Cisco Certified Network Associate (CCNA) 200-301 Practice Test 19
Question 180
A switching team is validating a repair. Earlier, the switches report different native VLAN IDs, and untagged control frames are assigned to different VLANs at the two ends. Which postchange check most directly establishes the specific problem is resolved?
- Both peers list VLAN 20 in the VLAN database while continuing to use different native IDs.
- Only a different switch user-access VLAN is checked; trunk native settings are not inspected.
- All physical interface counters are zero after shutting down the link for the test.
- Both interfaces report the same trunk native VLAN ID, and controlled untagged test frames are learned in that intended VLAN on the receiving side.
Explanation
Correct Answer
D:The earlier fault classified untagged control and data frames inconsistently. Aligning `show interfaces ... switchport` native IDs plus verifying receive-side VLAN mapping directly tests that behavior.
Incorrect Answers
A:VLAN existence does not correct where untagged trunk frames are classified.
B:Unrelated endpoint VLAN memberships cannot validate the trunk’s native untagged mapping.
C:A disabled trunk cannot demonstrate correct forwarding of untagged frames.
Question 181
The earlier fault was recorded as follows: An interface with working physical carrier remains operationally access mode and cannot convey tagged frames for the second VLAN. After corrective work, which observation provides direct evidence that the affected function now behaves correctly?
- The port is physically up but still says `Operational Mode: static access`.
- `show vlan brief` lists VLAN 20 while the uplink is untagged access-only.
- `show interfaces <uplink> switchport` reports operational mode trunk and `show interfaces trunk` lists VLAN 20 as carrying/forwarding.
- The host’s IP address is in VLAN 20’s subnet but no tagged frames arrive on the uplink.
Explanation
Correct Answer
C:The failed link previously operated as access despite working carrier. Operational trunk mode and actual second-VLAN forwarding establish that 802.1Q transport is restored.
Incorrect Answers
A:Carrier alone does not permit multiple VLAN tags over an access-mode link.
B:Local VLAN existence cannot prove the necessary interswitch trunk exists.
D:A valid host address is insufficient if the trunk still filters the VLAN.
Question 182
A switching team has repaired a network problem. Both interfaces are configured dynamic auto, so neither initiates desirable trunk negotiation and show interfaces trunk is empty. Which device or protocol check is the strongest evidence that this particular failure is gone?
- Keep dynamic auto on both ends and check only that the physical link LEDs are lit.
- At least one DTP peer is changed to `dynamic desirable` or both to explicit trunk; the link appears operationally trunk in `show interfaces trunk`.
- Set both ports to `switchport mode access` and assume this initiates DTP trunking.
- Apply `switchport nonegotiate` to both dynamic-auto ports without selecting trunk mode.
Explanation
Correct Answer
B:Two `dynamic auto` Cisco ports may remain access because neither initiates trunking. The requested evidence is negotiation/configuration yielding the operational trunk state.
Incorrect Answers
A:Two passive DTP peers can have carrier without forming a trunk.
C:Explicit access mode is incompatible with the desired trunk forwarding.
D:Suppressing DTP cannot turn a passive/passive pairing into a working negotiated trunk.
Question 183
A network acceptance test follows this reported failure: The switch allows VLAN 40, but router Gi0/0.40 is configured encapsulation dot1q 50 and VLAN 40 cannot reach its gateway. Which verification most specifically demonstrates the repaired function rather than checking an unrelated feature?
- `show interfaces trunk` lists VLAN 40 on the switch while the router subinterface is still dot1q 50.
- The router interface name ends in `.40` although its encapsulation command continues to specify VLAN 50.
- VLAN 50 hosts can reach another gateway while VLAN 40 still cannot reach its configured gateway.
- `show run interface Gi0/0.40` displays `encapsulation dot1Q 40` and the correct VLAN 40 gateway IP; clients on VLAN 40 can ping that gateway.
Explanation
Correct Answer
D:The original subinterface accepted VLAN 50 instead of 40. Matching VLAN 40 encapsulation and successful VLAN 40 L3 reachability are directly relevant acceptance evidence.
Incorrect Answers
A:The switch side alone does not fix the router tag mismatch.
B:The dotted subinterface suffix does not determine actual 802.1Q tag matching.
C:Success on the different tagged VLAN does not verify the affected VLAN40 path.
Question 184
A switching team must implement a change. Cisco switchports identify directly connected Cisco peers and remote interface IDs with CDP advertisements and neighbor output. Which technical decision most directly meets these requirements?
- Run `show cdp neighbors detail` on the local Cisco device and correlate neighbor Device ID, local interface and neighbor Port ID.
- Use `show ip route` to identify the physical neighbor port and platform for every switch uplink.
- Use only `show mac address-table` to obtain the remote Cisco device hostname and exact remote interface.
- Run CDP on an arbitrary remote router several hops away and treat the entry as directly connected.
Explanation
Correct Answer
A:CDP advertisements describe directly connected Cisco neighbors, including identity and interface/platform details. The detail output verifies the actual physical peer; it does not infer connectivity across routed hops.
Incorrect Answers
B:Routing table entries reveal next-hop prefixes or gateways, not CDP remote Port IDs or Cisco chassis model.
C:A MAC table resolves learned source MACs to local ports; it does not inherently reveal remote port names/platform metadata.
D:CDP advertisements are link-local; they are not forwarded across routed networks.
Question 185
A mixed-vendor access switch needs LLDP transmit and receive enabled to discover the directly attached non-Cisco peer. The team needs a solution consistent with this requirement. Which option is the most appropriate design or configuration decision?
- Enable LLDP globally with `lldp run` and ensure LLDP transmit/receive is permitted on the relevant interface; inspect `show lldp neighbors detail`.
- Use Cisco-only CDP as the sole discovery method and assume every third-party device advertises CDP.
- Enable only `ip routing` and expect LLDP neighbor entries to cross routed hops.
- Disable LLDP receive on the interface while expecting to learn the neighbor through LLDP.
Explanation
Correct Answer
A:IEEE LLDP is interoperable across different vendors and exchanges link-local identity, port and capabilities TLVs. Both devices must send and receive as required and not filter LLDP on the physical link.
Incorrect Answers
B:CDP is Cisco-proprietary; LLDP is the appropriate standards-based choice for mixed-vendor discovery.
C:L3 forwarding does not originate or propagate LLDP data-link advertisements.
D:A port prevented from receiving LLDP advertisements cannot learn that peer through the protocol.
Question 186
A switching team is evaluating a deployment. CDP/LLDP neighbor entries expire when periodic control advertisements stop and their hold timer reaches zero. What approach correctly addresses the stated requirement?
- The neighbor advertisement aged out when new CDP/LLDP TLVs stopped arriving before the holdtime expired.
- The neighbor entry is permanent until the local switch reloads, regardless of control advertisements.
- The remote neighbor must have sent an IP routing withdrawal because LLDP depends on OSPF reachability.
- Any expired CDP holdtime proves the copper cable has physically lost carrier.
Explanation
Correct Answer
A:Discovery entries are maintained by periodic link-local advertisements. If these stop, the hold timer can expire and remove a neighbor entry even when a physical interface remains up; inspect timers and receive counters.
Incorrect Answers
B:CDP and LLDP neighbor entries normally expire after their advertised TTL/holdtime.
C:LLDP is link-local Layer 2 discovery, not an OSPF route announcement.
D:A discovery protocol can stop transmitting or receiving while carrier remains up.
Question 187
A proposed network design has this requirement: An untrusted public-facing interface should not broadcast internal device model and platform details through CDP. Which choice is technically appropriate for that deployment?
- Enable `cdp run` globally and assume encryption protects CDP advertisements.
- Change the switchport native VLAN and leave CDP enabled toward the untrusted network.
- Disable CDP advertisement on the untrusted interface with interface-level `no cdp enable` (or disable CDP globally if policy requires).
- Change the router default route but leave the discovery daemon transmitting on the exterior port.
Explanation
Correct Answer
C:CDP can reveal device model, software and connectivity information to anyone observing the local segment. Disabling it on untrusted external edges reduces unnecessary exposure without affecting IP forwarding.
Incorrect Answers
A:CDP is not an encrypted confidentiality service; enabling it can expose neighbor identity and platform details.
B:Native VLAN classification does not prevent link-local discovery information from being advertised.
D:IP routing changes do not stop CDP frames being emitted on that interface.
Question 188
A switching team collects this evidence: A cable swap changes the remote-device ID shown on Gi1/0/3 while the inventory still labels the original peer. Which root-cause interpretation best fits the observations?
- The actual cable terminates on a different directly attached device or port than the inventory describes; update physical mapping after confirming CDP identity.
- The original inventory label conclusively identifies the current remote peer despite contradictory CDP detail output.
- A missing OSPF default route changes the neighbor hostname advertised in CDP without changing the cable.
- The client DNS search suffix rewrites CDP Port IDs on local Ethernet links.
Explanation
Correct Answer
A:CDP Device ID and remote Port ID learned on local Gi1/0/3 reflect directly connected physical adjacency. A changed identity after a cable swap is evidence of different wiring or an altered neighbor.
Incorrect Answers
B:A static document can be stale after recabling; compare the observed live neighbor IDs with patch panel evidence.
C:Routing state does not rename the directly connected CDP speaker as a side effect.
D:CDP advertises device and interface identifiers independently of endpoint DNS suffixes.
Question 189
A Cisco Catalyst switch is cabled to a third-party switch. The Ethernet link and VLAN traffic work, but `show lldp neighbors` is empty. The Cisco configuration contains `no lldp run`, so no global LLDP transmissions or receptions occur. Which configuration issue specifically explains the missing multivendor discovery?
- A CDP neighbor message reports an unexpected remote device ID on a different interface.
- LLDP is disabled globally and cannot advertise or learn neighbors until enabled on the device and relevant interfaces.
- The LLDP holdtime was reduced, but the device continues sending normal advertisements.
- The physical interface is disabled and no Ethernet frames can cross the interswitch link.
Explanation
Correct Answer
B:The `no lldp run` configuration disables global LLDP operation on the Cisco device. A physically healthy link and correct VLAN traffic do not cause LLDP neighbors to appear when the local protocol is turned off. Enable LLDP globally where policy permits, ensure transmit and receive settings on the relevant interface, and allow advertisements to populate the neighbor table. Confirm operation using `show lldp`, `show lldp interface`, and neighbor detail. This is the root-cause diagnosis; the related verification card tests the resulting topology information after the correction.
Incorrect Answers
A:CDP is a Cisco discovery protocol, and its neighbor output can help identify Cisco devices and cabling mismatches. A CDP device ID from a different interface does not explain why LLDP is globally disabled on the current Catalyst switch. The scenario specifically tests discovery of a non-Cisco neighbor on a working Ethernet link. Use LLDP global and interface status first; CDP is not a substitute for the vendor-neutral protocol in this mixed-vendor environment.
C:A short LLDP holdtime can cause entries to age out rapidly when periodic advertisements are interrupted, but the scenario does not describe intermittent entries or incoming LLDP traffic. It explicitly shows a global `no lldp run` state, which prevents normal protocol operation. Adjusting timers would not turn LLDP back on. First restore the global feature and interface transmit/receive behavior, then investigate advertisement intervals only if neighbors continue to appear and disappear unexpectedly.
D:An administratively shut or physically failed port can prevent neighbor discovery, but the question states that the Ethernet link and VLAN traffic operate normally. That evidence rules out a complete physical link outage as the primary cause. LLDP uses Layer 2 frames and can be disabled independently of data-plane forwarding. Inspect the global protocol configuration and interface LLDP status instead of assuming that a missing discovery entry always means a cable or interface failure.
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.