Cisco Certification
59 practice questions with correct answers and detailed explanations. Use this guide to review concepts before taking the practice exam.
The Cisco ENSLD (300-420) certification validates professional expertise in Cisco technologies. This study guide covers all 59 practice questions from our 300-420 practice test, complete with correct answers and explanations to help you understand each concept thoroughly.
Review each question and explanation below, then test yourself with the full interactive practice exam to measure your readiness.
When configuring Cisco SD-WAN, what is the primary purpose of the OMP (Overlay Management Protocol)?
OMP is the control plane protocol in SD-WAN that handles route advertisement, policy distribution, and device reachability information across the overlay network.
Which Cisco Catalyst switching feature provides loop prevention in spanning tree environments?
Root Guard prevents a non-root switch from becoming the root bridge by blocking the port if superior BPDUs are received, maintaining the intended spanning tree topology.
In Cisco SD-WAN, what does the vSmart controller primarily manage?
The vSmart controller is responsible for distributing policies and routes to edge devices, managing the control plane of the SD-WAN overlay.
Which authentication method is most commonly used for 802.1X port security in enterprise networks?
EAP-TLS provides strong mutual authentication using X.509 certificates for both the client and RADIUS server, making it the most secure standard for 802.1X implementations.
What is the primary advantage of using Cisco Catalyst 9000 series switches over legacy platforms?
Catalyst 9000 switches run IOS XE and support model-driven programmability and APIs, enabling automation and software-defined networking capabilities unavailable in legacy platforms.
In a Cisco SD-WAN deployment, what is the purpose of the vEdge router?
vEdge routers are branch devices that terminate overlay tunnels and apply SD-WAN policies to route traffic efficiently across the network overlay.
Which QoS queuing mechanism ensures that latency-sensitive traffic receives guaranteed bandwidth and priority?
CBWFQ with strict priorities guarantees bandwidth to traffic classes while serving high-priority queues before lower-priority ones, ideal for latency-sensitive applications.
What is the primary function of the Cisco vManage dashboard in SD-WAN?
vManage is the centralized management platform offering a GUI for configuration, monitoring, analytics, and troubleshooting of the entire SD-WAN infrastructure.
In Cisco Catalyst switching, what does the term 'stackwise' refer to?
StackWise technology allows multiple Catalyst switches to operate as a single logical device with unified management, simplified configuration, and improved scalability.
Which Cisco Nexus feature provides stateless load balancing across multiple paths with equal cost?
ECMP in Nexus hardware enables stateless load balancing across multiple equal-cost paths, distributing traffic flows without session stickiness requirements.
What is the correct order of spanning tree port states from blocking to forwarding?
The standard spanning tree port state progression is Disabled → Blocking → Listening → Learning → Forwarding, where each state allows progressive participation in the network.
In Cisco SD-WAN, what does the term 'application-aware routing' mean?
Application-aware routing analyzes application types and performance requirements to intelligently select the best path (MPLS, Internet, LTE) for each application.
Which security feature in Cisco Catalyst switches prevents VLAN hopping attacks?
Protected ports prevent trunk negotiation and double-tagging attacks by disabling DTP negotiation and refusing to accept 802.1Q or ISL-tagged frames on access ports.
What is the primary benefit of implementing Cisco SD-WAN over traditional MPLS for branch connectivity?
SD-WAN reduces costs and improves performance by enabling application-aware steering across multiple transports (Internet, MPLS, LTE) with centralized, simplified management.
In a Cisco Nexus environment, what is Virtual PortChannel (vPC) used for?
vPC allows two physical Nexus switches to appear as a single logical switch to downstream devices, enabling redundancy and load balancing without spanning tree blocking.
Which Cisco IOS XE feature allows dynamic adjustment of QoS parameters based on real-time network conditions?
NBAR2 (Network Based Application Recognition) intelligently identifies applications and can dynamically mark traffic with appropriate QoS values based on application requirements.
What is the maximum number of VLAN tags that can be applied to a single frame in 802.1ad (Provider Bridges)?
802.1ad uses double tagging with a Service Provider tag (S-tag) and Customer tag (C-tag), allowing service providers to offer VLAN services while preserving customer VLAN schemes.
In Cisco SD-WAN, how does the system handle traffic when multiple equally good paths exist to a destination?
SD-WAN distributes traffic intelligently across multiple paths based on application requirements, available bandwidth, and path quality metrics to optimize network utilization.
Which Catalyst feature prevents a switch from accepting configuration changes from rogue DHCP servers?
DHCP Snooping validates DHCP messages by maintaining a database of legitimate servers and forwarding only valid DHCP responses through trusted ports.
What is the primary role of the Cisco SD-WAN vBond orchestrator?
The vBond orchestrator serves as the initial point of contact, authenticating devices and facilitating NAT traversal to help SD-WAN devices discover each other and establish tunnels.
In Cisco Nexus data center switches, what does the term 'unified fabric' primarily refer to?
Nexus unified fabric consolidates storage (Fibre Channel) and data network (Ethernet) traffic over unified ports using FCoE, reducing cabling complexity and costs in data centers.
Which QoS marking scheme is most commonly used for end-to-end traffic classification in enterprise networks?
DSCP provides fine-grained, end-to-end QoS classification using six bits in the IP header, supporting 64 different service classes and enabling interoperable QoS across domains.
In a Cisco SD-WAN fabric, what is the primary advantage of using dynamic tunnel establishment over static tunnels?
Dynamic tunnel establishment in SD-WAN automatically creates tunnels on-demand based on traffic flows and adapts to topology changes, eliminating manual tunnel provisioning.
Which Catalyst switching security feature uses RADIUS integration to control per-user port access and permissions?
802.1X uses RADIUS servers to authenticate individual users/devices before allowing port access, enabling granular per-user network access control based on credentials.
In Cisco SD-WAN, what security risk does the Zero Trust architecture address that traditional WAN security does not?
Zero Trust architecture in SD-WAN requires continuous verification of users and devices regardless of location or previous access grants, reducing lateral movement risks from compromised endpoints.
When implementing Cisco SD-WAN, which component is responsible for collecting telemetry data and providing visibility into network performance?
vManage is the management and orchestration platform in Cisco SD-WAN that collects telemetry data, provides dashboards, and enables network visibility and analytics.
Which of the following best describes the primary function of a vBond orchestrator in SD-WAN deployment?
The vBond orchestrator acts as a bootstrap server, facilitating initial device registration, authentication, and secure tunnel establishment between SD-WAN components during deployment.
In a Cisco SD-WAN environment, what is the primary advantage of using TLOC (Transport Locator) in route advertisements?
TLOC identifies a specific combination of device, color (transport type), and encapsulation, enabling intelligent path selection and multi-path optimization in SD-WAN.
Which SD-WAN feature allows organizations to prioritize business-critical applications over less important traffic?
Application-aware routing recognizes applications in real-time and automatically routes them over the best available path based on application requirements and business policies.
When deploying Cisco SD-WAN in a hybrid environment, which protocol is used for secure communication between vSmart controllers and WAN edge devices?
DTLS provides encrypted, connectionless communication between SD-WAN components, enabling secure transmission of control plane traffic in the overlay network.
What is the primary purpose of implementing segmentation in a Cisco SD-WAN network?
SD-WAN segmentation creates isolated network domains based on security requirements, enabling microsegmentation and limiting breach impact through traffic isolation.
In Cisco SD-WAN, which feature enables dynamic traffic steering based on real-time application performance metrics?
SLA-based steering continuously monitors application performance metrics and automatically redirects traffic to alternate paths when SLA thresholds are violated.
Which of the following is NOT a valid transport color option in Cisco SD-WAN?
Cisco SD-WAN defines colors such as MPLS, Internet, Private1, Private2, 3G, LTE, and Satellite. Ethernet is not a transport color; it is a physical layer technology.
What is the recommended approach for ensuring secure device onboarding in a Cisco SD-WAN deployment?
Certificate-based authentication through vBond provides secure, scalable device onboarding with mutual authentication, preventing unauthorized device enrollment.
In SD-WAN, what does the term 'underlay network' refer to?
The underlay network comprises the physical WAN connections (Internet, MPLS, broadband, etc.) that carry the encrypted SD-WAN overlay traffic.
Which Cisco SD-WAN component is responsible for distributing routing policy and forwarding rules to edge devices?
vSmart controllers compute and distribute Overlay Management Protocol (OMP) routes and centralized policies to all WAN edge devices in the network.
What is the primary benefit of implementing quality of service (QoS) in a Cisco SD-WAN environment?
QoS in SD-WAN enables administrators to allocate bandwidth, set traffic priorities, and ensure critical applications receive necessary resources across variable WAN links.
In a multi-region SD-WAN deployment, how are routing decisions made when multiple vSmart controllers are active?
Multiple vSmart controllers in a cluster synchronize routing state and policies to ensure all edge devices receive consistent, coordinated routing decisions.
Which deployment model allows organizations to extend SD-WAN benefits while maintaining existing MPLS infrastructure?
Hybrid SD-WAN enables organizations to add broadband and internet transports to existing MPLS networks, providing cost savings while leveraging current infrastructure investment.
What is the purpose of implementing rate limiting policies in Cisco SD-WAN?
Rate limiting policies control how much bandwidth specific applications or users can consume, ensuring equitable resource distribution and preventing network congestion.
In Cisco SD-WAN, which feature provides protection against unauthorized access to control plane communications?
Mutual certificate-based authentication combined with DTLS encryption secures control plane communications between all SD-WAN components, preventing spoofing and eavesdropping.
What does the OMP (Overlay Management Protocol) accomplish in a Cisco SD-WAN network?
OMP runs on top of DTLS and distributes routes, policies, and service information across the SD-WAN overlay, creating a logical network independent of physical topology.
Which SD-WAN deployment scenario would benefit most from zero-trust architecture principles?
Large distributed enterprises with numerous branch and remote user access points benefit most from zero-trust SD-WAN, enabling fine-grained segmentation and continuous verification.
In Cisco SD-WAN, what is the function of a WAN edge device (vEdge or Catalyst)?
WAN edge devices terminate IPsec tunnels to other edges, enforce local policies, perform application identification, and make forwarding decisions based on vSmart-distributed rules.
Which approach is most effective for monitoring and troubleshooting SD-WAN performance issues in real-time?
vManage provides real-time dashboards, performance metrics, historical analytics, and alerting capabilities, enabling proactive SD-WAN network monitoring and rapid issue resolution.
What is the primary advantage of using a centralized SD-WAN management approach versus distributed management?
Centralized management through vManage enables consistent policy deployment, simplified configuration updates, improved visibility, and reduced operational complexity at scale.
In a Cisco SD-WAN deployment, how does application identification and routing differ from traditional WAN routing?
SD-WAN performs deep packet inspection (DPI) to identify applications and routes them based on policies tied to application type and performance requirements, not just destination IP.
What is the recommended practice for disaster recovery in a multi-controller Cisco SD-WAN environment?
Geographically distributed, synchronized vSmart and vManage controllers provide automatic failover, high availability, and resilience without manual intervention or single points of failure.
Which factor is most critical when designing an SD-WAN network to support business-critical applications?
Proper SD-WAN design requires understanding SLA requirements for critical applications and implementing corresponding quality metrics, path selection policies, and backup mechanisms.
When implementing Cisco Catalyst 9000 series switches in an enterprise network, which feature enables real-time visibility into application performance and network health?
Cisco DNA Center with Assurance provides AI-driven, real-time visibility into application performance and network health across the enterprise, replacing traditional monitoring approaches.
In a software-defined WAN (SD-WAN) deployment, what is the primary advantage of using centralized policy management compared to device-by-device configuration?
Centralized policy management in SD-WAN allows organizations to enforce consistent policies across all sites from a single point, dramatically reducing configuration complexity and enabling rapid policy updates.
Which encryption protocol is recommended for securing management access to Catalyst 9000 switches in compliance with modern security standards?
SSH version 2 provides encrypted management access and is the industry standard for secure remote device management, replacing legacy protocols like Telnet.
When designing a network using Cisco's intent-based networking principles, which component is responsible for translating business intent into network policies?
Cisco DNA Center serves as the central intelligence platform that translates high-level business intent into actionable network policies that are automatically deployed across the infrastructure.
In implementing 802.1X network access control, what is the role of the RADIUS server in the authentication process?
The RADIUS server validates user credentials submitted by the supplicant and provides the authenticator (switch) with authorization decisions to permit or deny network access.
Which security feature in Cisco Catalyst switches helps prevent spoofing attacks by verifying the legitimacy of incoming frames at Layer 2?
Dynamic ARP Inspection and DHCP Snooping work together to validate Layer 2 address bindings and prevent ARP spoofing and DHCP starvation attacks.
What is the primary benefit of implementing Cisco DNA Spaces in an enterprise environment?
DNA Spaces leverages device location and behavioral analytics to deliver personalized experiences, guest management capabilities, and proactive security insights across the enterprise.
In a network undergoing digital transformation with Cisco solutions, which framework ensures that security is embedded throughout the architecture rather than added as an afterthought?
Cisco's Zero Trust security framework, integrated within intent-based networking, ensures continuous verification and microsegmentation at every layer rather than trusting internal networks.
When deploying Cisco ISE (Identity Services Engine) in an enterprise, what critical function does it perform in the network security posture?
Cisco ISE is the identity and access management platform that enforces granular security policies based on user identity, device compliance, and network context.
In implementing network segmentation using micro-segmentation principles, which technology from Cisco enables application-level granularity in access control policies?
Cisco TrustSec uses Security Group Tags to enable application-aware, identity-based micro-segmentation that moves beyond IP-based network segmentation to provide true application-level granularity.
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