Cisco Certified Network Associate (CCNA) 200-301 Practice Test 3
Question 20
At a small collapsed-core campus, all access uplinks feed a distribution/core switch pair. Local LAN pings remain fast, no links are down, but latency rises sharply only during the daily simultaneous backup window. Uplink interfaces run near full utilization while core CPU remains low. What is the primary explanation?
- A core-tier hardware failure is proven because the network is a collapsed-core design.
- Oversubscribed access-to-distribution uplink capacity during the backup burst creates congestion and queueing despite healthy core forwarding.
- The destination routing table must be empty, although local and off-VLAN traffic completes outside the backup window.
- A native VLAN mismatch is proved by an otherwise healthy trunk reaching saturation only under backup load.
Explanation
Correct Answer
B:A physical port can remain up while carrying more offered load than its available bandwidth. Saturated uplink counters and timing tied to backups indicate oversubscription. Additional aggregate capacity, traffic scheduling or QoS may mitigate it; an invented core outage is not supported.
Incorrect Answers
A:The presented core pair has healthy hardware/CPU and the fault correlates with loaded uplinks.
C:A missing route would affect reachability persistently rather than only cause queueing at peak utilization.
D:A native VLAN mismatch can misclassify traffic, but no VLAN-specific symptom or warning appears in the evidence.
Question 21
A three-tier campus has working access switches and distribution uplinks. Multiple distribution blocks now lose throughput between buildings simultaneously, while their own local VLANs function normally. Core-facing interfaces report output drops and core throughput is pegged at capacity. Which component is the bottleneck?
- The dedicated campus core transit capacity is saturated; diagnose and expand or rebalance core throughput rather than replacing working access ports.
- A single workstation access port is administratively shut, so every building loses transit throughput.
- A failed DHCP address pool is proved by rising core interface output drops despite successful IP addressing.
- The distribution blocks have been removed because local VLAN communication remains healthy.
Explanation
Correct Answer
A:Inter-distribution traffic traverses the core, whereas local access forwarding need not. Simultaneous cross-building impact with drops on core interfaces points to transit congestion. Capacity planning should follow the measured bottleneck and high-availability design.
Incorrect Answers
B:One host-facing port cannot explain congestion observed on multiple core transit interfaces.
C:DHCP allocation failures do not directly produce the measured core transit saturation.
D:The remaining local operation contradicts a total distribution-tier failure.
Question 22
In a data-center design, leaf L1 serves servers in rack 1 and leaf L2 serves rack 2. Both normally have uplinks to spines S1/S2. A new topology diagram shows the only path from L1 to S2 is through L2, creating a dependency on the other rack. What architectural fault should be corrected?
- Remove both spine switches and make L1 the only routing hub for the entire fabric.
- Restore a direct L1-to-S2 spine uplink so each leaf attaches to the spine layer without depending on another leaf as transit.
- Convert the affected rack server links to a public WAN service rather than fix the missing internal uplink.
- Enable PortFast on every spine transit interface because it creates physical L1-to-S2 connections.
Explanation
Correct Answer
B:The characteristic leaf-spine fabric has every leaf independently connect to each spine. Inter-leaf traffic may traverse a spine, but chaining one leaf through another creates an avoidable intermediate failure dependency and nonuniform paths.
Incorrect Answers
A:This further centralizes the fabric and removes required spine-level redundancy.
C:An external provider circuit is not a substitute for internal fabric adjacency.
D:STP PortFast cannot create a missing physical topology connection or routing adjacency.
Question 23
A SOHO router has a working public WAN IP and can ping the ISP next hop. A private-address workstation reaches the router but cannot reach Internet destinations. The NAT rule for inside 192.168.50.0/24 sources was accidentally removed; other public WAN tests succeed. Which failure is most consistent?
- The ISP access circuit is down even though the router can ping the carrier next hop and its public WAN tests succeed.
- The local SOHO router is not translating RFC1918 source addresses at its Internet edge, rather than suffering an ISP access-link outage.
- The workstation must switch to IPv6 multicast to reach an IPv4 Internet server.
- The router must replace its Ethernet physical cable because only the private LAN host fails while public WAN tests pass.
Explanation
Correct Answer
B:The provider path remains up and externally sourced router traffic succeeds. A private LAN host normally needs inside source NAT/PAT to communicate across a public Internet boundary; the missing translation policy specifically affects those inside sources.
Incorrect Answers
A:Successful provider reachability contradicts a complete carrier link outage.
C:Multicast cannot substitute for IPv4 private-source translation.
D:A complete cable failure would not selectively remove only inside-NAT translations.
Question 24
An access switch has two uplinks to the collapsed distribution/core pair. Before signing off a topology change, an engineer needs to prove that loss of either one uplink still leaves a routed path to the server VLAN. Which test is most decisive?
- Check that two Ethernet cables are physically plugged in without inspecting VLAN, routing or failover state.
- Only check the Internet public DNS A record because that proves each campus uplink remains reachable.
- Inspect neighbor and active forwarding paths, fail one uplink under controlled conditions, and confirm the alternate uplink carries the server-VLAN traffic.
- Disable both uplinks simultaneously and interpret total isolation as a successful single-link failover.
Explanation
Correct Answer
C:The acceptance criterion is path resilience through the aggregation boundary. Topology evidence plus an actual controlled failure test demonstrates which failure domain is protected. Simply seeing two installed cables does not prove forwarding will switch correctly.
Incorrect Answers
A:Physical cabling alone does not prove the alternate uplink is allowed to forward or supplies a valid next hop.
B:Name resolution cannot establish the internal redundant aggregation path.
D:Testing double failure violates the one-uplink resilience requirement and prevents observing the intended alternate path.
Question 25
A campus has separate access, distribution and core tiers. A workstation can reach its distribution SVI but cannot reach a remote building subnet. Which evidence sequence best identifies the actual failing tier?
- Trace the client access VLAN and gateway first, then the distribution route, then the core-to-remote-distribution transit and return path.
- Inspect only the client NIC speed and declare the core healthy without checking any routed hops.
- Look only at the provider Internet firewall NAT counters despite the destination being inside another campus building.
- Check only a remote DNS server without verifying any gateway or route, because an IP destination always requires DNS.
Explanation
Correct Answer
A:A tiered troubleshooting path isolates access membership, routed distribution boundary and core transit in order. Reaching the local SVI already supports local access and gateway; routing and transit evidence must show where a remote path is lost.
Incorrect Answers
B:Physical client connectivity does not validate distribution or core forwarding.
C:The problem is an internal campus path, not necessarily an Internet translation boundary.
D:Direct IPv4 routing and traceroute are possible without resolving a hostname.
Question 26
Leaf switches L1 and L2 connect to spines S1 and S2 via equal-speed routed links. After enabling ECMP in the underlay, what observed forwarding result best confirms the expected topology for traffic between racks?
- Every inter-rack packet must traverse both spines serially before reaching L2.
- The only route from L1 to L2 must traverse a third server-facing leaf as a transit router.
- A single leaf-to-leaf copper wire replaces all spine uplinks and still proves redundant equal-cost routing.
- Routes from L1 toward L2 show equal-cost next hops via S1 and S2; each inter-rack path crosses a spine and has the same leaf-spine-leaf hop count.
Explanation
Correct Answer
D:The fabric offers two equivalent paths between leaves through either spine. With suitable routing and equal metrics, the FIB can install ECMP next hops while each specific flow may hash to one path. Consistent two-link paths are characteristic of the design.
Incorrect Answers
A:The alternatives are parallel forwarding paths, not two consecutive spine hops for each packet.
B:Standard spine-leaf fabric transit is through spines rather than other leaves.
C:An isolated direct leaf cable is not proof of parallel spine routes or multipath resilience.
Question 27
A branch uses an MPLS WAN to a headquarters router and a separate private cloud virtual network tunnel. It must confirm which edge actually carries 10.30.0.0/16 and that traffic follows the intended branch-to-cloud path. Which method best validates the demarcations?
- Verify only that branch access switch ports are green while ignoring next hops and cloud route tables.
- Inspect branch route and next-hop decisions, trace across the provider and cloud gateway boundaries, and verify return routing for 10.30.0.0/16.
- Read only the cloud application certificate expiration date and assume this shows all WAN transit hops.
- Change all branch endpoints to the cloud gateway IP without verifying that gateway or provider routes exist.
Explanation
Correct Answer
B:WAN and cloud boundaries are distinct handoff points. Route selection and a controlled destination trace reveal whether traffic uses provider transit, tunnel termination and cloud routing as intended. A one-way trace alone cannot prove bidirectional service.
Incorrect Answers
A:Local switch links do not establish the remote cloud forwarding path.
C:A TLS certificate does not disclose Layer 3 provider and cloud demarcation paths.
D:Readdressing clients is not a substitute for tracing the actual Layer 3 handoffs.
Question 28
A new office requires a 60-meter 1-Gb/s desk-to-access-switch connection over standard structured cabling. The same rack has conventional RJ-45 Ethernet access ports and no need for optical distance or electrical isolation. Which medium is appropriate?
- Install a standards-compliant Cat5e-or-better twisted-pair copper Ethernet link with tested RJ-45 terminations.
- Use a 130-meter Cat5 cable channel without testing, since 1000BASE-T supports unlimited copper length.
- Use a single-mode transceiver without optical-capable ports because an SFP fiber module plugs directly into any RJ-45-only NIC.
- Replace the Layer 1 desk cable with a default IPv4 static route to extend physical reach.
Explanation
Correct Answer
A:A 60-meter copper permanent/channel run is within the ordinary 100-meter Ethernet channel distance for supported 1000BASE-T structured cabling. Correct category and termination are important; fiber optics would not be required solely for this short copper-access use.
Incorrect Answers
B:The proposed copper channel exceeds the conventional 100-meter limit and is not the stated reliable design.
C:RJ-45 copper access interfaces cannot terminate an unsupported optical transceiver.
D:Routing changes do not provide the required physical connection.
Question 29
A company needs a 4-kilometer high-bandwidth link between buildings across a campus. It can install appropriate single-mode optics at both ends and wants optical reach beyond ordinary multimode campus transceiver budgets. Which cable type should the designer select?
- Run a 4-kilometer twisted-pair Ethernet channel because 1000BASE-T copper supports kilometer distances.
- Select single-mode fiber with transceivers rated for the required reach, wavelength, connector and optical budget.
- Choose an ordinary short-reach multimode optic merely because its connector fits the single-mode port.
- Use a single coaxial drop and a 100BASE-TX copper-only transceiver as the optical path.
Explanation
Correct Answer
B:Single-mode fiber supports long optical spans when paired with compatible optics and optical loss budgeting. It has a smaller core and is commonly used for kilometer-scale building or metro links; reach is defined by the matched optic and fiber plant, not the term fiber alone.
Incorrect Answers
A:The proposed length exceeds ordinary twisted-pair Ethernet channel limits.
C:Connector appearance cannot compensate for the wrong fiber type/reach budget.
D:Coaxial/copper PHY is not the specified kilometer-scale optical transceiver solution.
Question 30
Two data-center rooms are 75 meters apart. Both switches have 10GBASE-SR multimode transceivers, and the installed OM4 fiber passes optical power testing. Which medium fits these installed optics?
- Substitute single-mode fiber on one side while leaving both 10GBASE-SR multimode optics unchanged.
- Use the OM4 multimode fiber plant with compatible 10GBASE-SR optics at both ends.
- Run a 75-meter analog telephone pair without Ethernet cable qualification because all twisted pairs carry 10 Gb/s.
- Use 1000BASE-LX optics at one end and 10GBASE-SR at the other because the wavelength difference is harmless.
Explanation
Correct Answer
B:Short-reach 10GBASE-SR optics are specified for multimode fiber with a defined optical link budget. A 75-meter OM4 span is normally within supported reach; installed optics and supported media must be matched instead of selecting fiber based only on distance.
Incorrect Answers
A:Changing media without matching the optical transceiver specification is not a valid interoperable design.
C:A telephone pair without the required Ethernet PHY/cable category is not the specified 10GBASE-SR fiber plant.
D:Different speeds and transceiver modes cannot establish the intended compatible 10-Gb/s link.
