Network+ Network Implementation: 420 practice questions

12 of the 420 Network Implementation questions in the Certsqill Network+ 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. Longest matching prefix: Which route-selection principle determines the chosen entry?

1. Protocol metric

   Metrics select among routes within a protocol, not between different destination prefix lengths in forwarding.
2. Longest matching prefix ✓

   10.20.30.44 matches both /16 and /24, but /24 is more specific, so longest-prefix forwarding selects it first.
3. Administrative distance

   Administrative distance compares route sources for the same prefix; it does not override a more specific installed prefix.
4. Default-route preference

   The default route matches broadly but is used only when no more specific installed route matches the destination.

The destination matches /16 and /24, so the /24 route wins because forwarding uses the longest matching prefix.

2. A default route with a zero-length network prefix: Which route feature directly satisfies this requirement?

1. A default route with a zero-length network prefix ✓

   A 0.0.0.0/0 route matches any IPv4 destination not covered by a more specific installed route.
2. A floating static route with a higher preference value

   A floating static route provides backup selection, but its prefix still determines which destinations it can match.
3. A virtual gateway address shared by redundant routers

   A virtual gateway improves first-hop availability but does not itself define routes for otherwise unknown destinations.
4. A host route with a thirty-two-bit prefix

   A /32 route matches only one IPv4 destination and cannot provide catch-all forwarding for unknown networks.

A default route, 0.0.0.0/0, provides catch-all forwarding only when no more specific route matches.

3. Configure a static route: Which approach best fits?

1. Advertise the network through an external routing policy

   External policy mechanisms are designed for interdomain control and exceed the needs of a small fixed network.
2. Configure a static route ✓

   A static route supplies explicit reachability with little protocol overhead when topology and next-hop information remain stable.
3. Install a first-hop redundancy virtual address

   First-hop redundancy protects gateway availability but does not create the required route toward the remote network.
4. Enable an interior dynamic routing protocol

   Dynamic routing can work, but it adds exchanges and operational complexity unnecessary for a stable, small topology.

A static route directly supplies stable reachability without the overhead of a dynamic routing protocol.

4. Dynamic routing with automatic convergence: Which capability directly meets the requirement?

1. A default route pointing toward one WAN

   A single default route provides fallback forwarding but does not automatically learn or select alternate paths after failure.
2. Static routes with manually scheduled replacement

   Scheduled replacement still requires administrative intervention and cannot reliably react to unpredictable link failures.
3. Dynamic routing with automatic convergence ✓

   Dynamic routing exchanges topology information and recalculates reachable paths after failures, reducing manual recovery across routers.
4. PAT with multiple translated source ports

   PAT multiplexes flows through translated ports but does not discover paths or recalculate routes after link failure.

Dynamic routing protocols exchange reachability and converge on alternate paths after failures without per-device manual edits.

5. Link-state advertisements and a topology database: Which protocol characteristic directly supports this requir

1. Translated address mappings and port multiplexing

   NAT and PAT alter addressing and ports, but they do not distribute topology or calculate routing paths.
2. Interdomain policy announcements between autonomous systems

   Interdomain policy announcements support BGP-style control between autonomous systems, not the stated internal topology model.
3. Link-state advertisements and a topology database ✓

   Link-state protocols distribute topology information, allowing routers to construct a shared database and calculate shortest paths.
4. Neighbor distance vectors and periodic route advertisements

   Distance-vector operation shares reachable distances rather than building the complete link-state topology database described.

Link-state advertisements create a shared topology database from which routers calculate internal paths.

6. BGP: Which protocol is the direct fit?

1. OSPF

   OSPF is an interior link-state protocol intended for routing within an administrative domain rather than provider policy exchange.
2. PAT

   PAT multiplexes private flows through translated ports but does not exchange routing prefixes between autonomous systems.
3. EIGRP

   EIGRP is an advanced distance-vector interior protocol and is not the standard interdomain policy protocol.
4. BGP ✓

   BGP is designed for interdomain route exchange and supports policy decisions between autonomous systems.

BGP provides policy-controlled route exchange between autonomous systems, matching the provider connection requirement.

7. EIGRP, an advanced distance-vector interior protocol using: Which protocol best fits?

1. EIGRP, an advanced distance-vector interior protocol using a composite metric ✓

   EIGRP matches the explicitly required protocol family, interior scope, and composite-metric behavior.
2. FHRP

   FHRP provides first-hop gateway redundancy rather than end-to-end route calculation.
3. OSPF

   OSPF is a link-state interior protocol, not the specified advanced distance-vector protocol with a composite metric.
4. BGP

   BGP is an interdomain policy-routing protocol, contrary to the stated interior requirement.

EIGRP directly matches the stated advanced distance-vector and composite-metric requirements.

8. Administrative distance: Which feature directly satisfies the requirement?

1. Equal-cost load balancing

   Equal-cost load balancing distributes traffic among equivalent routes but does not establish trust between competing route sources.
2. Administrative distance ✓

   Administrative distance ranks candidate route sources for the same prefix, allowing configured trust preference to select one source.
3. Protocol metric

   A metric selects among routes within a routing protocol; raw metrics should not directly compare OSPF and static routes.
4. Longest-prefix matching

   Longest-prefix matching selects the most specific destination prefix, not the preferred source when prefixes are identical.

Administrative distance selects between route sources advertising the same prefix; metrics operate within a protocol instead.

9. Compare EIGRP composite metrics among EIGRP paths: Select TWO valid comparisons.

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

1. Compare EIGRP composite metrics among EIGRP paths ✓

   EIGRP compares its composite metric among EIGRP paths, subject to protocol-specific feasibility and selection rules.
2. Compare OSPF costs among OSPF paths ✓

   OSPF uses its cost metric to compare eligible OSPF paths toward the same destination.
3. Compare OSPF cost directly with BGP local preference

   OSPF cost and BGP local preference belong to different protocols and are not directly comparable numeric metrics.
4. Compare static-route distance with OSPF cost

   Static-route administrative distance and OSPF cost answer different selection questions and should not be compared directly.
5. Compare administrative distance with EIGRP metric

   Administrative distance compares route sources, whereas EIGRP metric compares paths within EIGRP.

Compare metrics only within their respective protocols; OSPF cost and EIGRP composite metric are valid examples.

10. Static one-to-one NAT: Which feature is appropriate?

1. Static one-to-one NAT ✓

   Static one-to-one NAT permanently maps one public address to one private address for predictable bidirectional translation.
2. First-hop redundancy protocol

   FHRP provides a resilient default gateway address and does not translate private server addresses.
3. Dynamic NAT pool

   Dynamic NAT assigns addresses from a pool temporarily, so it does not guarantee one permanent public mapping.
4. Port address translation

   PAT multiplexes multiple private hosts through shared public addressing by distinguishing sessions with transport ports.

Static one-to-one NAT provides a stable public-to-private address mapping without multiplexing multiple hosts through ports.

11. Port address translation: Which feature best explains the design?

1. Static one-to-one NAT

   One-to-one NAT dedicates a public address to each private host rather than multiplexing sessions through one address.
2. Dynamic NAT using a public address pool

   A pool-based design allocates public addresses; the capture shows one shared address with differing ports.
3. Port address translation ✓

   PAT lets multiple private hosts share one public address by distinguishing simultaneous sessions with translated transport ports.
4. Virtual gateway redundancy for the shared public address

   Gateway redundancy preserves first-hop availability but does not create session-specific translations.

PAT multiplexes multiple private sessions through one public address using distinct translated ports.

12. Port forwarding: Select TWO appropriate inbound translation features.

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

1. First-hop redundancy protocol

   FHRP supplies a resilient gateway address for hosts but does not translate public traffic to an internal server.
2. Dynamic NAT pool

   Dynamic NAT assigns temporary addresses to hosts and does not provide a predictable inbound service destination.
3. Port forwarding ✓

   Port forwarding maps a selected public destination port to a specific internal server and service port.
4. Static one-to-one NAT ✓

   Static one-to-one NAT maps a public address directly to the internal server, supporting inbound access to its services.
5. Outbound PAT

   Outbound PAT primarily represents internal clients externally and does not inherently publish an unsolicited inbound service.

Static NAT publishes a host address, while port forwarding publishes a selected service; both support inbound translation designs.

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