Cisco Certified Network Associate (CCNA) 200-301 Practice Test 20
Question 190
The interface remains physically up, but the peer disappears from the discovery table after the advertised holdtime passes. The team should investigate which specific technical cause?
- Carrier must have fallen because a CDP entry disappeared, although interface line protocol stayed up.
- The peer’s discovery advertisements stopped or were filtered, so its CDP/LLDP entry aged out even while the Ethernet link remained up.
- The interface learned no IPv4 default route, so its LLDP neighbor holdtime fell to zero.
- A tagged VLAN 20 frame exhausted the ARP cache and automatically erased all LLDP neighbors.
Explanation
Correct Answer
B:A link can continue carrying ordinary frames while discovery is administratively disabled or TLVs are filtered. Timer expiry with unchanged carrier favors a control-protocol receive problem over a physical interface flap.
Incorrect Answers
A:Discovery-table aging does not alone establish a PHY interruption.
C:LLDP aging is determined by local receipt and advertised TTL, not the IPv4 routing table.
D:ARP cache state is independent from discovery advertisement holdtime accounting.
Question 191
A switching team must explain an outage. A passive capture on the exterior switchport reveals the router's exact platform and software in CDP frames. Which diagnosis follows from these observations?
- The platform appears only in a TLS-encrypted SSH stream, not in CDP frames.
- CDP is enabled on the untrusted-facing port and is disclosing device platform and software information in plaintext link-local advertisements.
- The switch is leaking syslog messages to a remote NTP server, and CDP contains no device identifiers.
- A missing trunk native VLAN is the only way Cisco model information can be present in a CDP capture.
Explanation
Correct Answer
B:The capture itself confirms exposed CDP TLVs. The appropriate mitigation is to disable unneeded CDP on that interface; altering IP access lists may not block link-local discovery frames.
Incorrect Answers
A:The evidence explicitly identifies CDP advertisements; these are not SSH-encrypted sessions.
C:CDP can advertise platform/version TLVs. Syslog and NTP are separate IP services not established by this capture.
D:CDP visibility is controlled by discovery protocol operation, not uniquely by trunk native assignment.
Question 192
A switching team is validating a repair. Earlier, a cable swap changes the remote-device ID shown on Gi1/0/3 while the inventory still labels the original peer. Which postchange check most directly establishes the specific problem is resolved?
- The local port is up/up but `show cdp neighbors detail` still identifies the wrong remote device.
- An unrelated switch can ping a gateway while Gi1/0/3 remote port identity is unverified.
- The VLAN database contains the expected names but CDP still shows the former unexpected chassis.
- `show cdp neighbors detail` on Gi1/0/3 now reports the planned remote Device ID and Port ID, confirmed against physical cabling.
Explanation
Correct Answer
D:The defect was misidentified physical adjacency after a cable swap. Rechecking actual CDP remote identity and interface is a direct verification of corrected patching and inventory.
Incorrect Answers
A:Physical link success does not prove the correct adjacent peer and cable endpoint.
B:General IP reachability does not establish the intended directly connected neighbor/port mapping.
C:VLAN creation does not fix a mispatched physical cable.
Question 193
An engineer enables LLDP on a Cisco switch and its mixed-vendor uplink. Which observations best verify that LLDP actually exchanges neighbor information with the intended third-party switch?
- `show lldp` confirms global operation, `show lldp interface` confirms transmit/receive on the uplink, and `show lldp neighbors detail` identifies the remote chassis and port on that interface.
- `show cdp neighbors` lists a Cisco router on a different access port, without any LLDP output.
- `show spanning-tree root` confirms the root bridge priority for VLAN 10.
- `show errdisable recovery` lists BPDU Guard recovery timers but no neighbor details.
Explanation
Correct Answer
A:The test checks both prerequisites and observed protocol results. Global `show lldp` confirms the feature is active; interface status shows transmit and receive on the correct uplink; and neighbor detail supplies the advertised remote chassis identity and port ID. The combination avoids falsely passing a configuration that was saved but still does not exchange advertisements. LLDP detail is vendor neutral, so it is the right evidence for the third-party switch. This verification decision differs from identifying the earlier `no lldp run` root cause.
Incorrect Answers
B:CDP can discover compatible Cisco peers, but a CDP entry for a router on an unrelated port does not establish LLDP exchange with the intended third-party switch. LLDP and CDP are separate Layer 2 discovery protocols with different neighbor tables. Even correct CDP operation can coexist with globally disabled LLDP. The acceptance result must name the actual remote switch and its uplink port in LLDP neighbor detail, not rely on another device's CDP record.
C:Spanning-tree root information determines Layer 2 loop-prevention topology for a VLAN. It does not show whether LLDP is enabled, whether advertisements are transmitted on the uplink, or which third-party device is attached. A stable root bridge can exist while LLDP is completely disabled. Because the change was to the discovery protocol, inspect LLDP state and received neighbor TLVs directly instead of using STP status as a proxy.
D:BPDU Guard and errdisable recovery relate to protecting edge switchports and recovering from certain violation states. Those commands do not display received LLDP chassis or port identifiers, and the uplink in this scenario remains active. An errdisable timer does not prove a mixed-vendor LLDP neighbor was learned. Validate the LLDP global and interface modes, then read the neighbor detail output and compare it with the expected remote port on the diagram.
Question 194
A switching team is evaluating a deployment. Two Catalyst switches aggregate two physical links using IEEE 802.3ad LACP, with at least one peer actively sending LACPDUs. What approach correctly addresses the stated requirement?
- Configure passive on both peers and expect either side to send the first LACPDU to negotiate.
- Use Cisco PAgP `desirable` on one peer and LACP `passive` on the other.
- Configure matching `channel-group 1 mode active` on one peer and `mode passive` on the other, using consistent compatible member settings.
- Set channel-group mode `on` on one peer and rely on LACP negotiation with the other side.
Explanation
Correct Answer
C:LACP active sends negotiations; passive responds. Active/passive can form an IEEE LACP bundle, whereas passive/passive generally does not initiate negotiation. Confirm members show bundled in `show etherchannel summary`.
Incorrect Answers
A:Neither side initiates negotiation in passive/passive mode.
B:PAgP and LACP are different aggregation protocols and do not establish one common negotiated channel.
D:Static `on` does not exchange LACP control packets and is not a proper LACP pairing.
Question 195
A new Layer 2 EtherChannel has three candidate GigabitEthernet members. `show etherchannel summary` marks Gi1/0/3 suspended, while Gi1/0/1 and Gi1/0/2 bundle normally. Gi1/0/3 is configured as access VLAN 30; the other members are trunk ports carrying VLANs 30 and 40. Which fault should the engineer correct?
- LACP cannot bundle more than two active member links on any Cisco switch.
- A server's DNS TTL is longer than the port-channel's negotiation timer.
- The OSPF cost on a completely different routed link is lower than the EtherChannel cost.
- Member-interface Layer 2 settings are incompatible with the port-channel, so Gi1/0/3 cannot join until switchport mode and VLAN configuration match.
Explanation
Correct Answer
D:EtherChannel member ports must be compatible in relevant interface attributes, including switching mode and VLAN behavior. A port that is configured as an access interface cannot join a trunk port-channel whose other members use a consistent trunk configuration. Inspect `show etherchannel summary` and the member running configurations for mode, allowed VLANs, native VLAN and physical compatibility. Change Gi1/0/3 to the intended trunk settings using a coordinated configuration on the logical Port-channel and physical interfaces as supported by the platform. Then verify it changes from suspended to bundled and that traffic crosses all required VLANs.
Incorrect Answers
A:LACP can negotiate a multi-member link aggregate within platform and protocol limits; two links are not a universal hard maximum. The existing two bundled links show LACP is functioning. Gi1/0/3 is exceptional because of its incompatible Layer 2 switchport mode, not simply because it would become the third member.
B:DNS caching influences how long clients reuse a hostname's previously returned address. It does not determine whether an Ethernet interface can join an EtherChannel. The observed port suspension and differing access/trunk settings are local switch facts that can be checked without any DNS lookup.
C:OSPF path cost decides route preference among eligible Layer 3 paths; it does not control whether a specific physical switchport joins a Layer 2 EtherChannel. The failing interface is mismatched in switchport mode, a condition visible in the switch configuration and operational bundle flags.
Question 196
A switching team must implement a change. One logical Port-channel trunk carries VLANs 10 and 20 over multiple bundled physical links with consistent membership. Which technical decision most directly meets these requirements?
- Configure the logical `interface Port-channel1` as an 802.1Q trunk permitting VLANs 10 and 20 with the agreed native VLAN; keep every member compatible.
- Configure a trunk on only one member while leaving the other bundle member in access mode.
- Permit VLAN 20 on the switch physical access port but exclude it from the logical Port-channel trunk.
- Assign unrelated VLAN native IDs separately to bundled members and expect deterministic untagged mapping.
Explanation
Correct Answer
A:The Port-channel is the operational aggregate forwarding interface. Consistent access/trunk, allowed VLAN and native settings prevent member suspension and preserve one logical L2 path over multiple physical cables.
Incorrect Answers
B:Incompatible Layer 2 member attributes can keep the inconsistent port out of the bundle.
C:The logical Port-channel trunk VLAN membership controls usable VLAN transport for bundled links.
D:Members must present a consistent channel configuration; mismatched native VLAN semantics are unsafe.
Question 197
A routed aggregate link uses no switchport and an IP address on the logical Port-channel, not separate member IPs. The team needs a solution consistent with this requirement. Which option is the most appropriate design or configuration decision?
- Leave the Port-channel Layer 2-only and place a different IP address on each member.
- Create one VLAN SVI without configuring the routed Port-channel while expecting a direct L3 bundle interface.
- Set only `switchport mode trunk` on the logical Port-channel and assume it acquires an IP address automatically.
- Apply `no switchport` and the assigned routed IP address/mask to the logical `interface Port-channel10`; configure the physical members to join that routed channel.
Explanation
Correct Answer
D:For a Layer 3 EtherChannel, one logical routed Port-channel owns the subnet IP and participates in routing. Member links supply aggregate capacity and do not each act as separately numbered IP next hops.
Incorrect Answers
A:That is not the defined single logical routed aggregate; IP is assigned to the L3 Port-channel.
B:An SVI provides routing for a VLAN but does not itself convert an EtherChannel to a routed interface.
C:Trunking supplies multiple Layer 2 VLANs, not the required routed `no switchport` port-channel address.
Question 198
A switching team is evaluating a deployment. A Cisco switch connects to a non-Cisco device requiring standards-based LACP rather than Cisco-specific PAgP. What approach correctly addresses the stated requirement?
- Use Cisco PAgP `desirable` on one end and IEEE LACP active on the other.
- Configure both ends only as independent access links and trust STP to combine capacity into one aggregate.
- Configure static `mode on` on the Cisco and LACP passive on the peer.
- Use IEEE LACP (`channel-group ... mode active`/`passive`) on both vendors with compatible link and VLAN settings.
Explanation
Correct Answer
D:LACP is the standardized aggregation control protocol. Cisco PAgP uses different proprietary negotiation and should not be relied upon for interoperability with a non-Cisco device requiring LACP.
Incorrect Answers
A:PAgP and LACP cannot negotiate one standards-based bundle.
B:STP suppresses loops; it does not create an LACP Port-channel sharing active member links.
C:Static aggregation sends no LACP control messages to establish the required IEEE negotiation.
Question 199
Two 1-Gbps interfaces are bundled into a healthy LACP EtherChannel. A single TCP transfer consistently runs near 1 Gbps, while several independent transfers together approach 2 Gbps. What best explains this behavior?
- LACP allows traffic only on a single physical member until the other member fails.
- The switch hashes a flow to one member, so aggregate bandwidth can rise across multiple flows without splitting one flow per packet.
- The logical port-channel is operating in Layer 3 mode and therefore cannot forward a Layer 2 frame.
- The interface trunk native VLAN must be mismatched, so every second packet is silently discarded.
Explanation
Correct Answer
B:EtherChannel load balancing commonly chooses a member through a hash of fields such as source/destination MAC or IP and transport ports, with the supported hash inputs depending on hardware. Keeping packets of a given flow together avoids reordering. One elephant flow can therefore saturate one physical 1-Gbps port while other flows are placed on the second. A two-member bundle supplies approximately 2 Gbps of aggregate potential capacity across flows, not an automatic 2-Gbps rate for one TCP connection. Verify member flags and the configured load-balance method; use multiple source/destination flows to test aggregate distribution rather than relying on one throughput test.
Incorrect Answers
A:LACP negotiates compatible member ports and monitors partner state, but it does not deliberately hold all healthy member links idle until failure. A functioning bundle can forward simultaneous distinct conversations across separate members. If the other port were genuinely inactive, the EtherChannel summary would not show two bundled members. The described total throughput is evidence that both links can contribute capacity.
C:The evidence does not indicate the port-channel is routed or that Layer 2 forwarding is impossible. Whether the logical interface is Layer 2 or Layer 3 is configured independently of the fact that flows are hashed over physical members. A routed EtherChannel can still be subject to per-flow load distribution. The observed near-2-Gbps aggregate throughput supports a working bundle, not a forwarding-mode failure.
D:A native-VLAN mismatch concerns classification of untagged frames on 802.1Q trunks. It does not predict that one TCP flow tops out at one member's line rate while concurrent flows collectively use both links. An actual mismatch might create selected-VLAN connectivity errors and protocol warnings. Nothing in the given measurements demonstrates one, so changing VLAN settings would target the wrong failure layer.
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.