CCNA Network Fundamentals: 339 practice questions

12 of the 339 Network Fundamentals questions in the Certsqill CCNA bank, shown in full below. Each one carries an explanation for every option, not just the correct one — the wrong answers are where the marks go.

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1. Workload B shares the host kernel: Which observation identifies the container-based workload?

1. Workload B requires a separate guest kernel.

   A separate guest kernel is characteristic of a virtual machine, not a conventional container.
2. Workload A uses a virtual network interface.

   Virtual machines commonly use virtual interfaces, but this does not identify their separate guest kernel.
3. Workload B shares the host kernel. ✓

   Containers normally share the host kernel while using isolation mechanisms for processes, filesystems, and networking.
4. Workload A shares the host kernel through process isolation.

   Workload A has virtual hardware and a guest kernel, indicating virtualization rather than containerization.

Containers share the host kernel; virtual machines normally provide separate guest kernels.

2. The /64 route: Which route does R1 use?

1. The /64 route, because it is the longest matching prefix. ✓

   The destination belongs to both prefixes, and the /64 provides the more specific installed route.
2. The /48 route, because it was learned through the WAN.

   The broader /48 matches, but IPv6 forwarding first prefers the most specific matching installed prefix.
3. Neither route, because IPv6 requires a /128 destination route.

   IPv6 routers routinely forward using summarized and subnet prefixes shorter than /128.
4. Both routes equally, because their prefixes begin identically.

   Routers select one best matching route rather than forwarding simultaneously across identical prefix beginnings.

Both prefixes match, but IPv6 forwarding selects the installed route with the longest prefix.

3. The endpoints have a duplex mismatch causing these: What is the most likely conclusion?

1. The switch port has negotiated an invalid Ethernet speed.

   Both endpoints report 100 Mb/s, so the observed fault concerns duplex rather than speed agreement.
2. The cable is limited to half-duplex operation.

   A passing cable and conflicting duplex settings point to configuration mismatch, not an inherent cable duplex limit.
3. The endpoints have a duplex mismatch causing these counters. ✓

   Full-duplex FCS errors and half-duplex late collisions strongly support mismatched duplex settings between peers.
4. The link is collision-free because Ethernet uses separate full-duplex paths.

   That statement applies only when both endpoints operate full duplex, which the peer evidence disproves.

Conflicting duplex states explain full-duplex errors at one endpoint and late collisions at the other.

4. 10.20.39.0: What is the network address?

1. 10.20.39.0 ✓

   Applying 255.255.255.0 clears the final octet's host bits, producing 10.20.39.0.
2. 10.20.39.22

   The supplied host address still contains host bits and therefore is not the subnet network address.
3. 10.20.39.255

   With a /24 mask, all host bits set to one identify the broadcast address, not the network address.
4. 10.20.0.0

   A /24 preserves the first three octets, so reducing the third octet incorrectly produces a larger network.

A /24 clears the final octet, so host 10.20.39.22 belongs to network 10.20.39.0.

5. The VLAN 20 gateway is down: Which dependency explains the VLAN 20 failure?

1. The VLAN 20 gateway is down. ✓

   The switch provides local Layer 2 connectivity, but the administratively down VLAN 20 gateway cannot route its traffic.
2. The access switch cannot learn MAC addresses.

   Successful communication between both VLAN 20 PCs demonstrates that local switching and MAC learning operate.
3. The PCs require a Layer 2 route between VLANs.

   Inter-VLAN communication requires Layer 3 routing, which depends on an operational VLAN 20 gateway.
4. The VLAN 30 router subinterface must be shut down.

   VLAN 30's up subinterface is unrelated to establishing the VLAN 20 gateway interface.

VLAN 20 switching works, but its router subinterface is administratively down and cannot provide a gateway.

6. The switch learns the source and forwards the frame: What happens immediately after ingress learning?

1. The switch learns the source and forwards the frame to Gi1/0/3. ✓

   The switch records the source on Gi1/0/7, then forwards the known destination unicast through Gi1/0/3.
2. The switch floods the frame because the source address is new.

   A new source address is learned, but the known destination still permits unicast forwarding directly to Gi1/0/3.
3. The switch learns the destination on Gi1/0/7 and filters the frame.

   Switches learn source MAC addresses, never the destination address from an arriving frame.
4. The switch rewrites both MAC addresses before forwarding within VLAN 30.

   Layer 2 switching preserves Ethernet addresses while forwarding a frame within the same VLAN.

The switch learns the ingress source MAC, then forwards the known destination unicast out Gi1/0/3.

7. The optics require compatibility verification before: Which conclusion is technically correct?

1. The link must work because both optics operate at 1 Gb/s.

   Matching nominal speed does not ensure compatible optical wavelength, fiber type, reach, or transceiver specifications.
2. The link must work because duplex LC connectors are interchangeable.

   Connector shape does not resolve differences between multimode SX and single-mode LX optical requirements.
3. The local optic automatically converts single-mode signals into multimode signals.

   Standard Ethernet optics do not automatically convert fiber modes merely because their connectors mate.
4. The optics require compatibility verification before the link is expected to operate. ✓

   SX multimode and LX single-mode specifications differ, so actual transceiver and fiber compatibility must be confirmed.

Equal speed and connectors do not prove compatibility between SX multimode and LX single-mode optics.

8. Access switches connect directly toward the combined core: Which TWO statements describe the collapsed-core ar

Select two. More than one option is correct — every correct one is ticked below.

1. A separate distribution layer remains between access and core.

   Keeping distinct distribution and core layers creates a three-tier hierarchy, contrary to the requirement.
2. Every leaf connects to every spine in a fabric.

   Leaf-to-every-spine connectivity describes a spine-leaf topology rather than a collapsed-core hierarchy.
3. Access switches connect directly toward the combined core. ✓

   The access layer uplinks toward the combined distribution-core function in a two-tier hierarchy.
4. All routing is removed from the campus design.

   Collapsed-core designs still provide central routing; they combine roles rather than eliminate Layer 3 functions.
5. Distribution and core functions are combined. ✓

   A collapsed-core design combines distribution and core roles into one layer or functional block.

Collapsed core combines distribution and core functions, with access switches connecting toward that combined layer.

9. 172.31.40.25: Which address is RFC1918 private?

1. 198.51.100.7

   198.51.100.0/24 is reserved documentation space, not an RFC1918 private address range.
2. 172.31.40.25 ✓

   172.31.40.25 falls within the RFC1918 172.16.0.0 through 172.31.255.255 private range.
3. 100.64.12.8

   100.64.0.0/10 is shared carrier space, specifically excluded from RFC1918 private addressing.
4. 169.254.18.9

   169.254.0.0/16 is IPv4 link-local addressing, not one of the RFC1918 private ranges.

172.31.40.25 is inside the RFC1918 172.16.0.0/12 private address block.

10. Reuse channel 1: Which conclusion is correct?

1. Use channel 14 because it is farthest from channel 11.

   Channel 14 is generally unavailable in the stated United States regulatory domain.
2. Reuse channel 1, 6, or 11 with adequate separation. ✓

   In the stated U.S. 20-MHz design, reuse of channels 1, 6, or 11 with sufficient spatial separation preserves the conventional nonoverlapping plan.
3. Use any permitted channel because 2.4-GHz channels do not overlap.

   Many 2.4-GHz channels overlap when 20-MHz channel widths are used.
4. Use channel 3.

   Channel 3 overlaps the 20-MHz channels already in use.

Reuse channels 1, 6, or 11 only with adequate separation.

11. TCP is working: Which conclusion best distinguishes transport reliability from application outcome?

1. TCP has failed because the application did not return usable data.

   TCP can reliably deliver bytes even when the application, database, or service dependency fails afterward.
2. The network must be dropping packets despite successful TCP acknowledgments.

   Acknowledgments and ordered delivery provide evidence that TCP is successfully handling the observed connection.
3. UDP should replace TCP because applications cannot depend on reliable transport alone.

   Changing transport protocols does not repair an unavailable application or its failed database dependency.
4. TCP is working, but the application or its database dependency may be failing. ✓

   Reliable transport confirms byte delivery, not that the server application successfully processes requests or reaches dependencies.

TCP can work correctly while an application or database dependency remains unavailable.

12. Global unicast addresses: Which address type should be assigned to the Internet-reachable workstation interfac

1. Global unicast addresses, because approved Internet services require routable IPv6 source and destination addresses. ✓

   Global unicast addressing provides the appropriate IPv6 scope for normal routed communication across the Internet.
2. Multicast addresses, because multiple research services can receive workstation traffic simultaneously.

   Multicast identifies receiver groups rather than providing ordinary globally reachable unicast workstation addressing.
3. Link-local addresses, because they support IPv6 communication without global routing.

   Link-local addresses remain limited to their local link and are not reachable across routed Internet paths.
4. Unique-local addresses, because they are designed for private internal IPv6 communication.

   Unique-local addresses support private routing domains but are not intended for global Internet reachability.

Global unicast addresses provide the required Internet-reachable IPv6 scope.

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