Free Practice Questions for Cisco 400-007 Exam

IP Event Dampening suppresses route flaps caused by unstable interfaces or links:

D: By suppressing frequent route flaps, it reduces unnecessary routing updates and reduces CPU utilization and control plane processing.

E: This suppression stabilizes the overall routing system, especially in large networks where constant recalculation would otherwise occur.

Why other options are incorrect:

A: It does not directly prevent routing loops.

B: It intentionally delays re-advertising to ensure stability, not immediate switching.

C: Detection speed is unaffected; suppression happens after detection.

OSPF throttling timers control the pacing and frequency of SPF calculations and LSA generation. They help strike a balance between fast convergence and control-plane stability. The key timers include:

LSA generation throttling (min/max interval between LSA originations)

SPF calculation throttling (delays between consecutive SPF runs)

By tuning these timers, network designers can:

Prevent CPU overload caused by rapid or repeated LSA updates due to flapping links

Smooth out instability while still enabling responsive convergence

This approach aligns with CCDE v3.1 under “Protocol Design Implications” for optimizing IGP behavior in large, dynamic topologies.

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A (Focus on the solution instead of the problem): While resolving issues quickly is important for operations, solution-oriented thinking during the design phase may overlook essential requirements analysis. Design decisions must be based on problem understanding, traffic analysis, and actual network behavior.

Other options explained:

B, C, D: All directly impact WAN design by influencing QoS, capacity planning, flow optimization, and visibility.

In OSPF multi-area designs with multiple ABRs, when there is temporary inconsistency between the ABRs’ type-3 summary LSAs, microloops can occur during convergence. These loops happen due to slight differences in LSA arrival and SPF calculations across routers while the network is converging.

Microloops are short-lived but can cause brief packet loss.

This becomes more likely as the number of ABRs grows and IGP flooding domains increase.

CCDE v3.1 emphasizes careful ABR design and possible use of loop avoidance mechanisms (e.g., LFA, microloop prevention techniques) in large-scale OSPF designs.

Why other options are incorrect:

A: LSA flooding in OSPF scales well; type-3 LSA replication is not the primary scalability issue.

B: ABRs process all LSAs regardless; load is not split.

D: Multiple ABRs all independently summarize and advertise into the backbone.

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A (TRILL - Transparent Interconnection of Lots of Links):TRILL enables multipathing at Layer 2, eliminating classic STP blocking, allowing all uplinks to be active simultaneously, and uses IS-IS based control plane for conversational MAC learning.

Other options explained:

B: LISP operates at Layer 3 for endpoint mobility, not Layer 2 multipathing.

C: MSTP still blocks some links under normal operation.

D: Switch stacking merges multiple physical switches into one logical switch but does not provide true multipathing across independent switches.

VPLS replicates multicast streams as multiple unicast streams, causing scalability problems with high-bandwidth multicast sources. The most scalable solution is:

Replace VPLS with a Layer 3 MVPN (Multicast VPN): MVPN provides efficient multicast replication in the provider core, dramatically reducing bandwidth consumption compared to Layer 2 replication.

Why other options are incorrect:

A: VPLS handles multicast poorly at scale because of head-end replication.

B: GRE tunnels are operationally complex and do not scale efficiently for large deployments.

C: IGMP snooping may help locally but does not solve replication inefficiency in the core.

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The performance degradation is caused by output queue drops on the 1 Gbps server port. Increasing the queue size allows more data to be buffered during transient congestion periods, preventing packet loss and retransmissions which significantly degrade iSCSI performance.

iSCSI is sensitive to packet loss due to its reliance on TCP.

Increasing the queue depth is a simple, cost-effective method to absorb bursts.

Changing to CIFS (A) is irrelevant since CIFS would suffer similar TCP congestion.

WRED (C) intentionally drops packets during congestion, which is undesirable here.

Enabling TCP Nagle (D) would likely introduce latency and reduce throughput for large data transfers.

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When data center fabrics are extended across multiple private and public clouds, as in hybrid or multi-cloud designs, enterprises benefit from:

C. Ability to place workloads across clouds: Application and workload mobility is a key outcome of interconnected data center fabrics. It supports disaster recovery, scaling, and cost optimization strategies.

D. Centralized visibility: Modern SDN/cloud-integrated platforms offer centralized control and monitoring across domains, giving IT teams end-to-end insight regardless of workload location.

These principles support the CCDE v3.1 goals for cloud-aligned architecture, which promotes flexibility, operational simplicity, and global-scale services.

Why other options are incorrect:

A: Enhanced security is a benefit but not guaranteed simply by interconnecting clouds; it depends on the actual security controls in place.

B: Cloud deployments may compromise data and network ownership, especially in public models.

E: Cloud mobility is typically bidirectional when fully designed; unidirectional behavior is limiting and not an intended design goal.

B (IPFIX telemetry data):IPFIX provides detailed flow-level visibility, enabling identification of traffic patterns, data flows, and destinations. This data is critical for understanding current traffic behavior to identify governance gaps and improve policy compliance.

Other options explained:

A: Secure tunnels protect traffic but do not identify governance gaps.

C: Firewalls provide limited flow visibility compared to telemetry.

D: Workload policies enforce security but do not aid initial visibility analysis.

D (Queue thresholding on the host subinterface):Protects CPU resources by limiting the amount of control plane traffic destined to the router itself.

E (Port filtering on the host subinterface):Allows fine-grained filtering of control plane traffic based on specific protocols or ports, protecting sensitive processes like routing protocols or management access.

Other options explained:

A, B, C: Transit subinterfaces protect forwarding plane transit traffic, not traffic destined to the control plane.