Cisco CCNP Enterprise 350-401 ENCOR Trunking and EtherChannel Troubleshooting Practice Test

 

Topic 06 covers trunking and etherchannel troubleshooting for the Cisco Certified Specialist – Enterprise Core certification. These original practice questions apply the verified 350-401 objectives to practical decisions and troubleshooting. Select one answer unless a fixed number is requested. For broader preparation, visit the Cisco 350-401 ENCOR Exam Dumps page. Each option includes an explanation of the relevant behavior and scenario constraints.

Question 1

Two Cisco switch ports are connected back-to-back. Both are configured with `switchport mode dynamic auto`. `show interfaces trunk` lists neither port, although the physical link is up. Which change most directly forms a negotiated trunk while retaining DTP?

1. Disable DTP with `switchport nonegotiate` on both sides.
2. Change both sides to access mode.
3. Change the native VLAN on one side only.
4. Add the same access VLAN to both ports.
5. Change one side to `switchport mode dynamic desirable`.

Correct Answer: E

 

Correct Answer

Answer E is correct because dynamic desirable actively proposes trunking, while dynamic auto accepts a proposal but does not initiate one.

Incorrect Answers

Answer A is incorrect because disabling negotiation removes the mechanism needed by the current dynamic modes and does not itself force trunking.

Answer B is incorrect because access mode makes both interfaces permanently nontrunking. It does not satisfy the stem’s governing point: Two passive DTP states do not initiate a trunk; at least one side must actively seek or be statically trunking.

Answer C is incorrect because a native VLAN mismatch does not initiate DTP and creates an additional inconsistency.

Answer D is incorrect because an access VLAN does not cause two auto ports to negotiate a trunk.

 

Question 2

A campus interswitch link is configured `switchport mode trunk` on SW1 and `switchport mode dynamic auto` on SW2. The link becomes an operational trunk. Which explanation is correct?

1. Both ports are access ports until user traffic carries two VLANs.
2. Dynamic auto actively initiates trunking regardless of the peer.
3. The native VLAN forces trunking whenever its VLAN number matches.
4. STP elects the trunk side and instructs the other side to follow.
5. SW1 is a trunk; DTP can negotiate the auto peer into trunking.

Correct Answer: E

 

Correct Answer

Answer E is correct because a statically trunking Cisco port can negotiate the neighboring auto port into trunking when DTP is enabled.

Incorrect Answers

Answer A is incorrect because operational trunking is established by configuration/negotiation, not by observing multivlan user traffic.

Answer B is incorrect because dynamic auto is willing to trunk but does not actively propose it to another passive peer.

Answer C is incorrect because native VLAN agreement affects 802.1Q treatment but does not select trunk mode.

Answer D is incorrect because STP controls loop-free forwarding; it does not negotiate switchport trunk mode.

 

Question 3

A Cisco access switch connects to a third-party switch that does not support DTP. The Cisco port is `dynamic auto`; the third-party port is manually configured for 802.1Q tagging. The physical link is up but the Cisco side remains nontrunking. Which correction is most appropriate?

1. Enable PAgP on the Cisco port.
2. Increase the STP path cost on the Cisco port.
3. Set both ports to access VLAN 1.
4. Change the Cisco port to dynamic desirable and rely on the third-party device to answer DTP.
5. Configure the Cisco port as a static trunk and disable DTP negotiation.

Correct Answer: E

 

Correct Answer

Answer E is correct because a peer that cannot speak DTP should use deliberate static trunking; `switchport nonegotiate` avoids sending DTP frames.

Incorrect Answers

Answer A is incorrect because PAgP negotiates EtherChannel, not trunk formation, and does not solve the peer DTP limitation.

Answer B is incorrect because STP cost does not change switchport trunk negotiation.

Answer C is incorrect because that would remove the intended multivlan trunk. It does not satisfy the stem’s governing point: Use a static trunk with negotiation disabled when the peer cannot participate in DTP.

Answer D is incorrect because a device that does not support DTP cannot complete that negotiation.

 

Question 4

Output from one switch shows `Administrative Mode: dynamic desirable` and `Operational Mode: static access` on Gi1/0/12. The cable leads to an endpoint NIC rather than another switch. Which interpretation is best?

1. The discrepancy means the interface is physically down.
2. The output proves the interface configuration was ignored by IOS XE.
3. The port is carrying every VLAN because desirable always means trunk.
4. The port is configured to negotiate but currently operates as access.
5. The endpoint is automatically encapsulating 802.1Q because the switch is desirable.

Correct Answer: D

 

Correct Answer

Answer D is correct because administrative intent and actual negotiated state are separate fields; an endpoint does not establish the DTP trunk.

Incorrect Answers

Answer A is incorrect because administrative and operational switchport modes can differ while the physical link remains up.

Answer B is incorrect because dynamic desirable can legitimately operate nontrunking when the peer does not support or accept trunking.

Answer C is incorrect because desirable actively attempts trunking but does not guarantee an operational trunk with an incapable peer.

Answer E is incorrect because the operational access state indicates the switch is not currently treating the link as a trunk.

 

Question 5

Two distribution switches should always carry VLANs 10, 20, and 30 over a dedicated interswitch link. The design forbids accidental trunk formation on endpoint links and does not need dynamic negotiation. Which configuration approach is most deliberate for this link?

1. Configure both ends dynamic auto.
2. Configure both ends as static trunks and disable DTP negotiation.
3. Enable LACP without configuring switchport mode.
4. Configure both ends as access ports and add three access VLANs.
5. Configure one end dynamic desirable and leave the other at its platform default.

Correct Answer: B

 

Correct Answer

Answer B is correct because the intended role is known in advance, so explicit trunk mode plus no negotiation minimizes dependence on dynamic behavior.

Incorrect Answers

Answer A is incorrect because auto/auto does not actively form a trunk. It does not satisfy the stem’s governing point: Use explicit static trunking when the role is fixed and negotiation is unnecessary.

Answer C is incorrect because LACP addresses link aggregation and does not by itself establish the desired trunking policy.

Answer D is incorrect because an access port belongs to one access VLAN and is not the required multivlan trunk.

Answer E is incorrect because that relies on a dynamic/default state even though the design calls for deliberate static behavior.

 

Question 6

A trunk between SW1 and SW2 is up. VLANs 10 and 20 pass correctly, but hosts in VLAN 30 cannot cross the link. SW1 shows `Vlans allowed on trunk: 10,20` while SW2 shows `10,20,30`. Which first correction addresses the evidence?

1. Enable LACP on the link.
2. Lower the STP priority of SW2.
3. Add VLAN 30 to the allowed list on SW1.
4. Change the native VLAN to 30 on both switches.
5. Remove VLAN 20 from SW2.

Correct Answer: C

 

Correct Answer

Answer C is correct because the local allowed list explicitly excludes the one failing VLAN while the trunk and other VLANs operate.

Incorrect Answers

Answer A is incorrect because the trunk is already up and the failure is VLAN-specific rather than a need for aggregation.

Answer B is incorrect because root election does not add a VLAN to an allowed list.

Answer D is incorrect because native VLAN selection is not required to carry VLAN 30; the explicit allowed-list omission already explains the failure.

Answer E is incorrect because removing a working VLAN does not restore the omitted VLAN 30.

 

Question 7

Gi1/0/1 is an operational trunk and its allowed list includes VLAN 250. `show vlan brief` on the same switch has no VLAN 250, and no VTP mechanism will create it. What best explains why local access ports cannot be placed into VLAN 250 and traffic is not forwarded for it?

1. Any VLAN in an allowed list exists automatically.
2. The native VLAN must always equal the highest allowed VLAN.
3. STP has deleted VLAN 250 because no root was elected.
4. Create and activate VLAN 250 in the local VLAN database.
5. The trunk must be converted to a routed interface for VLAN 250.

Correct Answer: D

 

Correct Answer

Answer D is correct because an allowed list permits an existing VLAN to use the trunk; it does not create the VLAN in the local database.

Incorrect Answers

Answer A is incorrect because the allowed list and VLAN database are separate configuration state.

Answer B is incorrect because native VLAN selection is independent of which VLAN IDs are locally defined.

Answer C is incorrect because STP can control forwarding for a VLAN but does not create or delete the VLAN database entry.

Answer E is incorrect because a routed port would remove Layer 2 trunking rather than create the missing VLAN.

 

Question 8

A trunk connects SW1 and SW2. SW1 uses native VLAN 99; SW2 uses native VLAN 10. CDP reports a native VLAN mismatch. Untagged management frames sent by SW1 should belong to VLAN 99. What is the principal risk?

1. All tagged VLANs stop carrying traffic immediately.
2. LACP necessarily suspends every channel member.
3. The same untagged frame can enter different native VLANs.
4. The switches must elect different STP roots for all VLANs.
5. The physical interface automatically becomes an access port.

Correct Answer: C

 

Correct Answer

Answer C is correct because 802.1Q native traffic can be sent untagged, so disagreement changes the VLAN association applied to the same untagged frame.

Incorrect Answers

Answer A is incorrect because a native mismatch does not inherently disable every tagged VLAN on the trunk.

Answer B is incorrect because the scenario is a trunk mismatch, not evidence of an EtherChannel negotiation failure.

Answer D is incorrect because root election is separate from native-tag classification. It does not satisfy the stem’s governing point: A native VLAN mismatch makes the two ends interpret untagged trunk traffic in different VLAN contexts.

Answer E is incorrect because native VLAN disagreement does not change the operational switchport mode.

 

Question 9

On an 802.1Q trunk with native VLAN 99 and default native-tag behavior, a frame from VLAN 20 and a frame from VLAN 99 leave the trunk. Which TWO statements are correct? Choose TWO.

1. The VLAN 99 frame is normally transmitted untagged as native traffic.
2. Both frames are untagged because trunks do not preserve VLAN identity.
3. The VLAN 20 frame is normally transmitted with an 802.1Q tag identifying VLAN 20.
4. The VLAN 99 frame must be encapsulated in GRE to remain on VLAN 99.
5. The VLAN 20 frame becomes native because its VLAN number is lower than 99.

Correct Answers: A, C

 

Correct Answers

Answer A is correct because by default, traffic whose VLAN matches the native VLAN is sent without an 802.1Q tag.

Answer C is correct because non-native VLAN traffic requires a tag on a conventional 802.1Q trunk so the receiver can recover its VLAN membership.

Incorrect Answers

Answer B is incorrect because trunking exists specifically to carry multiple VLANs and normally tags non-native traffic.

Answer D is incorrect because GRE is unrelated to ordinary 802.1Q native VLAN forwarding.

Answer E is incorrect because native status is explicitly configured, not selected by numeric ordering.

 

Question 10

VLAN 40 works from Access-A to Distribution-A, and from Distribution-B to Access-B. It fails only across the Distribution-A—Distribution-B trunk. That trunk is up; its allowed list is `10,20,30` while every other trunk includes `10,20,30,40`. Which conclusion best localizes the fault?

1. The interdistribution trunk prunes VLAN 40 from the only missing segment.
2. STP must be blocking every VLAN on the interdistribution link.
3. The endpoint default gateways are necessarily wrong.
4. VLAN 40 must be missing from both access-switch databases.
5. The native VLAN must be changed to 40.

Correct Answer: A

 

Correct Answer

Answer A is correct because the path evidence shows VLAN 40 is healthy on both sides and absent exactly where the allowed list omits it.

Incorrect Answers

Answer B is incorrect because other VLANs traverse the same trunk, and the explicit allowed list explains only VLAN 40.

Answer C is incorrect because the failure boundary aligns with a Layer 2 VLAN carriage omission rather than proving a gateway error.

Answer D is incorrect because successful local forwarding on each side contradicts a missing-VLAN explanation there.

Answer E is incorrect because a VLAN need not be native to be carried over a trunk.

 

Question 11

A three-switch path should carry VLANs 100 and 200 end to end. SW1—SW2 is trunking both. SW2 Gi1/0/24 toward SW3 reports `Operational Mode: static access` in VLAN 100. VLAN 100 works to SW3 but VLAN 200 does not. What is the decisive finding?

1. SW1 must be missing VLAN 200 because the far end cannot reach it.
2. The SW2—SW3 hop is an access link and therefore breaks the intended multivlan trunk path.
3. VLAN 200 must be made native on SW1.
4. Enable OSPF between SW2 and SW3.
5. Lower the SW3 bridge priority.

Correct Answer: B

 

Correct Answer

Answer B is correct because the access-mode hop carries one access VLAN and breaks the multivlan trunk requirement exactly where VLAN 200 disappears.

Incorrect Answers

Answer A is incorrect because SW1—SW2 is already confirmed to trunk VLAN 200, so the failure is downstream.

Answer C is incorrect because native status does not compensate for an access-mode hop.

Answer D is incorrect because the requirement is Layer 2 VLAN carriage, not a routed replacement.

Answer E is incorrect because STP root selection does not turn an access port into a trunk.

 

Question 12

All hosts in VLAN 60 and VLAN 70 lose connectivity across an uplink at the same moment. `show interfaces Gi1/0/48` shows line protocol down, and `show interfaces trunk` no longer lists the port. Which diagnosis is better supported than a VLAN-specific configuration error?

1. One access port was assigned to the wrong VLAN.
2. A link/interface failure affects the trunk as a whole.
3. The VLAN 60 STP root changed.
4. Only VLAN 60 was removed from the allowed list.
5. The native VLAN is mismatched for VLAN 70 only.

Correct Answer: B

 

Correct Answer

Answer B is correct because multiple VLANs fail together and the underlying interface is down, which precedes any per-VLAN carriage question.

Incorrect Answers

Answer A is incorrect because an access-port error would not remove the shared uplink from the trunk table for all VLANs.

Answer C is incorrect because a root change does not explain the line protocol down state of the shared uplink.

Answer D is incorrect because that would not explain VLAN 70 failing simultaneously or the physical interface being down.

Answer E is incorrect because a native mismatch does not normally make the physical interface line protocol down.

 

Question 13

SW1 allows VLANs `10,20,30,40` on a trunk. SW2 allows `10,20,30`. Both switches are otherwise correctly configured and VLAN 40 exists on both. Which statement best describes VLAN 40 across this link?

1. Only broadcast frames fail; unicast frames ignore the allowed list.
2. VLAN 40 automatically becomes the native VLAN on SW2.
3. VLAN 40 fails end to end because SW2 does not permit it on the trunk.
4. The trunk converts VLAN 40 into VLAN 30 on SW2.
5. VLAN 40 works normally because one side allows it.

Correct Answer: C

 

Correct Answer

Answer C is correct because a VLAN must be permitted by the relevant trunk processing on both ends for bidirectional Layer 2 service.

Incorrect Answers

Answer A is incorrect because allowed-list enforcement applies to VLAN traffic, not only broadcasts.

Answer B is incorrect because absence from an allowed list does not reclassify a VLAN as native.

Answer D is incorrect because 802.1Q trunking does not renumber an omitted VLAN into a permitted one.

Answer E is incorrect because a one-sided permission cannot make the peer accept and forward the VLAN as intended.

 

Question 14

A trunk is up, but packets believed to be in VLAN 88 appear untagged in a packet capture on one side. The engineer needs to confirm the port native VLAN, administrative mode, operational mode, and negotiation state. Which output is most directly useful?

1. `show ip route`
2. `show clock`
3. `show etherchannel summary`
4. `show processes cpu`
5. `show interfaces <interface> switchport`

Correct Answer: E

 

Correct Answer

Answer E is correct because this output exposes switchport administrative/operational mode and native/access VLAN details needed to interpret the tagging behavior.

Incorrect Answers

Answer A is incorrect because the routing table does not reveal a Layer 2 switchport native VLAN or trunk negotiation state.

Answer B is incorrect because time state is unrelated to VLAN tagging. It does not satisfy the stem’s governing point: Choose switchport verification that directly exposes the tagging and mode parameters under investigation.

Answer C is incorrect because that can show bundle state but is not the primary source for the port native VLAN and switchport operating mode.

Answer D is incorrect because CPU utilization does not identify an 802.1Q tagging configuration.

 

Question 15

A user connects a small managed switch to a wall jack intended only for a single endpoint. The access switch port was left `dynamic desirable`; the user switch supports DTP and becomes a trunk. Which configuration most directly removes this unintended trunking path while preserving the endpoint VLAN?

1. Add every VLAN to the trunk allowed list.
2. Leave desirable mode and change the native VLAN.
3. Configure the wall jack as a static access port in the intended endpoint VLAN.
4. Enable LACP active mode on the wall jack.
5. Lower STP port priority.

Correct Answer: C

 

Correct Answer

Answer C is correct because explicit access mode prevents the endpoint-facing port from negotiating a trunk.

Incorrect Answers

Answer A is incorrect because that would expand rather than eliminate the unintended trunk exposure.

Answer B is incorrect because the port can still negotiate a trunk, so the exposure remains.

Answer D is incorrect because link aggregation does not enforce endpoint access mode and could introduce another negotiation mechanism.

Answer E is incorrect because STP priority affects topology choice, not DTP trunk formation.

 

Question 16

Two switch ports are configured in the same channel group with LACP `passive` mode on both ends. Individual links are up, but no bundle forms. Which correction preserves LACP and requires the fewest changes?

1. Change the native VLAN on one member.
2. Change both sides to PAgP auto.
3. Disable STP.
4. Configure only the port-channel interface as a trunk.
5. Change at least one side to LACP `active`.

Correct Answer: E

 

Correct Answer

Answer E is correct because passive listens for LACP but does not initiate; an active peer initiates negotiation and can form with passive.

Incorrect Answers

Answer A is incorrect because introducing a mismatch can prevent rather than enable bundling.

Answer B is incorrect because auto/auto is also noninitiating and changes the protocol rather than fixing the stated LACP pairing.

Answer C is incorrect because STP is not the cause of a passive/passive LACP negotiation stalemate.

Answer D is incorrect because switchport settings do not make passive/passive LACP peers exchange the negotiation needed to bundle.

 

Question 17

SW1 uses `channel-group 5 mode active` on two links. SW2 uses `channel-group 5 mode desirable`. The links remain individual. What is the key incompatibility?

1. EtherChannel cannot operate on trunk ports.
2. Both sides are passive, so neither initiates.
3. SW1 uses LACP while SW2 uses PAgP, so their channel negotiations are incompatible.
4. Channel-group numbers must be globally identical across all switches.
5. STP permits only one physical link between two switches.

Correct Answer: C

 

Correct Answer

Answer C is correct because active is an LACP mode, whereas desirable is a PAgP mode.

Incorrect Answers

Answer A is incorrect because trunk interfaces can be bundled when member configurations are consistent.

Answer B is incorrect because active and desirable are both initiating modes, but they speak different protocols.

Answer D is incorrect because the local numeric identifier need not match the peer; protocol compatibility and member parameters matter.

Answer E is incorrect because EtherChannel is presented to STP as one logical port when properly formed.

 

Question 18

An interswitch bundle is configured with `channel-group 7 mode on` on both sides. It comes up with no LACP or PAgP neighbors shown. Which statement is correct?

1. PAgP must have silently negotiated the channel.
2. The absence of LACP neighbors proves the bundle is down.
3. The links are statically bundled in mode `on` without LACP or PAgP negotiation.
4. The peer must use passive mode for mode on to work.
5. The port channel can carry only routed traffic.

Correct Answer: C

 

Correct Answer

Answer C is correct because static on mode forces channeling and therefore lacks LACP/PAgP negotiation safeguards.

Incorrect Answers

Answer A is incorrect because mode on does not use PAgP. It does not satisfy the stem’s governing point: Mode on is static aggregation and should not be mistaken for a negotiated LACP/PAgP bundle.

Answer B is incorrect because a static bundle can operate without LACP because it was not configured to use it.

Answer D is incorrect because static on expects a compatible static arrangement, not LACP passive negotiation.

Answer E is incorrect because static versus negotiated aggregation is independent of Layer 2 versus Layer 3 port-channel use.

 

Question 19

A design standard requires LACP. SW1 should initiate negotiation, while SW2 may wait for a peer. Which mode pair is compatible?

1. SW1 auto, SW2 active.
2. SW1 active, SW2 passive.
3. SW1 on, SW2 passive.
4. SW1 passive, SW2 passive.
5. SW1 desirable, SW2 passive.

Correct Answer: B

 

Correct Answer

Answer B is correct because LACP active initiates and passive responds, so this pairing can form the bundle.

Incorrect Answers

Answer A is incorrect because auto is PAgP, not LACP. It does not satisfy the stem’s governing point: A standard LACP initiator/responder pairing is active/passive.

Answer C is incorrect because static on does not negotiate LACP with the passive side.

Answer D is incorrect because neither side initiates LACP in passive/passive. It does not satisfy the stem’s governing point: A standard LACP initiator/responder pairing is active/passive.

Answer E is incorrect because desirable is PAgP and cannot negotiate LACP with a passive peer.

 

Question 20

`show etherchannel summary` displays `Po12(SU)` with Gi1/0/1(P) and Gi1/0/2(s). LACP is configured on both ends. Traffic uses only Gi1/0/1. What does the lowercase `s` member state most strongly indicate for Gi1/0/2?

1. The member is the sole selected forwarding link and Gi1/0/1 is standby.
2. The member is suspended and is not currently participating in forwarding for the port channel.
3. The member is acting as the STP root port outside the channel.
4. The member is carrying only native VLAN traffic.
5. The member is shut down administratively by definition.

Correct Answer: B

 

Correct Answer

Answer B is correct because a suspended member has failed to join the active bundle and should be investigated for negotiation or parameter consistency.

Incorrect Answers

Answer A is incorrect because the P flag marks a member that is bundled in the port channel.

Answer C is incorrect because STP should see the formed EtherChannel as a logical port rather than assign independent forwarding roles to healthy bundled members.

Answer D is incorrect because channel member state is not a per-VLAN forwarding designation.

Answer E is incorrect because suspended is a channel state and does not by itself mean the interface has an explicit shutdown command.

 

Question 21

Three 1-Gb/s interfaces are intended for one LACP EtherChannel. Two operate at 1 Gb/s full duplex; the third was manually forced to 100 Mb/s full duplex. Which finding should be corrected before expecting all three to bundle?

1. The links need separate channel-group numbers.
2. The member speed inconsistency.
3. The port-channel interface needs a different STP root priority.
4. The 1-Gb/s links need different native VLANs.
5. The third member should be set half duplex.

Correct Answer: B

 

Correct Answer

Answer B is correct because EtherChannel members must have compatible interface characteristics; the 100-Mb/s member does not match the other 1-Gb/s members.

Incorrect Answers

Answer A is incorrect because separate groups would defeat the intended single EtherChannel.

Answer C is incorrect because STP topology does not normalize member speeds for channel formation.

Answer D is incorrect because introducing switchport inconsistencies would make bundling less likely.

Answer E is incorrect because that would create an additional incompatibility rather than match the other members.

 

Question 22

Gi1/0/1 and Gi1/0/2 should be members of the same Layer 2 port channel. Gi1/0/1 is a trunk; Gi1/0/2 is configured as an access port in VLAN 20. Why is this a problem?

1. The mismatch matters only to STP, not EtherChannel.
2. Only the access member will carry VLAN 20 and the trunk member will carry all other VLANs.
3. EtherChannel requires every member to be a routed port.
4. The members have inconsistent switchport modes, so they cannot represent one coherent Layer 2 port channel.
5. The access member automatically becomes routed when added to the channel group.

Correct Answer: D

 

Correct Answer

Answer D is correct because a logical port channel needs consistent member Layer 2 behavior rather than mixing access and trunk semantics.

Incorrect Answers

Answer A is incorrect because member configuration consistency is a direct channel-formation requirement.

Answer B is incorrect because the purpose of the bundle is a single logical interface, not independent per-member switchport roles.

Answer C is incorrect because Layer 2 trunk EtherChannels are supported when the members are consistently configured.

Answer E is incorrect because channel membership does not justify an inconsistent access/routed transformation.

 

Question 23

A two-link trunk EtherChannel is intended to use native VLAN 99. Gi1/0/1 is configured with native VLAN 99, but Gi1/0/2 has native VLAN 1. The second member does not join normally. What should be corrected?

1. Use a different LACP system ID on each member.
2. Make the trunk native VLAN consistent across the channel members.
3. Disable VLAN 99 on Gi1/0/1.
4. Make Gi1/0/2 an access port in VLAN 99.
5. Configure a different STP instance for each physical member.

Correct Answer: B

 

Correct Answer

Answer B is correct because native VLAN is part of the Layer 2 trunk configuration that must represent one logical port channel.

Incorrect Answers

Answer A is incorrect because members of a device participate under the device LACP identity; changing identities does not resolve the switchport mismatch.

Answer C is incorrect because removing the intended native VLAN does not establish the required consistent trunk configuration.

Answer D is incorrect because that would introduce a trunk/access mismatch rather than align the members.

Answer E is incorrect because STP should treat the formed port channel as one logical link rather than independently engineer each member.

 

Question 24

A port channel should carry VLANs 10,20,30. Gi1/0/1 has allowed list `10,20,30`; Gi1/0/2 was locally changed to `10,20`. IOS XE reports an inconsistency and the member is suspended. Which remedy is best?

1. Leave the mismatch so VLAN 30 hashes only to Gi1/0/1.
2. Increase VLAN 30 STP cost on Gi1/0/1.
3. Change Gi1/0/2 to PAgP while Gi1/0/1 stays LACP.
4. Make VLAN 30 the native VLAN only on Gi1/0/2.
5. Restore one consistent allowed-VLAN policy for the logical port channel and its members.

Correct Answer: E

 

Correct Answer

Answer E is correct because the bundle should present a single Layer 2 forwarding policy rather than different VLAN carriage on individual members.

Incorrect Answers

Answer A is incorrect because EtherChannel does not use member-specific allowed lists as a traffic-engineering method.

Answer B is incorrect because STP cost cannot validate an inconsistent member trunk configuration.

Answer C is incorrect because mixing negotiation protocols cannot create a coherent bundle.

Answer D is incorrect because that adds another inconsistent parameter and does not align allowed VLAN behavior.

 

Question 25

An engineer changes `switchport trunk allowed vlan` directly on one physical member after the interfaces have already been bundled. The platform warns that VLAN changes should be made on the port-channel interface. Why?

1. Each member is supposed to have a different allowed list for load balancing.
2. The warning means LACP must be disabled before any VLAN change.
3. The port-channel interface exists only for STP and has no switchport configuration.
4. Physical members cannot carry tagged frames after they join a bundle.
5. The port-channel is the logical interface; member-specific overrides can create inconsistency and suspension.

Correct Answer: E

 

Correct Answer

Answer E is correct because post-bundle Layer 2 policy should be applied coherently to the logical port channel so all members represent the same forwarding interface.

Incorrect Answers

Answer A is incorrect because load distribution is based on hashing, not separate VLAN permission lists per member.

Answer B is incorrect because a coherent logical-interface change does not inherently require disabling LACP.

Answer C is incorrect because a Layer 2 port channel carries the logical switchport policy.

Answer D is incorrect because members still transmit the port-channel traffic, including tagged frames, according to the logical configuration.

 

Question 26

`show etherchannel summary` for Po20 displays Gi1/0/1(P), Gi1/0/2(P), and Gi1/0/3(I). Which TWO conclusions are justified? Choose TWO.

1. Gi1/0/1 and Gi1/0/2 are participating in the port channel.
2. All three links contribute to port-channel forwarding capacity.
3. Po20 is necessarily down because one intended member is individual.
4. Gi1/0/3 is operating as an individual/standalone port rather than an active bundled member.
5. Gi1/0/3 must be the STP designated member for the bundle.

Correct Answers: A, D

 

Correct Answers

Answer A is correct because the P flag identifies ports bundled in the channel.

Answer D is correct because the I state means the interface is not participating as a port-channel member.

Incorrect Answers

Answer B is incorrect because the individual member is not part of the active bundle, so its bandwidth cannot be counted as channel capacity.

Answer C is incorrect because a port channel can remain up with a subset of valid bundled members.

Answer E is incorrect because STP views the formed channel logically and the I flag is not an STP role.

 

Question 27

A four-member 1-Gb/s EtherChannel uses a hash based on source/destination IP. One TCP flow between a single source and destination measures about 1 Gb/s even though the aggregate has 4 Gb/s of member capacity. Which explanation is best?

1. A single flow hashes to one member; aggregate capacity comes from multiple independently hashed flows.
2. The port channel should fragment the TCP stream across all links to reach 4 Gb/s.
3. LACP limits every port channel to the speed of one member for all traffic.
4. The trunk native VLAN limits the channel to 1 Gb/s.
5. STP blocks three members because it sees four parallel links.

Correct Answer: A

 

Correct Answer

Answer A is correct because per-flow hashing preserves frame ordering and normally maps a given flow to one physical member.

Incorrect Answers

Answer B is incorrect because ordinary EtherChannel hashing avoids per-packet striping of one flow in order to preserve ordering.

Answer C is incorrect because multiple flows can use different members and consume aggregate capacity.

Answer D is incorrect because native VLAN treatment is unrelated to aggregate member bandwidth.

Answer E is incorrect because STP sees a correctly formed EtherChannel as one logical port.

 

Question 28

A 4×10-Gb/s port channel carries only two very large long-lived flows. Monitoring shows 20 Gb/s on one member and little traffic on two others over a sampled interval. All four members are bundled with no errors. What should the engineer evaluate first?

1. Whether LACP renegotiates every packet to choose the least-used member.
2. Evaluate the hash inputs and flow-key diversity before diagnosing a failed channel member.
3. Whether each member uses a different native VLAN.
4. Whether the port channel needs different channel-group numbers per flow.
5. Whether STP is blocking the underused members independently.

Correct Answer: B

 

Correct Answer

Answer B is correct because a small number of large flows can collide on the same hash result and produce uneven utilization even when every member is healthy.

Incorrect Answers

Answer A is incorrect because LACP forms/maintains the bundle; traffic distribution uses a hash rather than instantaneous per-packet negotiation.

Answer C is incorrect because members should be consistent; different native VLANs are not a load-balancing technique.

Answer D is incorrect because flows are not assigned channel groups; members belong to one logical bundle.

Answer E is incorrect because STP operates on the logical port channel rather than selecting individual healthy members for blocking.

 

Question 29

Po5 consists of four active 10-Gb/s members. The design assumes all four can forward simultaneously. One member fails, while the other three remain bundled and the hash redistributes new traffic. Ignoring protocol overhead, what aggregate member capacity remains?

1. 30 Gb/s.
2. 40 Gb/s.
3. 0 Gb/s because any member failure tears down the whole port channel.
4. 10 Gb/s.
5. 20 Gb/s.

Correct Answer: A

 

Correct Answer

Answer A is correct because three surviving 10-Gb/s members provide 3 × 10 = 30 Gb/s of aggregate member capacity.

Incorrect Answers

Answer B is incorrect because the failed member no longer contributes its 10 Gb/s.

Answer C is incorrect because a properly formed EtherChannel is designed to remain operational with surviving members subject to configured minimum-link constraints, which are not present here.

Answer D is incorrect because that would count only one member rather than the three remaining bundled links.

Answer E is incorrect because only one of four links failed, leaving three rather than two.

 

Question 30

After replacing one member cable, all four LACP members show `(P)` and no errors. Traffic distribution shifts so Gi1/0/4 now carries much more traffic than before, but the port channel remains up and packet loss is absent. Which interpretation is most appropriate?

1. The heavily used member must be suspended.
2. LACP has failed because member utilization is not equal.
3. STP has unbundled the least-used members.
4. The bundle is formed; changed flow hashing/distribution should be evaluated separately from LACP negotiation failure.
5. The only valid fix is to make every flow use all four links packet-by-packet.

Correct Answer: D

 

Correct Answer

Answer D is correct because all members are participating, so utilization balance is a data-distribution question rather than evidence that LACP failed to form the channel.

Incorrect Answers

Answer A is incorrect because the P flag explicitly indicates it is bundled rather than suspended.

Answer B is incorrect because LACP does not guarantee equal byte counts across members; the hash and flow mix govern distribution.

Answer C is incorrect because the summary shows all members participate in one logical link.

Answer E is incorrect because per-packet striping is not the normal EtherChannel model and can create ordering problems.