Question 1

Route selection by administrative distance: If a routing table contains a static route, a RIP route, and an IGRP route to the same destination network, which route will the router prefer by default?

Accepted Answer

Introduction / Context: Routers often learn multiple routes to the same destination from different sources. The tie-breaker among protocols is administrative distance (AD), a trust metric where lower values are preferred. Understanding AD is critical to predicting which path will be installed in the routing table and used for forwarding. Given Data / Assumptions: Three candidates exist: static, RIP, and IGRP. All routes point to the same prefix with viable next hops. No policy overrides (e.g., floating static with higher AD) are in play. Concept / Approach: Default administrative distance values (classic IOS) are: connected 0, static 1, EIGRP summary 5, eBGP 20, IGRP 100, OSPF 110, IS-IS 115, RIP 120. The route with the lowest AD wins and is installed in the routing table. Static routes use AD 1 unless configured otherwise. Step-by-Step Solution: Compare ADs: static (1) vs IGRP (100) vs RIP (120).Identify the lowest → static (1).Conclude the router will choose the static route by default. Verification / Alternative check: Run show ip route and observe the installed entry’s code and administrative distance/metric in brackets. Removing the static route should reveal the next-best protocol path (IGRP, then RIP). Why Other Options Are Wrong: RIP and IGRP have higher ADs, so they lose to the static route. Load-balancing occurs only among equal-AD, equal-metric routes; differing AD prevents that. “Any available route” ignores the deterministic AD selection rule. Common Pitfalls: Forgetting that you can raise a static route’s AD (floating static) to act as a backup; confusing protocol metrics with administrative distance—they solve different problems. Final Answer: Static route

Question 2

Controlling RIP advertisements: Which command suppresses RIP updates from being sent out a specific interface while still allowing that interface to receive RIP updates (i.e., passive on that interface)?

Accepted Answer

Introduction / Context: On edge or user-facing interfaces, you generally do not want a routing protocol to form neighbor relationships or spew periodic updates, yet you may still want to learn routes or at least advertise the connected network via other active interfaces. The passive-interface feature provides exactly this control. Given Data / Assumptions: The routing protocol is RIP (distance-vector, periodic updates). We want to stop outbound RIP updates on a chosen interface. We still allow reception of updates (where applicable) and keep the network in the process. Concept / Approach: The correct context is the routing process configuration mode. From router rip, issue passive-interface (e.g., s0). This prevents outbound updates on that interface while maintaining the interface in the RIP process. On broadcast-based RIP, the router will not send updates out but can still process received ones. Step-by-Step Solution: Enter: router ripType: passive-interface s0Verify with: show ip protocols (lists passive interfaces) Verification / Alternative check: Packet captures on interface s0 should show no outbound RIP updates while other RIP neighbors remain unaffected. show ip rip database confirms learned routes still exist via other interfaces. Why Other Options Are Wrong: Option A is not a valid method to control RIP; it disables routing on an interface broadly (and is not standard syntax). Option B uses interface configuration mode; passive needs to be under the protocol process, not per-interface config mode. Option D is not valid IOS syntax. Common Pitfalls: Confusing passive-interface behavior across protocols (e.g., OSPF passive prevents forming adjacencies entirely); forgetting to verify passive settings after template deployments. Final Answer: Router(config-router)# passive-interface s0

Question 3

Concept of route poisoning: In distance-vector routing, what does the term “route poisoning” specifically describe when a link or network goes down?

Accepted Answer

Introduction / Context: Distance-vector protocols such as RIP exchange periodic updates that can suffer from slow convergence and counting-to-infinity problems. To speed failure notification and avoid routing loops, they use techniques like route poisoning and hold-down timers. Given Data / Assumptions: A previously reachable route has failed (link down or network unreachable). Neighbors must be informed promptly to stop forwarding traffic along the bad path. We are using a classic distance-vector protocol model. Concept / Approach: With route poisoning, the detecting router advertises the failed network with an infinite metric (for RIP, hop count 16). This “poisons” the route so neighbors immediately mark it unreachable and avoid using that path. Combined with poison reverse and hold-downs, this reduces loops during convergence. Step-by-Step Solution: Detect failure on an interface or via missing updates.Advertise the affected route with metric = infinity (e.g., 16 in RIP).Neighbors propagate the poisoned information, flushing the route from their tables. Verification / Alternative check: Use debug ip rip to observe updates marking the route unreachable; show ip route confirms removal of the prefix after propagation. Why Other Options Are Wrong: Options A and B are unclear and not standard definitions. Option C describes a hold-down timer's purpose, not route poisoning. Common Pitfalls: Confusing route poisoning with split horizon or hold-downs; forgetting that “infinity” is protocol-specific (16 for RIP but different or conceptual for others). Final Answer: It describes when a router sets the metric for a downed link to infinity.

Question 4

Configuring a small network's Internet edge: Given ISP-assigned network 206.143.5.0 for Acme Company and a single gateway router, which set of commands on the gateway would be sufficient to allow Internet access for the site (choose among the listed…

Accepted Answer

Introduction / Context: At a small Internet edge, the minimal requirement for outbound Internet access is a default route on the gateway pointing toward the ISP's next hop. Internal routing protocols may be unnecessary if the site is a single LAN or if internal routers already default to the gateway. Understanding when a static default is sufficient avoids extra complexity. Given Data / Assumptions: Acme has public network 206.143.5.0 and a single gateway to the ISP. ISP next hop is 206.143.5.2 as shown. The question asks which of the listed lines could be configured on the gateway to allow Internet access for the entire network. Concept / Approach: A default route (0.0.0.0/0) on the gateway is sufficient to forward unknown destinations to the ISP. As long as internal hosts know to reach the gateway for off-net traffic (via their default gateway or their own routing), no additional RIP configuration is required on the gateway to send traffic out. Lines 2 and 3 would start RIP and advertise/learn routes, but they are not strictly necessary to achieve outbound access. Line 4 is invalid RIP syntax; originating a default in RIP uses different commands (for example, default-information originate in other protocols, or ip default-network historically) and is not shown correctly here. Step-by-Step Solution: Configure the static default: ip route 0.0.0.0 0.0.0.0 206.143.5.2Ensure inside hosts point to the gateway as their default gateway (or have a route to it).Verify NAT/PAT as required for private addressing (if applicable), and confirm DNS reachability. Verification / Alternative check: From a host, ping/trace to an Internet address; on the gateway, show ip route should list the static default and show ip cef should resolve the next hop. If internal routing is needed, deploy it separately—but not strictly required by this question. Why Other Options Are Wrong: “3 only” (RIP network statement) does nothing alone for Internet access. “1, 2 and 4” includes invalid line 4; starting RIP is unnecessary for simple outbound access. “1 and 4” again includes an invalid command. Common Pitfalls: Assuming a routing protocol is mandatory at the edge; forgetting to configure NAT for private inside networks; misunderstanding that a default route by itself enables outbound traffic if return routing (via ISP) and NAT are in place. Final Answer: 1 only

Question 5

RIPv2 characteristics: Which statement is accurate about Routing Information Protocol version 2 (RIPv2) when compared with RIPv1?

Accepted Answer

Introduction / Context: RIPv2 improves upon RIPv1 primarily by adding classless routing (subnet masks in updates), multicast announcements, authentication, and route tags. However, many core operational aspects—including hop-count metric and default timers—remain unchanged. Recognizing what changed and what did not is a common exam focus. Given Data / Assumptions: Both versions use a maximum hop count of 15 and consider 16 as infinity. The convergence behavior is similar; both are distance-vector with periodic updates. Administrative distance in Cisco IOS defaults to 120 for both RIPv1 and RIPv2. Concept / Approach: RIPv2 retains RIPv1’s update, invalid, holddown, and flush timers (for example, default 30/180/180/240 seconds). The protocol enhancements focus on capability (VLSM, CIDR, multicast 224.0.0.9, authentication), not on changing the fundamental timer model or hop-count metric. Step-by-Step Solution: Compare AD: both are 120 → no advantage for RIPv2.Compare timers: defaults are the same → option about same timers is true.Conclude other statements (faster convergence, lower AD, harder configuration) are not generally true. Verification / Alternative check: Use show ip protocols on a RIPv2 router to see timers; compare with RIPv1 reference—values match by default unless tuned. Why Other Options Are Wrong: Lower administrative distance: incorrect; both are 120. Faster convergence: generally not; both share distance-vector periodic update behavior. Harder to configure: RIPv2 configuration is similar and often simpler due to classless support and multicast. Common Pitfalls: Confusing RIPv2 improvements (VLSM/CIDR, multicast) with performance changes; assuming AD differences where none exist; overlooking authentication support in RIPv2 as a security enhancement. Final Answer: It has the same timers as RIPv1.

Question 6

Routing Fundamentals — Split Horizon (Distance-Vector Loop Prevention) In distance-vector routing (for example, RIP), what is the precise meaning of the split horizon rule?

Accepted Answer

Introduction / Context: Split horizon is a classic loop-prevention technique used by distance-vector routing protocols such as RIP and IGRP. Understanding the exact definition helps you predict which routes are advertised on which interfaces and why certain updates are intentionally suppressed. Given Data / Assumptions: The protocol is distance-vector (for example, RIP). Routers periodically send updates out interfaces. We want to prevent routing information from boomeranging back to its source and creating loops. Concept / Approach: Split horizon states: do not advertise a route back out the interface on which it was learned. This suppresses misleading advertisements that could cause a neighbor to believe you have a better path to a network when your information originally came from that same neighbor. Some implementations extend this with poison reverse, which advertises the route back with an infinite metric to make the suppression explicit. Step-by-Step Solution: Identify the interface on which a route was learned (incoming interface).When generating periodic updates, omit that route on the same outgoing interface (split horizon).Optionally, use poison reverse to send the route back with metric 16 (in RIP) instead of omitting it.Result: neighbors do not re-install a route that would create a loop. Verification / Alternative check: Enable protocol debugging (for example, debug ip rip) on a lab router and observe that routes learned on Serial0 are not re-advertised out Serial0 unless poison reverse is configured. Why Other Options Are Wrong: B: Refers to a physical topology myth; split horizon is not about bus networks. C: Describes update suppression to a downed link, not the learned-on-interface rule. D: Sounds like holddown/poisoning behavior, not the definition of split horizon. E: Summarization is separate (for example, auto-summary in older RIP/IGRP) and unrelated to split horizon. Common Pitfalls: Confusing split horizon with holddown timers or route poisoning; in practice, networks often use a combination of these mechanisms, but their definitions differ. Final Answer: Information about a route should not be sent back in the direction from which the original update came.

Question 7

RIP + Split Horizon — Which Route Will NOT Be Advertised Back to the Neighbor? Given the routing table excerpt below (learned via RIP on Serial0 from neighbor 192.168.40.1), which single network will NOT be advertised back to that same neighbor due …

Accepted Answer

Introduction / Context: Distance-vector protocols periodically advertise routes out interfaces. Split horizon says a router must not advertise a route back out the same interface on which it was learned. This prevents simple routing loops. Given Data / Assumptions: Routes marked R were learned via RIP from 192.168.40.1 on Serial0. Connected networks (C) are locally known and are valid to advertise to neighbors. We are considering advertisements sent back to the same neighbor on Serial0. Concept / Approach: Under split horizon, any prefix learned from a neighbor on an interface is not advertised back out that interface to that neighbor. Locally connected networks (not learned via that neighbor) are eligible to be advertised. Therefore, of the listed options, only the RIP-learned route 192.168.30.0/24 will be suppressed when sending updates back to 192.168.40.1 over Serial0. Step-by-Step Solution: Identify learned-via-Serial0: 192.168.30.0/24 (R via 192.168.40.1).Identify locally connected: 172.16.30.0/24 (Loopback0), 192.168.50.0/24 (Ethernet0), and the link network 192.168.40.0/24.Apply split horizon: suppress only those learned on Serial0 when advertising out Serial0.Conclude the suppressed route is 192.168.30.0/24. Verification / Alternative check: Use debugging (debug ip rip) and observe that locally connected networks are advertised out Serial0, while the route learned from 192.168.40.1 (192.168.30.0/24) is omitted or poisoned depending on configuration. Why Other Options Are Wrong: 172.16.30.0/24 and 192.168.50.0/24 are connected and will be advertised. 192.168.40.0/24 is the transit link itself; its advertisement behavior depends on implementation, but it is not a route learned from the neighbor in question. Claiming “None” ignores split horizon behavior. Common Pitfalls: Assuming all routes are suppressed; only routes learned on that same interface are suppressed, not connected routes or routes learned elsewhere. Final Answer: 192.168.30.0/24

Question 8

Administrative Distance vs. Metric — Why an IGRP Route Beats RIP in the RIB When a network is learned by both RIP and IGRP, why does the routing table install the IGRP route (flagged as IGRP) instead of the RIP route?

Accepted Answer

Introduction / Context: Routers often learn the same destination via multiple routing protocols. The decision process first compares administrative distance (AD), a trust ranking per protocol, before considering metrics. Understanding AD explains why a route from one protocol wins over another in the routing information base (RIB). Given Data / Assumptions: Destination is learned by RIP and IGRP simultaneously. Default AD values: RIP 120, IGRP 100 (lower is preferred). RIB selection: first by AD, then by metric within the same protocol. Concept / Approach: Administrative distance ranks source credibility. Since IGRP's AD (100) is lower than RIP's (120), the router installs the IGRP-learned route and discards the RIP route from the main table (though it may be kept as a backup depending on platform). Metric comparisons matter only within routes from the same protocol; cross-protocol selections never compare RIP hop count with IGRP composite metric. Step-by-Step Solution: List candidate routes grouped by protocol.Pick the group with the lowest AD (IGRP).Within that group, select the best metric (if multiple IGRP paths exist).Install the winning IGRP route in the RIB. Verification / Alternative check: Check platform defaults: show ip protocols shows AD; show ip route displays installed protocol codes and reasons. Changing AD (distance command) can alter selection order. Why Other Options Are Wrong: A: Update timer frequency does not control RIB preference. C/D: Metrics are not compared across protocols; AD decides first. E: Coexistence is common; they can run together. Common Pitfalls: Assuming a “better metric” in RIP can override IGRP; it cannot if AD differs. Final Answer: IGRP has a lower administrative distance.

Question 9

RIP Behavior — Receiving a Higher-Cost Path for an Existing Network Two directly connected routers run RIP. If a router receives an update that advertises a higher-cost (larger hop count) path to a destination that already exists in its routing tabl…

Accepted Answer

Introduction / Context: RIP chooses routes based on minimum hop count. When multiple advertisements for the same prefix arrive, RIP keeps the lowest-hop path. Understanding how RIP treats worse paths helps explain stable behavior and reduces unnecessary churn. Given Data / Assumptions: RIP metric is hop count (lower is better). An existing route with lower hop count already resides in the RIB. A new update arrives with higher hop count. Concept / Approach: RIP installs the best path by hop count. If a newly received advertisement has a worse metric, the router ignores it for route selection. Only if the existing route becomes invalid (for example, times out) or a strictly better metric is learned will the RIB change. Triggered updates and holddown rules further stabilize choices by damping flaps. Step-by-Step Solution: Compare metrics: existing hop count vs. new hop count.If new hop count > existing hop count → mark as worse.RIP ignores worse paths; no RIB replacement occurs.Maintain current entry until a better or valid replacement appears. Verification / Alternative check: Observe with debug ip rip; you will see advertisements received but not installed if their metric is inferior to the current entry. Why Other Options Are Wrong: A: RIP does not keep multiple unequal-cost paths by default (RIPv2 supports equal-cost only). C/D/E: Replacing, deleting, or forcing refresh for a worse path contradicts RIP selection rules. Common Pitfalls: Confusing “higher metric” with “fresher information”; freshness does not override worse metric in RIP. Final Answer: The update will be ignored and no further action will occur.

Question 10

Distance-Vector vs. Link-State — Identify the True Statements Consider the following statements:  Link-state sends its complete routing table out all active interfaces on periodic intervals.  Distance-vector sends its complete routing table out all …

Accepted Answer

Introduction / Context: Routing protocols differ in how they disseminate information. Distance-vector protocols share entire tables periodically, while link-state protocols advertise link-state information (LSAs) and build a full topology locally. Distinguishing these behaviors is vital for predicting convergence and bandwidth use. Given Data / Assumptions: Distance-vector examples: RIP, IGRP. Link-state examples: OSPF, IS-IS. Periodic vs. event-driven updates must be understood correctly. Concept / Approach: Statement 2 is true: distance-vector protocols periodically send their routing tables (in RIP, every 30 seconds). Statement 3 is true: link-state protocols flood link-state advertisements about their own links; routers then compute shortest paths using algorithms like Dijkstra. Statement 1 is false because link-state does not send full routing tables periodically; instead, LSAs are sent on changes and at refresh intervals, not wholesale tables. Statement 4 is false for distance-vector because DV does not send only link states; it sends distance vectors (routes and metrics), not raw link-state data to all routers. Step-by-Step Solution: Classify each statement as DV or LS.Mark 2 (DV periodic full table) as true.Mark 3 (LSA flooding of link states) as true.Mark 1 and 4 as false based on protocol mechanics.Select “2 and 3 only.” Verification / Alternative check: Protocol RFCs and textbooks confirm DV periodic timers and LS flooding mechanisms with separate SPF computations. Why Other Options Are Wrong: 1 only: Misstates link-state behavior. 3 only: Ignores the truth of 2. None: Incorrect because 2 and 3 are true. 1 and 4: Both are false. Common Pitfalls: Assuming link-state sends “routing tables”; it sends LSAs, not computed final routes. Final Answer: 2 and 3 only

Question 11

RIP Metric of 16 — What Does debug ip rip Reveal? You enable debug ip rip and see network 172.16.10.0 being advertised to your router with metric 16. What does a RIP metric of 16 indicate for that route?

Accepted Answer

Introduction / Context: RIP uses hop count as its metric. The protocol defines a maximum of 15 hops; anything beyond that is considered unreachable to prevent routing loops from persisting indefinitely. Given Data / Assumptions: Protocol is RIP (v1 or v2). Metric scale: 1–15 reachable, 16 = infinite (unreachable). debug ip rip shows incoming updates and their metrics. Concept / Approach: A metric of 16 in RIP is the protocol’s representation of infinity. It marks a destination as unreachable, often used in route poisoning to explicitly withdraw a route. This avoids transient loops by ensuring all routers quickly treat the network as down until a valid advertisement appears. Step-by-Step Solution: Observe metric 16 in debug output.Map 16 → “infinite” in RIP metric space.Interpret as an unreachable/poisoned route.Expect neighbors to remove or de-preference the route accordingly. Verification / Alternative check: Check the routing table (show ip route). You should not see a usable path for 172.16.10.0 from that source; if present, it may be via another neighbor at a metric between 1 and 15. Why Other Options Are Wrong: A: 16 hops is beyond RIP’s maximum; the route would be considered unreachable. B: Delay units are not used by RIP (that is an IGRP/EIGRP concept). D: “Messages per second” is unrelated to the metric. E: Summarization length is unrelated to a metric value of 16. Common Pitfalls: Confusing RIP’s metric of 16 with a legitimate distance; it is a sentinel for infinity only in RIP. Final Answer: The route is inaccessible.

Question 12

RIPv2 Loop-Prevention Toolkit — Choose the Mechanisms Used Which of the following mechanisms are used by RIPv2 to help prevent routing loops? (Items: 1) CIDR, 2) Split horizon, 3) Authentication, 4) Classless masking, 5) Holddown timers)

Accepted Answer

Introduction / Context: RIPv2 retains distance-vector fundamentals while adding enhancements like classless routing and authentication. Loop prevention is still critical because DV protocols converge by sharing periodic updates rather than computing from a full topology database. Given Data / Assumptions: We are considering RIPv2 features and general DV loop controls. Candidate mechanisms include split horizon, route poisoning, holddown timers, triggered updates, authentication, and classless support. We must select those specifically aimed at loop avoidance/damping. Concept / Approach: Split horizon suppresses sending a learned route back out the same interface, limiting two-node loops. Holddown timers temporarily ignore worse or conflicting updates after a route is declared down, damping count-to-infinity scenarios. CIDR/classless masking enable classless addressing and summarization (routing correctness/scale) but are not loop-prevention per se. Authentication protects update integrity, not loop mechanics. Step-by-Step Solution: Identify loop-focused controls: split horizon and holddown timers.Exclude CIDR/classless (addressing), and authentication (security), as not directly loop-preventing.Select “2 and 5.”Note: RIPv2 may also use poison reverse and triggered updates, though not listed here. Verification / Alternative check: Protocol references and certification guides list split horizon, holddown, poison reverse, and triggered updates among RIPv2 loop-control techniques. Why Other Options Are Wrong: A/D/E: Include features that do not directly prevent loops (CIDR/classless, authentication). B: Mixes authentication with loop controls; authentication is orthogonal. Common Pitfalls: Assuming authentication prevents loops; it prevents unauthorized or tampered updates but not algorithmic loops. Final Answer: 2 and 5

Question 13

IGRP Path Selection — Default Composite Metric Inputs Which default metric components does IGRP consider when computing the best path to a remote network? (Items: 1) Hop count, 2) MTU, 3) Cumulative interface delay, 4) STP, 5) Path bandwidth value)

Accepted Answer

Introduction / Context: IGRP (the precursor to EIGRP) uses a composite metric that reflects link performance. Knowing which parameters are included by default clarifies why a “shortest-hop” path may lose to a path with higher bandwidth and lower delay. Given Data / Assumptions: IGRP’s composite metric can factor bandwidth, delay, reliability, and load. By default, reliability and load are not active factors. Hop count, MTU, and STP are not default IGRP metric inputs. Concept / Approach: By default, IGRP considers path bandwidth (typically the minimum bandwidth along the path) and cumulative delay (sum of interface delays). These values produce a metric that prefers faster, lower-latency paths even if they traverse more hops. Hop count is a sanity limit but not a metric input. MTU and STP (spanning tree) are irrelevant to IGRP metric calculations. Step-by-Step Solution: List candidate components.Mark bandwidth (5) and delay (3) as default active.Exclude hop count, MTU, and STP as non-metric inputs by default.Select “3 and 5.” Verification / Alternative check: Documentation shows IGRP metric formula incorporating K1bandwidth + K3delay by default (with other K values at zero), confirming bandwidth and delay are the defaults. Why Other Options Are Wrong: A/C/D/E: Include parameters that are not default inputs for IGRP metric calculation. Common Pitfalls: Confusing EIGRP’s extended metric knobs with IGRP’s defaults; although related, defaults still center on bandwidth and delay. Final Answer: 3 and 5

Question 14

Operational Verification — Command That Shows RIP Updates On a Cisco router, which command displays real-time RIP routing updates and advertisements for troubleshooting?

Accepted Answer

Introduction / Context: Troubleshooting routing protocols often requires observing live control-plane messages. Cisco IOS provides debug commands to view protocol activity in real time, which is invaluable when validating neighbors, timers, and advertisements. Given Data / Assumptions: Routing protocol is RIP (v1 or v2). You need to see updates as they are sent/received. Console or vty access with caution (debug can be CPU-intensive). Concept / Approach: The command debug ip rip enables detailed logging of RIP advertisements, including prefixes, metrics, and interfaces. show ip route provides the installed result in the RIB but not the live exchanges. show protocols summarizes interface/protocol status. debug ip route is not a valid command to display RIP updates. Some platforms offer show ip rip database for the learned database, but it still does not show real-time packets like debug. Step-by-Step Solution: Enter privileged EXEC mode.Issue: debug ip ripObserve incoming and outgoing updates in the console.Disable when finished: undebug all or no debug all. Verification / Alternative check: Compare the debug output to packet captures with a SPAN port or embedded packet capture; the updates and metrics will match. Why Other Options Are Wrong: show ip route: Displays results, not live updates. show protocols: Status-only, not update content. debug ip route: Not the correct debug for RIP updates. show ip rip database: Helpful for state, not real-time advertisements. Common Pitfalls: Leaving debug running on production devices; always turn it off to avoid excessive CPU utilization. Final Answer: debug ip rip

Question 15

Classless Routing Protocols — Identify the True Statements Evaluate the following statements about classless routing protocols:  The use of discontiguous networks is not allowed.  The use of variable-length subnet masks (VLSM) is permitted.  RIPv1 i…

Accepted Answer

Introduction / Context: Classless routing protocols carry subnet mask information with each route and support VLSM and discontiguous network designs. Recognizing which protocols are classless helps with address planning and summarization strategies. Given Data / Assumptions: RIPv1 and IGRP are classful and do not include masks in updates. RIPv2, EIGRP, OSPF, and IS-IS are classless and include masks. VLSM requires classless behavior to function across the network. Concept / Approach: Statement 2 is true: classless protocols permit VLSM. Statement 5 is true: RIPv2 is classless and includes mask information in its updates, enabling VLSM and summarization. Statements 1, 3, and 4 are false: classless protocols do allow discontiguous networks, RIPv1 is classful, and IGRP is classful (EIGRP is classless, but the statement cites IGRP). Step-by-Step Solution: Mark VLSM permitted (2) as true.Mark RIPv2 classless (5) as true.Mark the rest as false based on classful/classless definitions.Select the combination “2 and 5.” Verification / Alternative check: Protocol references confirm that only classless protocols carry masks and support VLSM; lab tests with RIPv1 show mask loss across classful boundaries leading to failures. Why Other Options Are Wrong: A/B/E: Include false assertions about classless capability or wrongly label classful protocols as classless. Common Pitfalls: Confusing IGRP (classful) with EIGRP (classless) due to the similar names; always check the “E”. Final Answer: 2 and 5

Question 16

Cisco routing decision scenario: The Corporate router receives an IPv4 packet with source 192.168.214.20 and destination 192.168.22.3. Based on the following 'show ip route' output, what action will the router take?  Corp#sh ip route [output cut] R …

Accepted Answer

Introduction / Context: This question tests how Cisco routers perform a routing table lookup and decide the forwarding action when no matching route exists. Understanding connected routes, learned routes, and default routes is essential for troubleshooting reachability. Given Data / Assumptions: Routing table shows connected networks: 192.168.214.0/24 on FastEthernet0/0 and 192.168.20.0/24 on Serial0/0. Routed (RIP) networks: 192.168.215.0/24, 192.168.115.0/24, 192.168.30.0/24 via 192.168.20.2. No default route is displayed. Packet destination is 192.168.22.3 (network 192.168.22.0/24). Concept / Approach: A router forwards a packet only if it finds a longest-prefix match in the RIB (routing table). If no specific route or default route (0.0.0.0/0) exists, the router drops the packet. The router does not broadcast to discover destinations. Step-by-Step Solution: Identify destination network: 192.168.22.0/24.Check connected routes: 192.168.214.0/24 and 192.168.20.0/24 (no match).Check learned routes: 192.168.215.0/24, 192.168.115.0/24, 192.168.30.0/24 (no match).Check for a default route: none shown.Conclusion: No matching route → drop the packet. Verification / Alternative check: A quick mental match of 192.168.22.0/24 against the entries confirms there is no 192.168.22.0/24 route and no 0.0.0.0/0, so per Cisco behavior the packet is discarded. Why Other Options Are Wrong: Routed out S0/0 or Fa0/0: No route covers 192.168.22.0/24, so no interface selection is possible. Broadcast for the destination: Routers do not broadcast to locate unknown destination networks; they use the RIB. Common Pitfalls: Assuming a router will “try the next-hop for everything” or ARP beyond connected prefixes; without a default route or specific entry, packets are dropped. Final Answer: The packet will be discarded.

Question 17

Static route syntax understanding: For the command ip route 172.16.4.0 255.255.255.0 192.168.4.2, which statements are true?

Accepted Answer

Introduction / Context: This item checks knowledge of Cisco static route configuration and semantics, including administrative distance and the difference between default routes and specific network routes. Given Data / Assumptions: Statement 1: Command establishes a static route. Statement 2: Uses default administrative distance. Statement 3: Configures the default route. Statement 4: The subnet mask refers to the source address. Concept / Approach: The form is ip route . It creates a static route with default administrative distance 1. A default route would use 0.0.0.0 0.0.0.0. The mask applies to the destination network, not a source. Step-by-Step Solution: Check #1: True. This is a static route to 172.16.4.0/24 via 192.168.4.2.Check #2: True. No distance specified → default AD 1 for static.Check #3: False. Default route would be 0.0.0.0/0, not 172.16.4.0/24.Check #4: False. The mask belongs to the destination prefix, not a source. Verification / Alternative check: Show running-config or show ip route static will reveal AD of 1 unless overridden. Why Other Options Are Wrong: Any combination including #3 or #4 is incorrect because the command is not a default route and the mask is not a “source” mask. Common Pitfalls: Confusing source vs destination masks and thinking any ip route equals a default route. Final Answer: 1 and 2

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