700-841 Sample Questions & Answers

Cisco's Resilient Ethernet Protocol (REP) is specifically designed for fast convergence in ring topologies, typically achieving sub-50ms failover times. This makes it ideal for critical infrastructure like traffic control systems where downtime must be minimized. Standard STP has convergence times of 30-50 seconds, and RSTP is faster at 1-2 seconds, but neither meets the sub-50ms requirement. HSRP is a first-hop redundancy protocol for gateways, not a Layer 2 ring resiliency protocol.

The Cisco URWB solution (based on Fluidmesh technology) uses a patented 'make-before-break' roaming algorithm. This means a mobile unit establishes a connection to the next radio access point before disconnecting from the current one. This seamless handoff ensures continuous connectivity and is designed to achieve zero packet loss, which is critical for applications controlling moving machinery. While other options contribute to a robust network, 'make-before-break' is the specific feature that addresses the zero-loss handoff requirement.

High-availability Seamless Redundancy (HSR) and Parallel Redundancy Protocol (PRP) are both defined by the IEC 62439-3 standard and are designed for zero-loss failover. PRP works by sending duplicate frames over two independent parallel networks, while HSR sends duplicate frames in opposite directions around a ring. Both ensure that at least one copy of the frame arrives even if a link or node fails, providing the seamless redundancy required for critical control applications. REP and DLR provide fast recovery, but not necessarily zero-loss failover.

VPN Segmentation is the core feature in Cisco SD-WAN used to create logically isolated routing domains. The engineer would configure one VPN for OT traffic, which is tunneled to the data center, and another VPN for IT traffic. Policies can then be applied to the IT VPN to allow for a local internet breakout. Application-Aware Routing is used for path selection based on performance, not for foundational segmentation.

Edge Intelligence uses Data Policies to define the flow and transformation of data. Within the Data Policy, you can apply scripts (typically in JavaScript) to manipulate the data as it passes from the southbound source to the northbound destination. This is where logic such as scaling values, changing data types, or restructuring JSON payloads is implemented.

The most effective and automated method is to integrate Cyber Vision with Cisco Identity Services Engine (ISE) via pxGrid. When Cyber Vision detects a threat, it can publish this information to ISE. ISE can then take an automated action, such as assigning the offending HMI to a quarantine Security Group. The ISA 3000, being SGT-aware, will enforce a policy associated with this quarantine SGT, effectively isolating the device or blocking its traffic. This provides a closed-loop, automated threat response.

The core of the Cisco URWB solution is the Fluidity technology, which uses a multiprotocol label switching (MPLS)-like mechanism over the wireless medium. It intelligently routes packets across the best available path in the mesh network on a per-packet basis. This allows it to dynamically route around interference and congested links, ensuring high reliability and optimal performance even in noisy RF environments.

This scenario describes a classic use case for REP combined with a management platform. Resilient Ethernet Protocol (REP) provides the fast-converging, fault-tolerant ring topology. Cisco IoT Field Network Director (FND) or a similar management platform like DNA Center provides the centralized management, allowing the network of switches to be provisioned, monitored, and managed as a cohesive system. While other options provide redundancy or simplified management, this combination specifically addresses both requirements for a distributed industrial network.

Device templates in Industrial Asset Vision are used to standardize and simplify the configuration of large numbers of similar sensors. A template can define common settings like the data reporting frequency, alert thresholds (e.g., high/low temperature), and other operational parameters. Associating a sensor with a template during onboarding automatically applies this configuration, saving significant time and reducing the risk of manual errors.

DPI goes beyond standard Layer 3/4 firewalls by inspecting the payload (Layer 7) of industrial protocol packets. This allows the security solution (like Cyber Vision or an ISA 3000) to understand the specific commands being sent (e.g., 'Read Register', 'Stop PLC') and the data being transferred. This deep visibility is crucial for asset discovery, detecting anomalous behavior, and creating granular security policies that permit legitimate operations while blocking malicious or unauthorized commands.