Cisco Certified Network Associate (CCNA) 200-301 Practice Test 21
Question 200
A switching team must implement a change. A Port-channel contains three active member links and should remain usable after one fails, if min-links constraints permit. Which technical decision most directly meets these requirements?
- Shut down the entire Port-channel whenever any one of three members fails regardless of min-links.
- Expect full original aggregate physical capacity even after one of three equal-speed links fails.
- Route around the failed member using OSPF LSAs for each internal EtherChannel physical link.
- Keep the Port-channel logically up using its remaining two eligible bundled members, subject to any configured `min-links` minimum.
Explanation
Correct Answer
D:EtherChannel abstracts multiple active links into one logical interface. When a member fails, surviving compatible active members continue forwarding with less aggregate bandwidth unless policy requires more links.
Incorrect Answers
A:Ordinary bundles survive a single member loss if enough active links remain.
B:Removing an active member normally lowers available aggregate capacity; hash distribution remains among survivors.
C:The logical Layer 2 bundle hides individual member failures from an IP-routing topology in this design.
Question 201
On a two-link EtherChannel, Cisco Switch A and Switch B both configure `channel-group 5 mode passive`. The interfaces and VLAN settings match and are physically up, but neither side bundles and the LACP neighbor table remains empty. Which change directly addresses the negotiation deadlock?
- Change both sides to PAgP `auto` so a passive pair sends LACP frames.
- Add a third physical link because LACP cannot start with only two members.
- Set at least one side's member interfaces to LACP `active`, keeping the other side `passive` or `active`.
- Configure the EtherChannel load-balance algorithm to use the destination MAC, without changing negotiation modes.
Explanation
Correct Answer
C:LACP `passive` listens for LACP negotiations but does not initiate them. When both peers use passive, neither begins the protocol exchange, so no LACP partner state or bundled member is established despite matching physical links. Configure one or both peers in `active` mode. Keep compatible channel groups, speed/duplex and Layer 2 settings, then verify with `show lacp neighbor` and `show etherchannel summary` that both ports are selected into an operational logical bundle. This is an initiation failure, distinct from a hash-distribution issue that can occur after a bundle forms.
Incorrect Answers
A:PAgP `auto` is a passive setting of Cisco's Port Aggregation Protocol, not LACP. Changing both peers from LACP passive to PAgP auto would not create an actively negotiating LACP pair, and an auto/auto PAgP combination is not the needed solution. Use LACP active/passive or active/active compatibility.
B:An EtherChannel may form with one or more valid members subject to platform and configuration limits; LACP does not inherently require a third cable to initiate. The two existing physical links already satisfy the intended basic aggregation count. The missing protocol initiation is caused by both ports being passive, not insufficient cabling.
D:A load-balancing algorithm chooses which operational member carries a flow after the logical channel has formed. It cannot initiate LACP PDUs or populate an empty LACP neighbor table. The observed failure occurs before hashing can distribute frames. Correct the LACP active/passive negotiation state first.
Question 202
One bundle member reports a different configured speed and shows suspended while the other members forward as a Port-channel. The team should investigate which specific technical cause?
- All differing-speed links must be bundled automatically because LACP disregards all physical attributes.
- The member speed mismatch violates EtherChannel compatibility, so the inconsistent port is suspended instead of being bundled.
- The Port-channel is absent from the routing table because all other physical members are down.
- An incorrect PC DNS suffix forces the switch to mark the Ethernet member suspended.
Explanation
Correct Answer
B:Members of a Port-channel need compatible Layer 1/2 attributes, including speed and duplex where required. Reconcile the member configuration and inspect `show etherchannel summary` flags.
Incorrect Answers
A:LACP does not override compatibility checks; an incompatible link can be suspended.
C:The scenario states other bundled members still forward; the individual member inconsistency is observed.
D:DNS is an IP name service and cannot explain the observed Ethernet bundle compatibility flag.
Question 203
A switching team must explain an outage. The Port-channel trunk permits VLAN 20, but one member has incompatible access-port configuration and remains unbundled. Which diagnosis follows from these observations?
- The member is successfully bundled because the logical interface allows VLAN 20, regardless of local member mode.
- The physical member is configured as an access port rather than compatible trunk member, preventing it from joining the Port-channel.
- The only explanation is a missing IPv4 host default gateway, despite the member being unbundled at Layer 2.
- Changing the router OSPF network type automatically corrects access/trunk settings of the channel member.
Explanation
Correct Answer
B:Channel members must agree on the link’s Layer 2 switchport properties and be compatible with the logical Port-channel. A trunk carrying VLAN 20 cannot accept an inconsistent access-only member.
Incorrect Answers
A:A logical Port-channel allowed list does not ignore incompatible physical membership configuration.
C:IP default gateway selection is downstream of the observed LACP or local member eligibility failure.
D:OSPF has no role in the switchport mode consistency checks for a Layer 2 bundle.
Question 204
A switching team collects this evidence: The bundle is present at Layer 2, but the IP address is configured on one physical member and no routed Port-channel address exists. Which root-cause interpretation best fits the observations?
- Keep the Port-channel as an ordinary VLAN trunk and expect member IP addresses to become the routed Port-channel IP.
- Add an LACP timer change and leave the Port-channel without a Layer 3 address.
- Change the trunk native VLAN to the same numerical value as the desired IPv4 subnet prefix.
- The aggregate is not configured as a routed Port-channel; move the L3 configuration to `interface Port-channel` with `no switchport` and proper IP addressing.
Explanation
Correct Answer
D:A Layer 3 EtherChannel presents one logical routed interface. Numbering a single physical member while leaving the Port-channel at Layer 2 does not establish the intended neighbor subnet on the aggregate.
Incorrect Answers
A:Layer 2 Port-channel membership does not automatically inherit an individual member’s IPv4 address.
B:Faster LACP exchanges do not establish the missing routed interface/gateway configuration.
C:A VLAN ID is not an IP prefix and does not create a numbered Layer 3 port-channel.
Question 205
A branch switch connects two GigabitEthernet links to a non-Cisco switch. The remote switch is running IEEE 802.3ad LACP active, but the Cisco operator configured `channel-group 7 mode desirable` and the links remain individual. Both interfaces are physically up with matching speed and VLAN settings. Which cause best explains why no standards-based bundle forms?
- The LACP system IDs disagree although both peers use LACP active.
- Both peers use LACP passive and neither sends negotiation frames.
- The port-channel is active but a single TCP session hashes to one member.
- The Cisco side is using PAgP while the other side expects LACP.
Explanation
Correct Answer
D:The Cisco `desirable` mode initiates Port Aggregation Protocol (PAgP), whereas the third-party switch's `active` mode initiates Link Aggregation Control Protocol (LACP). They are different negotiation protocols and do not create a common bundle merely because each side is willing to negotiate. Cisco documents LACP `active` and `passive`; at least one side must be active for a passive counterpart. Configure compatible LACP modes on the Cisco interface members, keep physical and switchport properties consistent, and verify protocol and bundled-member flags with `show etherchannel summary` and `show lacp neighbor`.
Incorrect Answers
A:A disagreement about LACP partner identification would be investigated only after confirming that both devices actually send and receive LACP protocol data units. The Cisco mode `desirable` is a PAgP negotiating mode, not an LACP mode, so the premise that both peers use LACP active is false here. Matching physical speed and allowed VLANs do not make incompatible aggregation protocols interoperable. Inspect the configured channel-group modes and the EtherChannel protocol output before attempting to change system identifiers.
B:Two passive LACP peers do not initiate negotiation, but that is not the configuration described. The remote peer is active, and the Cisco interface is in PAgP desirable mode, so the mismatch is between negotiation protocols rather than two passive LACP participants. Changing the Cisco side to `channel-group 7 mode active` while configuring compatible settings on both ends is the relevant approach. Checking passive/passive compatibility would be appropriate for a different failure in an all-LACP environment.
C:A single conversation or flow can hash to one link in a correctly formed EtherChannel, which sometimes makes traffic distribution appear uneven. This issue is independent of whether the logical port-channel forms at all. Here the two physical links are up but are not bundled, and the configured negotiation technologies are incompatible. Link utilization or a load-distribution algorithm cannot explain a failure to exchange the expected LACP frames. First prove a valid logical bundle exists using EtherChannel and LACP status commands.
Question 206
A single large TCP connection saturates one physical member while others are nearly idle, with the port-channel and all member links healthy. The team should investigate which specific technical cause?
- LACP requires byte-by-byte equal use of every physical link by every individual TCP connection.
- EtherChannel load balancing hashes selected packet header fields per flow; one large flow may use a single member even when all links are healthy.
- A single TCP flow always uses more than one member because the Port-channel has multiple links.
- The member cables necessarily have different negotiated duplex even though all port metrics are healthy.
Explanation
Correct Answer
B:Bundles do not normally spray successive frames of one flow round-robin across all members. The selected source/destination MAC/IP or L4 fields determine the member, allowing many different flows to distribute.
Incorrect Answers
A:LACP negotiates link membership; load-balancing uses a hash that can pin one flow to one member.
C:A flow-hash aggregation design can keep all packets for a connection on one link to avoid reordering.
D:Observed hash imbalance does not prove PHY duplex incompatibility.
Question 207
A switching team must explain an outage. One member is removed, but the aggregate interface stays up and moves traffic over remaining active links with lower total capacity. Which diagnosis follows from these observations?
- All forwarding must stop until the removed member is restored, even with other active bundled members.
- Total bandwidth necessarily increases because fewer links reduce LACP overhead.
- The router should withdraw every VLAN route because a single physical member failed.
- The Port-channel remains operational because surviving bundled members forward; only available aggregate capacity decreases.
Explanation
Correct Answer
D:The bundle is a logical interface with member redundancy. Removing one eligible member does not necessarily drop the aggregate, provided enough links remain to meet any configured operational threshold.
Incorrect Answers
A:One-member loss is normally tolerated when remaining links satisfy configured bundle requirements.
B:LACP control overhead is not a substitute for lost physical link capacity.
C:A still-up Port-channel may continue carrying its VLANs; route withdrawal depends on actual L3 reachability and interface state.
Question 208
A switching team is validating a repair. Earlier, both members are configured mode passive at both ends; physical carrier exists but no ports become bundled because neither side initiates. Which postchange check most directly establishes the specific problem is resolved?
- Both ends still passive with no LACP neighbor while physical links are up/up.
- After changing at least one end to LACP active, `show lacp neighbor` identifies the partner system and ports, and `show etherchannel summary` reports bundled active members.
- A different access port has a CDP neighbor, but the intended channel members are still individual.
- A Port-channel interface name exists in the configuration but each member remains unbundled.
Explanation
Correct Answer
B:Passive/passive fails to initiate LACP. Partner adjacency and the bundle flags prove both protocol negotiation and member forwarding, not just electrical carrier.
Incorrect Answers
A:Carrier without exchanged LACPDUs does not establish the desired negotiated aggregate.
C:Discovery on another port does not validate LACP on the requested links.
D:Configuration existence does not prove successful LACP partner negotiation or member membership.
Question 209
The earlier fault was recorded as follows: One bundle member reports a different configured speed and shows suspended while the other members forward as a Port-channel. After corrective work, which observation provides direct evidence that the affected function now behaves correctly?
- The Port-channel itself is up but the corrected member still has a suspended flag.
- The member is administratively down, so it no longer reports a suspension warning.
- `show etherchannel summary` shows every intended member with a bundled `P` flag rather than `s`/suspended, and matched negotiated speeds.
- `show ip route` lists a default route while the Ethernet member is still suspended.
Explanation
Correct Answer
C:The prior defect was one suspended member caused by incompatible physical settings. A healthy Port-channel summary plus member attribute agreement confirms inclusion in the bundle.
Incorrect Answers
A:Another member may carry the aggregate; the specific suspended member defect remains unresolved.
B:A disabled member cannot prove the port has returned to the forwarding bundle.
D:Routing state alone cannot establish EtherChannel member eligibility.
Question 210
A switching team has repaired a network problem. The Port-channel trunk permits VLAN 20, but one member has incompatible access-port configuration and remains unbundled. Which device or protocol check is the strongest evidence that this particular failure is gone?
- The logical Port-channel permits VLAN 20 but the formerly faulty member is still unbundled.
- `show etherchannel summary` shows both intended physical links bundled, and `show interfaces trunk` shows the logical Port-channel forwarding VLAN 20.
- The physical links are up/up but `show interfaces trunk` lists neither the Port-channel nor VLAN 20.
- Only an unrelated VLAN 30 SVI is reachable.
Explanation
Correct Answer
B:The earlier issue was an access-mode member incompatible with a trunk Port-channel. Confirming both member inclusion and VLAN 20 transport demonstrates the corrected L2 aggregation.
Incorrect Answers
A:Trunk allowed list alone does not prove the member compatibility defect has been repaired.
C:Carrier does not prove tagged VLAN transport or successful bundle formation.
D:Reachability of a different VLAN does not test the failed VLAN 20 bundle membership.