Deploying Cisco Service Provider Advanced Network Routing Free Practice Test — 30 Questions

Question 1

A Tier-1 service provider is experiencing intermittent but severe packet loss and elevated latency on a critical inter-domain peering link with a major content delivery network (CDN). This is directly impacting several high-profile enterprise customer services. The network engineering team has been alerted and must provide a resolution within a tight timeframe. Which of the following approaches best demonstrates the necessary technical proficiency and behavioral competencies to effectively address this complex, high-pressure situation?

Accepted Answer

Systematically analyze BGP routing stability, interface statistics for errors and discards on both ends of the peering, and conduct targeted packet captures to identify specific packet drops or retransmissions, while maintaining open communication with the CDN's network operations team for collaborative troubleshooting.

Question 2

A service provider\'s core aggregation router is exhibiting intermittent connectivity issues impacting several large enterprise clients. Initial troubleshooting points to BGP route flapping, leading the network operations team to temporarily increase BGP dampening timers on the affected device. While this has somewhat stabilized the immediate symptoms, it has raised concerns about potential suboptimal traffic engineering and prolonged convergence times for legitimate route changes. Considering the need for a robust and sustainable solution, what is the most prudent next step to address this complex network instability?

Accepted Answer

Conduct a detailed analysis of BGP neighbor states and traffic patterns to identify the root cause of the flapping and evaluate the impact of the current dampening configuration.

Question 3

Consider a multi-VRF BGP-MPLS VPN deployment where PE1 advertises a VPNv4 route learned from CE1 (located in AS 65001) to PE2. The advertisement from PE1 to PE2 includes the Route Target extended community \'65001:100\' and a Route Origin attribute indicating an iBGP learned path. PE2 has a VRF named \'CUSTOMER_A\' configured to import routes with the Route Target \'65001:100\'. Assuming no other specific import or export policies are in place on PE2 that would prevent this, what is the most accurate outcome regarding the route\'s installation into VRF \'CUSTOMER_A\' on PE2?

Accepted Answer

PE2 will install the VPNv4 route into VRF 'CUSTOMER_A' because the advertised Route Target matches the VRF's import configuration.

Question 4

A service provider, AS 65001, has two direct BGP peering relationships: one with AS 65002 and another with AS 65003. Both peers provide transit for a specific customer\'s IP prefix, 192.0.2.0/24. Network engineers in AS 65001 need to ensure that all outbound traffic from their network destined for 192.0.2.0/24 is directed through AS 65002, even though AS 65003 is also a valid path. Which BGP attribute should be manipulated, and how, to achieve this specific traffic engineering objective within AS 65001?

Accepted Answer

Increase the Local Preference for routes to 192.0.2.0/24 learned from AS 65002.

Question 5

A large-scale service provider network is experiencing severe BGP instability, manifesting as rapid prefix flapping and significant packet loss across multiple interconnected Autonomous Systems. Initial diagnostics reveal that the issue began shortly after the implementation of a new, complex BGP policy on a set of route reflectors designed to optimize traffic engineering. The network operations team is struggling to pinpoint the exact cause due to the intricate dependencies between the new policy, existing traffic engineering mechanisms (like MPLS-TE tunnels and BGP communities used for path selection), and the sheer volume of routing information being processed. The situation demands immediate action to restore stability, but also a methodical approach to prevent recurrence. Which of the following strategies best addresses the immediate need for stability while laying the groundwork for a permanent solution, reflecting the behavioral competencies of adaptability, problem-solving, and leadership potential in a high-pressure, ambiguous environment?

Accepted Answer

Implement a phased rollback of the new BGP policy on route reflectors, concurrently analyzing BGP peer states and traffic engineering path metrics for anomalies, while establishing clear communication channels with affected engineering teams to report progress and coordinate further actions.

Question 6

A network operations team at a large telecommunications provider is investigating persistent route flapping for a critical customer prefix announced via BGP. Analysis of the network topology reveals that a static route, configured with a lower administrative distance than the default BGP administrative distance, is being redistributed into the BGP routing table. This static route\'s next-hop is intermittently becoming unreachable due to a separate, unrelated network issue. When the static route’s next-hop is available, it is preferred over the dynamically learned BGP routes for the same prefix. However, when the static route’s next-hop becomes unavailable, the static route is withdrawn, leading to the customer prefix’s BGP advertisement being withdrawn. Upon restoration of the static route\'s next-hop, the prefix is re-advertised. This cycle is causing significant instability. Which of the following actions would most effectively resolve this route flapping issue by ensuring the stability of BGP path selection for this prefix?

Accepted Answer

Increase the administrative distance of the redistributed static route to a value higher than the default BGP administrative distance.

Question 7

Anya, a senior network engineer for a global telecommunications provider, is alerted to a critical transit link between two major Points of Presence (PoPs) exhibiting intermittent packet loss and elevated latency, impacting several high-priority customer services. The link is a high-capacity fiber optic connection actively managed by BGP for traffic engineering. Anya suspects the issue might stem from an interaction between dynamic routing convergence events and the link\'s Quality of Service (QoS) implementation, rather than a simple physical layer fault. Considering the advanced nature of the network and the potential for subtle misconfigurations, which troubleshooting strategy would most effectively isolate the root cause and guide remediation efforts in this scenario?

Accepted Answer

Systematically analyze BGP route advertisements and received attributes for instability or suboptimal path selection on the affected routers, cross-referencing these findings with real-time interface statistics for utilization, discards, and error counters, while simultaneously reviewing the configured QoS policies, particularly traffic shaping and queuing mechanisms, for any anomalies that could manifest as intermittent packet drops under load.

Question 8

A service provider\'s network operations center (NOC) is alerted to a persistent issue where a specific customer\'s /24 IPv4 prefix is repeatedly advertised and then withdrawn from BGP tables by multiple peers, causing intermittent connectivity. This behavior is not observed for other customer prefixes or across the provider\'s broader network. The NOC team has ruled out physical link failures on their core infrastructure and confirmed that the customer\'s edge device is online. What is the most probable underlying cause for this specific route flapping scenario, demanding immediate attention for service restoration?

Accepted Answer

Inconsistent or misconfigured BGP session timers and keepalive intervals between the service provider and its peering partners, leading to premature session resets and route re-advertisements.

Question 9

A service provider is deploying a BGP confederation to manage its large network infrastructure, consisting of member ASes 50000, 50001, and 50002. The confederation\'s external peer is AS 60000, which advertises a critical prefix. The network operations team needs to ensure that all traffic originating from within AS 50000 and destined for this prefix preferentially traverses through member AS 50001. Which BGP attribute should be manipulated on the confederation boundary router of AS 50000 to achieve this specific outbound traffic engineering goal, assuming standard BGP path selection rules are in effect and no complex policy routing or route reflectors are being utilized for this particular inter-AS path influence?

Accepted Answer

LOCAL_PREF

Question 10

A Tier-1 service provider observes recurring periods of elevated packet loss and latency impacting a key enterprise customer\'s connectivity. Network telemetry indicates that the primary path, typically utilizing a segment of the backbone, is experiencing unpredictable congestion. The operations team needs to implement a routing strategy that can automatically adapt to these dynamic conditions, ensuring traffic is steered towards available, lower-latency paths without requiring manual configuration changes for each micro-burst event. Which routing protocol feature set is most crucial for addressing this operational challenge and maintaining service continuity?

Accepted Answer

Link-state routing with traffic engineering extensions for dynamic path computation based on real-time link metrics.

Question 11

A major telecommunications provider is experiencing intermittent packet loss and increased latency across its core network, directly impacting several high-profile enterprise clients who rely on guaranteed Quality of Service (QoS) for their mission-critical applications. Initial diagnostics reveal no single, obvious hardware failure or configuration error. The network operations center (NOC) is following its standard troubleshooting playbook, but the problem persists and appears to be evolving, suggesting a complex interaction within the BGP control plane or inter-domain routing policies that are not immediately apparent. The pressure is mounting as client service level agreements (SLAs) are being breached. Which of the following actions best reflects the necessary blend of technical acumen and behavioral competencies to effectively manage this escalating situation?

Accepted Answer

Prioritizing the establishment of a rapid, cross-functional incident response team with clearly defined roles, empowered to deviate from standard operating procedures based on real-time telemetry analysis, and initiating immediate, transparent communication with affected clients regarding the nature and expected resolution timeline of the disruption.

Question 12

A service provider\'s network engineering team has recently initiated a migration from an established Interior Gateway Protocol (IGP) to a more modern, segment-routing-centric control plane for its MPLS backbone. Post-deployment in a critical core region, intermittent packet loss and routing instability are being reported by multiple downstream customers. Initial diagnostics have not pinpointed a clear cause, and the pressure to restore full service is mounting. Which of the following actions best demonstrates the required behavioral competencies of adaptability and flexibility in managing this unforeseen network disruption?

Accepted Answer

Immediately initiate a full, network-wide rollback to the previous IGP and halt all further migration activities until the root cause is definitively identified and resolved.

Question 13

Anya, a network engineer for a large telecommunications provider, is investigating a recurring issue where a specific customer\'s IP prefix is intermittently disappearing and reappearing in the service provider\'s BGP routing table and subsequently in its advertisements to other peers. The BGP peering session with the customer\'s edge router remains stable, with no declared failures or resets. The customer reports no changes to their internal routing or network configuration. Anya has confirmed that the issue is not related to physical layer problems or general network congestion. Considering the advanced nature of BGP deployments in service provider networks and the specific symptom of a single prefix exhibiting instability while the overall session is healthy, what is the most likely underlying cause of this intermittent route flapping?

Accepted Answer

Dynamic modification of BGP route advertisement policies based on fluctuating community attributes, enforced via route maps.

Question 14

A critical inter-AS link connecting AS 65001 to AS 65002 experiences an unexpected failure. The primary path for latency-sensitive applications between these autonomous systems utilized this link. The only available alternate path traverses a secondary inter-AS link that, due to its geographical routing, inherently introduces a higher propagation delay. Within AS 65001, OSPF is the interior gateway protocol. The service provider must ensure that latency-sensitive traffic continues to meet its stringent jitter and delay Service Level Agreements (SLAs) despite the primary link outage. What is the most effective strategy for the network operator within AS 65001 to prioritize the handling of this critical traffic over the secondary link, considering the inherent delay difference?

Accepted Answer

Decreasing the OSPF cost associated with the secondary inter-AS link.

Question 15

During the deployment of a novel traffic engineering solution utilizing advanced segment routing principles within a critical Tier-1 service provider backbone, engineers encounter persistent, intermittent packet loss and route instability that defy initial diagnostic efforts. The established troubleshooting playbook, designed for more predictable network behaviors, is proving ineffective, and the operational impact is escalating. The team lead, facing significant pressure from network operations and executive management, must guide the team through this complex and uncertain situation. Which of the following actions best demonstrates the required behavioral competency to navigate this scenario effectively?

Accepted Answer

Initiate a comprehensive review of all protocol configurations, concurrently explore alternative diagnostic tools and methodologies, and proactively engage with the vendor for insights into potential edge cases or undocumented behaviors of the new routing technology.

Question 16

A large metropolitan service provider is experiencing sporadic BGP route instability for a critical customer prefix originating from an upstream provider. This instability is causing intermittent connectivity issues for the customer. While investigating, the network operations team identifies that one of the upstream providers is intermittently withdrawing and re-advertising the prefix, causing BGP next-hop changes and traffic shifts. The provider has multiple upstream connections, and one of them remains stable and consistently advertises the prefix. How should the network operations team configure BGP to prioritize traffic destined for this customer\'s prefix through the stable upstream connection, thereby minimizing service disruption, without impacting the routing of other prefixes?

Accepted Answer

Increase the local preference for BGP routes learned from the stable upstream provider for the customer's prefix.

Question 17

A service provider\'s core router, running BGP, receives two distinct inbound advertisements for the same destination prefix from an external network via two different peering sessions with AS 65001. The router\'s internal BGP configuration has set specific attributes for each advertisement to influence path selection. Consider the following attribute values for each path:

Path A: Weight = 300, Local Preference = 100, AS_PATH = 65001 65002, Origin = IGP, MED = 150
Path B: Weight = 100, Local Preference = 100, AS_PATH = 65001 65003, Origin = EGP, MED = 100

Given these configurations, which path will the BGP process ultimately select for forwarding traffic to the destination prefix?

Accepted Answer

Path 1

Question 18

A service provider is implementing a new, complex BGP policy designed to optimize traffic flow for a high-priority financial services client. During the rollout, a secondary, but still critical, e-commerce client begins experiencing intermittent packet loss, directly correlating with the activation of the new policy. Analysis of the network telemetry reveals that the route-reflector configuration, in conjunction with specific attribute manipulation within the new policy, is causing this degradation for the e-commerce segment. The technical team has a rollback plan, but a complete reversion would negate the benefits for the financial client. What is the most effective immediate course of action to address this situation, balancing technical resolution with client satisfaction and operational continuity?

Accepted Answer

Implement a targeted rollback of the specific BGP route-reflector configuration causing the packet loss for the e-commerce client, while communicating the issue and resolution steps to both clients.

Question 19

A service provider is multi-homed to two different upstream Internet Service Providers (ISPs), ISP-Alpha and ISP-Beta. The provider wishes to engineer inbound traffic from ISP-Alpha to predominantly enter their network via the edge router connected to ISP-Alpha\'s primary fiber optic link, while ensuring that traffic from ISP-Beta enters via their respective connection without specific inbound preference engineering from ISP-Beta\'s perspective. Considering the standard BGP path selection process and the typical attributes used for traffic engineering between Autonomous Systems, which of the following actions would best achieve the stated objective for inbound traffic from ISP-Alpha?

Accepted Answer

Advertise routes to ISP-Alpha via the primary link with a lower MED value compared to any routes advertised via secondary links to ISP-Alpha.

Question 20

Anya, a senior network engineer at a large telecommunications company, is tasked with troubleshooting a newly established BGP peering session with a partner network. Since the activation of this peering, the company has observed a significant increase in packet loss and elevated latency on critical customer traffic traversing this inter-domain link. Anya suspects that the issue stems from a misconfiguration or a mismatch in routing policies between the two networks. Considering the advanced nature of service provider routing and the potential for subtle BGP attribute manipulation or policy conflicts to impact performance, what would be Anya\'s most effective initial strategic approach to diagnose and rectify the problem while minimizing further service impact?

Accepted Answer

Conduct a detailed review of the BGP session configuration, specifically examining advertised and received path attributes, community tags, and route policies applied to the peering, cross-referencing these against the established peering agreement and internal traffic engineering objectives.

Question 21

Anya, a senior network engineer at a large ISP, is troubleshooting a persistent issue where customers on a specific subnet are experiencing intermittent packet loss and elevated latency on their primary internet egress path. Initial investigations reveal that the BGP path to the destination network via an upstream transit provider is showing increased jitter and occasional route flapping. The network utilizes complex BGP policies and is part of a multi-homed environment with several upstream providers. Which of Anya\'s proposed strategies would most effectively address the underlying routing instability and restore optimal performance, demonstrating an understanding of advanced service provider routing principles?

Accepted Answer

Manipulate BGP attributes, such as AS-PATH prepending or community-based route selection, on internal BGP sessions to influence traffic away from the degraded path towards a more stable alternative route.

Question 22

A service provider\'s core network is experiencing intermittent BGP session instability between two critical routers, R1 and R2, connected via a private leased line. BGP neighbors are observed to go down and then re-establish every few hours, causing temporary routing disruptions. Network monitoring indicates that packet loss on the leased line, while generally low, occasionally spikes above 5% for short durations. The current BGP timer configuration is the default. Which of the following actions would most effectively address and mitigate this BGP neighbor flapping issue?

Accepted Answer

Increase the BGP Keepalive and Holdtime intervals to 90 and 270 seconds, respectively.

Question 23

A service provider\'s network is experiencing sporadic BGP route flapping for a critical customer prefix, leading to intermittent connectivity issues. The BGP sessions themselves remain established, and the customer\'s edge routers show no signs of instability. Analysis of the routing information reveals that the provider\'s internal policies are influencing the `LOCAL_PREF` for this prefix, aiming to direct inbound traffic through a specific peering point. However, the customer also advertises the same prefix to the provider via a secondary peering point, utilizing a lower Multi-Exit Discriminator (MED) value to influence their own inbound traffic. When minor, transient disruptions occur in the provider\'s internal Interior Gateway Protocol (IGP) convergence, the BGP path selection for the customer\'s prefix oscillates. Which of the following strategies would most effectively resolve this route flapping while adhering to service provider routing best practices and maintaining customer traffic engineering control?

Accepted Answer

Implement a consistent, monotonically increasing MED policy for the customer's prefix across all provider ingress points, ensuring it is higher than any MED the customer might advertise, and maintain a high LOCAL_PREF on the primary ingress.

Question 24

An edge router within a Tier-1 Internet Service Provider\'s network receives multiple BGP updates for the prefix 198.51.100.0/24. Analyze the following inbound BGP attribute information for each path and determine which path the router will install into its routing table, assuming no explicit route policies or peer-group configurations are influencing the decision beyond standard BGP best-path selection criteria:

Path A: Received from neighbor 192.168.1.1 (AS 65001), AS_PATH: 65001 65002, Local Preference: 200, Weight: 100
Path B: Received from neighbor 192.168.2.2 (AS 65003), AS_PATH: 65003 65004, Local Preference: 150, Weight: 0
Path C: Received from neighbor 192.168.3.3 (AS 65005), AS_PATH: 65005 65006, Local Preference: 200, Weight: 0

Which path will be selected for the prefix 198.51.100.0/24?

Accepted Answer

Path A

Question 25

A service provider\'s MPLS VPN service experiences sporadic packet loss during peak hours, particularly when there are frequent changes in VPN membership or routing policy. Initial diagnostics show stable link utilization and no interface errors, but the loss correlates with bursts of BGP updates and LDP session re-negotiations. The provider\'s network relies heavily on BGP VPNv4 route exchange and LDP for label distribution. Which of the following control plane phenomena is most likely contributing to the observed packet loss, given the dynamic nature of the network and the symptoms described?

Accepted Answer

Inefficient BGP attribute propagation and LDP label binding convergence leading to temporary forwarding inconsistencies.

Question 26

A Tier-1 service provider experiences a sudden and severe degradation in network performance, characterized by frequent route flaps and elevated CPU utilization on its core edge routers. Investigation reveals a new, large-scale Internet exchange point (IXP) peer has initiated full BGP routing table exchange, significantly exceeding the capacity of the existing infrastructure to process the rapid influx of prefixes. This is directly impacting customer traffic. Which of the following strategies would be the most prudent and effective initial response to stabilize the network while a more comprehensive long-term solution is developed?

Accepted Answer

Implement a BGP inbound route-map on the IXP peering session, permitting only a predefined, manageable subset of essential prefixes and a maximum route count.

Question 27

Anya, a network engineer for a global telecommunications provider, is investigating a sudden surge in customer complaints regarding degraded performance on an MPLS VPN service. Initial diagnostics indicate intermittent packet loss and elevated latency, particularly affecting real-time applications. Upon reviewing recent network changes, Anya identifies the deployment of a new Quality of Service (QoS) policy on several Provider Edge (PE) routers designed to enhance video conferencing traffic. However, the issue appears to be exacerbated during periods of peak network utilization. What is the most appropriate immediate action and subsequent strategic approach for Anya to resolve this complex network degradation, demonstrating adaptability and sound technical judgment?

Accepted Answer

Temporarily roll back the recently deployed QoS policy to stabilize the service, then meticulously re-engineer the QoS configuration with a focus on optimized buffer allocation and queue scheduling algorithms to accommodate traffic fluctuations and prevent congestion-related packet drops.

Question 28

Anya, a senior network engineer at a large telecommunications provider, is investigating a reported issue of intermittent packet loss and increased latency on a critical MPLS backbone link connecting two major aggregation sites. Users are experiencing degraded performance for real-time services. The network is configured with OSPF for interior gateway routing and BGP for inter-AS peering, with MPLS labels distributed via LDP. While no complete link failures are reported, the link\'s performance metrics show sporadic spikes in packet drop rates and round-trip times. Which of the following diagnostic approaches would most effectively address the immediate cause of these observed symptoms?

Accepted Answer

Analyze interface statistics for CRC, input, and output errors on the routers at both ends of the affected link.

Question 29

A service provider, AS65000, has established peering with two different upstream transit providers, AS200 and AS300. Both AS200 and AS300 are advertising the same destination prefix originating from AS100 to AS65000. AS65000 needs to engineer traffic such that AS100 preferentially sends traffic destined for AS65000\'s network through AS200, rather than AS300. Assuming all other BGP attributes (AS-PATH length, origin, community strings, etc.) are equal or have been normalized to be neutral for this decision, what specific manipulation of BGP attributes should AS65000 implement on its advertisements *to* AS200 and AS300 to achieve this preferential inbound traffic flow from AS100?

Accepted Answer

Advertise the prefix to AS200 with a lower MED value than the MED value used when advertising to AS300.

Question 30

Anya, a senior network engineer at a major telecommunications provider, is troubleshooting persistent quality degradation in real-time services across their backbone network. Customers report choppy audio and video interruptions during periods of high network utilization. Initial diagnostics reveal that while link utilization is not consistently at capacity, routing paths are dynamically changing in ways that introduce variable latency. The current routing configuration prioritizes shortest path convergence and administrative preference, with no explicit consideration for jitter or latency sensitive applications. Considering the need to maintain service level agreements (SLAs) for premium traffic, which of the following strategic adjustments to the routing policy would best address the observed issues while demonstrating adaptability to evolving network demands?

Accepted Answer

Implement dynamic traffic engineering policies that leverage latency and jitter metrics to influence path selection for real-time traffic flows.

Deploying Cisco Service Provider Advanced Network Routing Free Practice Test — 30 Questions

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