discovery protocol should be enabled if the design intentionally uses the vendor-specific mechanism? Choose ONE.
- LLDP
- RSTP
- CDP
- LACP
Correct Answer: C
Correct Answer
Answer C is correct because Cisco Discovery Protocol (CDP) is Cisco-proprietary and advertises identity, platform, and port information to directly connected Cisco neighbors. At Beacon, Cisco discovery troubleshooting uses this evidence. The CDP path at Beacon therefore meets the stated constraint. At Beacon, the Cisco discovery state is observable afterward.
Incorrect Answers
Answer A is incorrect because Link Layer Discovery Protocol (LLDP) is an IEEE vendor-neutral discovery protocol and is preferable in multivendor environments, but it is not Cisco’s proprietary mechanism. At Beacon, Cisco discovery troubleshooting uses this evidence. The LLDP path at Beacon therefore misses the stated constraint. At Beacon, the Cisco discovery state is observable afterward.
Answer D is incorrect because Link Aggregation Control Protocol (LACP) negotiates EtherChannel membership and does not perform general neighbor discovery. At Beacon, Cisco discovery troubleshooting uses this evidence. The LACP path at Beacon therefore misses the stated constraint. At Beacon, the Cisco discovery state is observable afterward.
Answer B is incorrect because Rapid Spanning Tree Protocol (RSTP) prevents Layer 2 loops and elects spanning-tree roles; it is not used to inventory adjacent devices. At Beacon, Cisco discovery troubleshooting uses this evidence. The RSTP path at Beacon therefore misses the stated constraint. At Beacon, the Cisco discovery state is observable afterward.
Question 2
Ember’s multivendor link shows no neighbors because only CDP is enabled. Which protocol should be enabled on both sides for vendor-neutral discovery? Choose ONE.
- CDP
- DTP
- LLDP
- PAgP
Correct Answer: C
Correct Answer
Answer C is correct because LLDP is the IEEE 802.1AB standards-based neighbor discovery protocol and is designed to exchange device and port information across vendor boundaries. At Ember, multivendor discovery troubleshooting uses this evidence. The LLDP path at Ember therefore meets the stated constraint. At Ember, the multivendor discovery state is observable afterward.
Incorrect Answers
Answer A is incorrect because CDP is useful between Cisco devices but is Cisco-proprietary, so it is not the standards-based choice required for a multivendor link. At Ember, multivendor discovery troubleshooting uses this evidence. The CDP path at Ember therefore misses the stated constraint. At Ember, the multivendor discovery state is observable afterward.
Answer B is incorrect because Dynamic Trunking Protocol (DTP) negotiates switchport trunking and does not advertise general neighbor inventory information. At Ember, multivendor discovery troubleshooting uses this evidence. The DTP path at Ember therefore misses the stated constraint. At Ember, the multivendor discovery state is observable afterward.
Answer D is incorrect because Port Aggregation Protocol (PAgP) is a Cisco-proprietary EtherChannel negotiation protocol rather than a general discovery protocol. At Ember, multivendor discovery troubleshooting uses this evidence. The PAgP path at Ember therefore misses the stated constraint. At Ember, the multivendor discovery state is observable afterward.
Question 3
Harbor’s `show cdp neighbors` table identifies a device, but the engineer also needs its advertised IP address for remote management. Which command should be used next? Choose ONE.
- show cdp neighbors detail
- show etherchannel summary
- show lldp traffic
- show spanning-tree
Correct Answer: A
Correct Answer
Answer A is correct because `show cdp neighbors detail` expands CDP neighbor information and commonly includes management addressing plus platform, interface, and capability details. At Harbor, CDP detail troubleshooting uses this evidence. The show cdp path at Harbor therefore meets the stated constraint. At Harbor, the CDP detail state is observable afterward.
Incorrect Answers
Answer C is incorrect because `show lldp traffic` focuses on LLDP message counters and does not provide the requested detailed CDP neighbor record. At Harbor, CDP detail troubleshooting uses this evidence. The show lldp path at Harbor therefore misses the stated constraint. At Harbor, the CDP detail state is observable afterward.
Answer B is incorrect because `show etherchannel summary` reports port-channel membership and state, not CDP management addressing for an adjacent device. At Harbor, CDP detail troubleshooting uses this evidence. The show etherchannel path at Harbor therefore misses the stated constraint. At Harbor, the CDP detail state is observable afterward.
Answer D is incorrect because `show spanning-tree` reports spanning-tree topology and port roles rather than detailed device discovery information. At Harbor, CDP detail troubleshooting uses this evidence. The show spanning-tree path at Harbor therefore misses the stated constraint. At Harbor, the CDP detail state is observable afterward.
Question 4
Northstar’s policy forbids Cisco-proprietary PAgP but permits standards-based link aggregation negotiation. Which protocol should the port-channel use? Choose ONE.
- LACP
- DTP
- CDP
- PAgP
Correct Answer: A
Correct Answer
Answer A is correct because LACP is the standards-based Link Aggregation Control Protocol used to negotiate and maintain bundled links in an EtherChannel. At Northstar, LACP standard troubleshooting uses this evidence. The LACP path at Northstar therefore meets the stated constraint. At Northstar, the LACP standard state is observable afterward.
Incorrect Answers
Answer D is incorrect because PAgP can negotiate an EtherChannel on Cisco equipment, but it is Cisco-proprietary and therefore does not meet the standards-based requirement. At Northstar, LACP standard troubleshooting uses this evidence. The PAgP path at Northstar therefore misses the stated constraint. At Northstar, the LACP standard state is observable afterward.
Answer B is incorrect because DTP negotiates Layer 2 trunk mode and is independent of whether parallel links are bundled into an EtherChannel. At Northstar, LACP standard troubleshooting uses this evidence. The DTP path at Northstar therefore misses the stated constraint. At Northstar, the LACP standard state is observable afterward.
Answer C is incorrect because CDP discovers directly connected Cisco devices but does not negotiate aggregate link membership. At Northstar, LACP standard troubleshooting uses this evidence. The CDP path at Northstar therefore misses the stated constraint. At Northstar, the LACP standard state is observable afterward.
Question 5
Quartz finds that one LACP side is active and wants the other side to respond without initiating negotiation. Which channel-group mode should be used? Choose ONE.
- passive on both sides
- active on one side and passive on the other
- auto on one side and desirable on the other
- on on one side and passive on the other
Correct Answer: B
Correct Answer
Answer B is correct because An LACP active interface initiates negotiation, while a passive interface responds; active/passive is therefore a valid LACP pairing. At Quartz, active passive LACP troubleshooting uses this evidence. The active on path at Quartz therefore meets the stated constraint. At Quartz, the active passive LACP state is observable afterward.
Incorrect Answers
Answer A is incorrect because Two passive LACP interfaces wait for the peer to initiate, so negotiation does not begin and the bundle will not form through LACP. At Quartz, active passive LACP troubleshooting uses this evidence. The passive on path at Quartz therefore misses the stated constraint. At Quartz, the active passive LACP state is observable afterward.
Answer C is incorrect because `auto` and `desirable` are PAgP modes, not LACP modes, so that pair does not satisfy an LACP requirement. At Quartz, active passive LACP troubleshooting uses this evidence. The auto on path at Quartz therefore misses the stated constraint. At Quartz, the active passive LACP state is observable afterward.
Answer D is incorrect because Static `on` does not negotiate with LACP; mixing static-on behavior with LACP passive does not create the intended negotiated bundle. At Quartz, active passive LACP troubleshooting uses this evidence. The on on path at Quartz therefore misses the stated constraint. At Quartz, the active passive LACP state is observable afterward.
Question 6
Tundra’s `show etherchannel summary` shows no negotiated LACP channel, and both peer configurations use `mode passive`. What should be changed? Choose ONE.
- Change at least one side to LACP active
- Configure a native VLAN on the port-channel
- Change both sides to PAgP auto
- Enable PortFast on all members
Correct Answer: A
Correct Answer
Answer A is correct because At least one side must be LACP active so negotiation is initiated; the other side may remain passive and respond. At Tundra, passive LACP troubleshooting uses this evidence. The Change at path at Tundra therefore meets the stated constraint. At Tundra, the passive LACP state is observable afterward.
Incorrect Answers
Answer C is incorrect because PAgP auto is a different aggregation protocol and changing both sides to auto would still leave both peers waiting rather than meeting the LACP design. At Tundra, passive LACP troubleshooting uses this evidence. The Change both path at Tundra therefore misses the stated constraint. At Tundra, the passive LACP state is observable afterward.
Answer D is incorrect because PortFast affects spanning-tree behavior and does not cause passive LACP peers to initiate link-aggregation negotiation. At Tundra, passive LACP troubleshooting uses this evidence. The Enable PortFast path at Tundra therefore misses the stated constraint. At Tundra, the passive LACP state is observable afterward.
Answer B is incorrect because A native VLAN may matter on a trunked port-channel but it has no role in starting LACP negotiation between two passive endpoints. At Tundra, passive LACP troubleshooting uses this evidence. The Configure a path at Tundra therefore misses the stated constraint. At Tundra, the passive LACP state is observable afterward.
Question 7
Cobalt sees one interface suspended from an otherwise healthy Layer 2 port-channel. Inspection shows its trunk/access parameters differ from the other members. What is the best action? Choose ONE.
- Configure independent IP addresses on every Layer 2 member
- Assign a different access VLAN to each member for load balancing
- Make the member interface Layer 2 settings consistent with the rest of the bundle
- Give each member a different native VLAN to identify it
Correct Answer: C
Correct Answer
Answer C is correct because EtherChannel members must have compatible Layer 2 characteristics such as switchport mode and VLAN parameters; inconsistent configuration can prevent or suspend bundling. At Cobalt, member consistency troubleshooting uses this evidence. The Make the path at Cobalt therefore meets the stated constraint. At Cobalt, the member consistency state is observable afterward.
Incorrect Answers
Answer D is incorrect because Using different native VLANs on members creates inconsistent trunk behavior and is not a valid way to identify or load-balance EtherChannel links. At Cobalt, member consistency troubleshooting uses this evidence. The Give each path at Cobalt therefore misses the stated constraint. At Cobalt, the member consistency state is observable afterward.
Answer B is incorrect because Different access VLANs on members are incompatible with a single logical Layer 2 port-channel and can prevent the interfaces from joining correctly. At Cobalt, member consistency troubleshooting uses this evidence. The Assign a path at Cobalt therefore misses the stated constraint. At Cobalt, the member consistency state is observable afterward.
Answer A is incorrect because Layer 2 EtherChannel members do not each receive independent routed IP addresses; Layer 3 addressing belongs on the port-channel interface when building a routed channel. At Cobalt, member consistency troubleshooting uses this evidence. The Configure independent path at Cobalt therefore misses the stated constraint. At Cobalt, the member consistency state is observable afterward.
Question 8
Falcon changes an allowed VLAN only on one physical member of Port-channel10 and creates an inconsistency. Which configuration target should be used for the logical trunk policy? Choose ONE.
- The Port-channel interface
- The switch’s management SVI
- Every member with intentionally different VLAN lists
- Only the lowest-numbered physical member
Correct Answer: A
Correct Answer
Answer A is correct because The Port-channel is the logical interface for the bundle, so shared Layer 2 trunk policy should be applied consistently to that logical interface rather than creating member mismatches. At Falcon, logical port-channel troubleshooting uses this evidence. The The Port-channel path at Falcon therefore meets the stated constraint. At Falcon, the logical port-channel state is observable afterward.
Incorrect Answers
Answer D is incorrect because Applying policy only to one physical link can leave the aggregate members inconsistent and does not represent the bundle as one logical link. At Falcon, logical port-channel troubleshooting uses this evidence. The Only the path at Falcon therefore misses the stated constraint. At Falcon, the logical port-channel state is observable afterward.
Answer C is incorrect because Intentionally different VLAN lists defeat member consistency and can prevent correct EtherChannel operation. At Falcon, logical port-channel troubleshooting uses this evidence. The Every member path at Falcon therefore misses the stated constraint. At Falcon, the logical port-channel state is observable afterward.
Answer B is incorrect because An SVI provides Layer 3 service for a VLAN and is unrelated to configuring the trunk behavior of the EtherChannel itself. At Falcon, logical port-channel troubleshooting uses this evidence. The The switch’s path at Falcon therefore misses the stated constraint. At Falcon, the logical port-channel state is observable afterward.
Question 9
Ion’s engineers put separate /31 addresses on each intended physical member and then try to form one routed port-channel. What should they do instead? Choose ONE.
- Configure `no switchport` as appropriate and put the IP address on the Port-channel interface
- Keep the members as access ports and put the IP address on VLAN 1
- Place a different IP address on every physical member
- Use `switchport trunk native vlan` as the Layer 3 address
Correct Answer: A
Correct Answer
Answer A is correct because A routed EtherChannel operates as one logical Layer 3 interface; the port-channel is configured for routed operation and carries the IP address for the aggregate. At Ion, routed EtherChannel troubleshooting uses this evidence. The Configure no path at Ion therefore meets the stated constraint. At Ion, the routed EtherChannel state is observable afterward.
Incorrect Answers
Answer C is incorrect because Independent addresses on physical members treat them as separate Layer 3 links rather than one logical EtherChannel and conflict with the intended aggregate interface. At Ion, routed EtherChannel troubleshooting uses this evidence. The Place a path at Ion therefore misses the stated constraint. At Ion, the routed EtherChannel state is observable afterward.
Answer B is incorrect because An access-port/VLAN 1 design is Layer 2 switching and does not create the requested routed point-to-point port-channel. At Ion, routed EtherChannel troubleshooting uses this evidence. The Keep the path at Ion therefore misses the stated constraint. At Ion, the routed EtherChannel state is observable afterward.
Answer D is incorrect because A native-VLAN command configures 802.1Q trunk behavior and is unrelated to assigning a Layer 3 IP address to a routed EtherChannel. At Ion, routed EtherChannel troubleshooting uses this evidence. The Use switchport path at Ion therefore misses the stated constraint. At Ion, the routed EtherChannel state is observable afterward.
Question 10
Lumen’s port-channel is down and the engineer needs to distinguish bundled members from suspended or stand-alone ports quickly. Which command should be checked first? Choose ONE.
- show interfaces trunk
- show cdp traffic
- show spanning-tree root
- show etherchannel summary
Correct Answer: D
Correct Answer
Answer D is correct because `show etherchannel summary` presents port-channel groups, protocols, logical-channel state, and member-interface flags, making it the direct bundle-verification command. At Lumen, EtherChannel summary troubleshooting uses this evidence. The show etherchannel path at Lumen therefore meets the stated constraint. At Lumen, the EtherChannel summary state is observable afterward.
Incorrect Answers
Answer A is incorrect because `show interfaces trunk` can show a port-channel if it is trunking, but it does not provide the same member-level EtherChannel negotiation and bundling summary. At Lumen, EtherChannel summary troubleshooting uses this evidence. The show interfaces path at Lumen therefore misses the stated constraint. At Lumen, the EtherChannel summary state is observable afterward.
Answer C is incorrect because `show spanning-tree root` focuses on root information and does not identify whether intended physical links are successfully bundled. At Lumen, EtherChannel summary troubleshooting uses this evidence. The show spanning-tree path at Lumen therefore misses the stated constraint. At Lumen, the EtherChannel summary state is observable afterward.
Answer B is incorrect because `show cdp traffic` shows discovery-protocol counters rather than EtherChannel member and port-channel state. At Lumen, EtherChannel summary troubleshooting uses this evidence. The show cdp path at Lumen therefore misses the stated constraint. At Lumen, the EtherChannel summary state is observable afterward.
Question 11
Orchid sees an unexpected switch acting as the VLAN 20 root. Which value should be compared first when diagnosing the election result? Choose ONE.
- The switch with the lowest bridge ID
- The switch with the highest MAC address
- The switch with the greatest root-path cost
- The first switch to boot
Correct Answer: A
Correct Answer
Answer A is correct because Spanning tree elects the root bridge using the lowest bridge ID, which incorporates bridge priority and a MAC-derived component for tie breaking. At Orchid, root election troubleshooting uses this evidence. The The switch path at Orchid therefore meets the stated constraint. At Orchid, the root election state is observable afterward.
Incorrect Answers
Answer B is incorrect because A higher MAC address does not win; when priorities tie, the lower bridge identifier component is favored. At Orchid, root election troubleshooting uses this evidence. The The switch path at Orchid therefore misses the stated constraint. At Orchid, the root election state is observable afterward.
Answer C is incorrect because Root-path cost is used by non-root switches to select paths toward the elected root, not to elect the root bridge itself. At Orchid, root election troubleshooting uses this evidence. The The switch path at Orchid therefore misses the stated constraint. At Orchid, the root election state is observable afterward.
Answer D is incorrect because Boot order does not define the stable root-election rule; bridge ID comparison determines the elected root. At Orchid, root election troubleshooting uses this evidence. The The first path at Orchid therefore misses the stated constraint. At Orchid, the root election state is observable afterward.
Question 12
Redwood changes link speed and notices the switch selects a different upstream interface as root port. Which spanning-tree metric primarily explains that change? Choose ONE.
- Every forwarding port becomes a root port
- The port with the lowest root-path cost toward the root
- The port with the highest interface number
- The port that most recently received a data frame
Correct Answer: B
Correct Answer
Answer B is correct because A non-root switch chooses one root port representing its best path to the root bridge; root-path cost is a primary comparison in that selection process. At Redwood, root-port selection troubleshooting uses this evidence. The The port path at Redwood therefore meets the stated constraint. At Redwood, the root-port selection state is observable afterward.
Incorrect Answers
Answer C is incorrect because Interface numbering is not the fundamental spanning-tree path-selection rule and a higher number does not automatically become the root port. At Redwood, root-port selection troubleshooting uses this evidence. The The port path at Redwood therefore misses the stated constraint. At Redwood, the root-port selection state is observable afterward.
Answer A is incorrect because A switch has one root port per spanning-tree instance, while other forwarding interfaces can be designated ports. At Redwood, root-port selection troubleshooting uses this evidence. The Every forwarding path at Redwood therefore misses the stated constraint. At Redwood, the root-port selection state is observable afterward.
Answer D is incorrect because User data arrival timing does not determine the root-port election; BPDUs and spanning-tree path information do. At Redwood, root-port selection troubleshooting uses this evidence. The The port path at Redwood therefore misses the stated constraint. At Redwood, the root-port selection state is observable afterward.
Question 13
Aster observes one forwarding port selected on a shared segment while the competing port is not designated. What is the role of the winning segment-facing port? Choose ONE.
- Alternate port
- Disabled port
- Designated port
- Root port
Correct Answer: C
Correct Answer
Answer C is correct because The designated port is elected for a Layer 2 segment and represents the best path from that segment toward the root; it normally forwards for that segment. At Aster, designated-port role troubleshooting uses this evidence. The Designated port path at Aster therefore meets the stated constraint. At Aster, the designated-port role state is observable afterward.
Incorrect Answers
Answer D is incorrect because The root port is selected on each non-root bridge as that switch’s best path to the root, which is a different role from the per-segment designated port. At Aster, designated-port role troubleshooting uses this evidence. The Root port path at Aster therefore misses the stated constraint. At Aster, the designated-port role state is observable afterward.
Answer A is incorrect because An alternate port provides a redundant path and normally remains in a discarding role rather than serving as the segment’s forwarding designated port. At Aster, designated-port role troubleshooting uses this evidence. The Alternate port path at Aster therefore misses the stated constraint. At Aster, the designated-port role state is observable afterward.
Answer B is incorrect because A disabled port does not participate in spanning-tree forwarding or election for the segment. At Aster, designated-port role troubleshooting uses this evidence. The Disabled port path at Aster therefore misses the stated constraint. At Aster, the designated-port role state is observable afterward.
Question 14
Delta loses the active root path and a previously discarding redundant port rapidly takes over. Which role did that backup port have before the failure? Choose ONE.
- Designated port
- Edge port only
- Alternate port
- Root port on the root bridge
Correct Answer: C
Correct Answer
Answer C is correct because An alternate port provides a redundant path toward the root and normally remains discarding until it is needed, enabling faster convergence when the active path fails. At Delta, alternate-port role troubleshooting uses this evidence. The Alternate port path at Delta therefore meets the stated constraint. At Delta, the alternate-port role state is observable afterward.
Incorrect Answers
Answer A is incorrect because A designated port is the selected forwarding port for a segment and is not the normal description of the blocked backup path in this scenario. At Delta, alternate-port role troubleshooting uses this evidence. The Designated port path at Delta therefore misses the stated constraint. At Delta, the alternate-port role state is observable afterward.
Answer B is incorrect because Edge/PortFast status describes an endpoint-facing convergence behavior and is not the spanning-tree role for a redundant infrastructure path. At Delta, alternate-port role troubleshooting uses this evidence. The Edge port path at Delta therefore misses the stated constraint. At Delta, the alternate-port role state is observable afterward.
Answer D is incorrect because The root bridge has no root port because it is the destination of root paths; therefore this cannot describe the redundant port shown. At Delta, alternate-port role troubleshooting uses this evidence. The Root port path at Delta therefore misses the stated constraint. At Delta, the alternate-port role state is observable afterward.
Question 15
Granite migrates from classic 802.1D terminology and wants the simplified Rapid STP state model. Which set should appear in the documentation? Choose ONE.
- Down, testing, standby
- Blocking, listening, learning, forwarding, disabled
- Active, passive, on
- Discarding, learning, forwarding
Correct Answer: D
Correct Answer
Answer D is correct because Rapid STP consolidates non-forwarding behavior into discarding and uses the operational states discarding, learning, and forwarding. At Granite, RSTP states troubleshooting uses this evidence. The Discarding, learning, path at Granite therefore meets the stated constraint. At Granite, the RSTP states state is observable afterward.
Incorrect Answers
Answer B is incorrect because The five-state blocking/listening/learning/forwarding/disabled model is associated with classic 802.1D terminology rather than the simplified Rapid STP state set. At Granite, RSTP states troubleshooting uses this evidence. The Blocking, listening, path at Granite therefore misses the stated constraint. At Granite, the RSTP states state is observable afterward.
Answer C is incorrect because Active, passive, and on are link-aggregation negotiation/configuration terms, not Rapid PVST+ port states. At Granite, RSTP states troubleshooting uses this evidence. The Active, passive, path at Granite therefore misses the stated constraint. At Granite, the RSTP states state is observable afterward.
Answer A is incorrect because Down, testing, and standby are not the standardized Rapid STP forwarding-state names used to describe convergence. At Granite, RSTP states troubleshooting uses this evidence. The Down, testing, path at Granite therefore misses the stated constraint. At Granite, the RSTP states state is observable afterward.
Question 16
Juniper users experience unnecessary startup delay on confirmed endpoint-only access ports. Which Rapid PVST+ edge feature should be enabled where no switch is expected? Choose ONE.
- PortFast
- LACP passive
- Loop Guard
- Root Guard
Correct Answer: A
Correct Answer
Answer A is correct because PortFast treats an interface as an edge port and allows it to transition rapidly to forwarding, which is appropriate for ports known to connect only to endpoints. At Juniper, PortFast edge troubleshooting uses this evidence. The PortFast path at Juniper therefore meets the stated constraint. At Juniper, the PortFast edge state is observable afterward.
Incorrect Answers
Answer D is incorrect because Root Guard protects root placement by blocking a port that receives superior BPDUs; it does not primarily accelerate endpoint-port forwarding. At Juniper, PortFast edge troubleshooting uses this evidence. The Root Guard path at Juniper therefore misses the stated constraint. At Juniper, the PortFast edge state is observable afterward.
Answer C is incorrect because Loop Guard protects against certain unidirectional or missing-BPDU conditions on non-designated paths and is not the edge-port acceleration feature. At Juniper, PortFast edge troubleshooting uses this evidence. The Loop Guard path at Juniper therefore misses the stated constraint. At Juniper, the PortFast edge state is observable afterward.
Answer B is incorrect because LACP passive is an EtherChannel negotiation mode and has no role in Rapid PVST+ edge-port convergence. At Juniper, PortFast edge troubleshooting uses this evidence. The LACP passive path at Juniper therefore misses the stated constraint. At Juniper, the PortFast edge state is observable afterward.
Question 17
Mesa’s endpoint port enters err-disabled immediately after someone connects an unmanaged switch that sends a BPDU. Which spanning-tree protection most likely caused that deliberate action? Choose ONE.
- Loop Guard
- Root Guard
- BPDU Filter
- BPDU Guard
Correct Answer: D
Correct Answer
Answer D is correct because BPDU Guard protects edge/PortFast ports by placing the interface into an error-disabled condition when BPDUs are received, preventing an unexpected switch from joining the topology. At Mesa, BPDU Guard troubleshooting uses this evidence. The BPDU Guard path at Mesa therefore meets the stated constraint. At Mesa, the BPDU Guard state is observable afterward.
Incorrect Answers
Answer C is incorrect because BPDU Filter suppresses or filters BPDU transmission/reception depending on how it is configured; it is not the same fail-closed BPDU-reception behavior described. At Mesa, BPDU Guard troubleshooting uses this evidence. The BPDU Filter path at Mesa therefore misses the stated constraint. At Mesa, the BPDU Guard state is observable afterward.
Answer B is incorrect because Root Guard puts a port into root-inconsistent when superior BPDUs threaten root placement, rather than generally err-disabling an edge port on any BPDU. At Mesa, BPDU Guard troubleshooting uses this evidence. The Root Guard path at Mesa therefore misses the stated constraint. At Mesa, the BPDU Guard state is observable afterward.
Answer A is incorrect because Loop Guard protects against a blocked/root path incorrectly transitioning because expected BPDUs stop arriving, not against a new switch sending a BPDU on an edge port. At Mesa, BPDU Guard troubleshooting uses this evidence. The Loop Guard path at Mesa therefore misses the stated constraint. At Mesa, the BPDU Guard state is observable afterward.
Question 18
Pioneer sees a customer-facing port move to root-inconsistent after the customer switch begins advertising superior BPDUs. Which feature is working as designed? Choose ONE.
- Loop Guard
- Root Guard
- BPDU Guard
- PortFast
Correct Answer: B
Correct Answer
Answer B is correct because Root Guard allows normal spanning-tree participation but places the port in root-inconsistent if superior BPDUs would cause that port to become a path toward an unauthorized root. At Pioneer, Root Guard troubleshooting uses this evidence. The Root Guard path at Pioneer therefore meets the stated constraint. At Pioneer, the Root Guard state is observable afterward.
Incorrect Answers
Answer C is incorrect because BPDU Guard is normally used to protect edge ports and reacts to BPDU receipt by err-disabling the interface rather than enforcing root placement on a downstream switch link. At Pioneer, Root Guard troubleshooting uses this evidence. The BPDU Guard path at Pioneer therefore misses the stated constraint. At Pioneer, the Root Guard state is observable afterward.
Answer A is incorrect because Loop Guard protects against loss of expected BPDUs on alternate/root paths; it is not designed to reject a downstream device that advertises a superior root. At Pioneer, Root Guard troubleshooting uses this evidence. The Loop Guard path at Pioneer therefore misses the stated constraint. At Pioneer, the Root Guard state is observable afterward.
Answer D is incorrect because PortFast accelerates edge-port forwarding and should not be used as the mechanism for preventing a downstream switch from becoming root. At Pioneer, Root Guard troubleshooting uses this evidence. The PortFast path at Pioneer therefore misses the stated constraint. At Pioneer, the Root Guard state is observable afterward.
Question 19
Summit’s blocked redundant port becomes loop-inconsistent after expected BPDUs disappear. Which protection feature is responsible? Choose ONE.
- PortFast
- BPDU Guard
- Root Guard
- Loop Guard
Correct Answer: D
Correct Answer
Answer D is correct because Loop Guard monitors ports that should continue receiving BPDUs and can place them into a loop-inconsistent state rather than allowing an unsafe forwarding transition when BPDUs disappear. At Summit, Loop Guard troubleshooting uses this evidence. The Loop Guard path at Summit therefore meets the stated constraint. At Summit, the Loop Guard state is observable afterward.
Incorrect Answers
Answer C is incorrect because Root Guard reacts to superior BPDUs that threaten root placement, which is a different failure condition from losing expected BPDUs on a redundant path. At Summit, Loop Guard troubleshooting uses this evidence. The Root Guard path at Summit therefore misses the stated constraint. At Summit, the Loop Guard state is observable afterward.
Answer B is incorrect because BPDU Guard is commonly applied to edge ports and reacts when BPDUs are received, the opposite trigger from the missing-BPDU condition described. At Summit, Loop Guard troubleshooting uses this evidence. The BPDU Guard path at Summit therefore misses the stated constraint. At Summit, the Loop Guard state is observable afterward.
Answer A is incorrect because PortFast accelerates edge convergence and does not provide the missing-BPDU protection required for an infrastructure redundancy path. At Summit, Loop Guard troubleshooting uses this evidence. The PortFast path at Summit therefore misses the stated constraint. At Summit, the Loop Guard state is observable afterward.
Question 20
Beacon finds BPDUs intentionally filtered on an infrastructure port and is concerned the neighboring switches can no longer exchange spanning-tree information. Why is this dangerous? Choose ONE.
- It forces the local switch to become the root on every VLAN
- It automatically forms an EtherChannel with the neighbor
- Suppressing BPDUs can hide topology information and permit a Layer 2 loop
- It encrypts BPDUs and breaks CDP only
Correct Answer: C
Correct Answer
Answer C is correct because Spanning tree depends on BPDU exchange to calculate a loop-free topology; suppressing BPDUs on infrastructure links can hide redundant paths and allow forwarding loops. At Beacon, BPDU Filter troubleshooting uses this evidence. The Suppressing BPDUs path at Beacon therefore meets the stated constraint. At Beacon, the BPDU Filter state is observable afterward.
Incorrect Answers
Answer A is incorrect because BPDU filtering does not deterministically force a switch to become root; root election still depends on bridge information seen by participating devices. At Beacon, BPDU Filter troubleshooting uses this evidence. The It forces path at Beacon therefore misses the stated constraint. At Beacon, the BPDU Filter state is observable afterward.
Answer B is incorrect because BPDU Filter has no EtherChannel negotiation function and cannot form a link-aggregation bundle. At Beacon, BPDU Filter troubleshooting uses this evidence. The It automatically path at Beacon therefore misses the stated constraint. At Beacon, the BPDU Filter state is observable afterward.
Answer D is incorrect because BPDU filtering concerns spanning-tree control messages; it does not encrypt BPDUs or operate as a CDP-specific security mechanism. At Beacon, BPDU Filter troubleshooting uses this evidence. The It encrypts path at Beacon therefore misses the stated constraint. At Beacon, the BPDU Filter state is observable afterward.
