Be able to explain NSO's NED abstraction and MQC structure, and configure class-maps, policy-maps, and service-policies for DSCP or precedence marking. The key is knowing which component matches traffic versus which component acts on it.
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Domain overview
This domain covers Cisco NSO service orchestration and MQC-based QoS on service provider networks. Questions test how NSO talks to devices via NEDs and protocols such as NETCONF, CLI, and SNMP, plus how MQC class-maps, policy-maps, and service-policies classify, mark, and shape traffic using DSCP and IP precedence.
Exam objectives
How NSO uses NEDs to abstract device types and communicate via NETCONF, CLI, or SNMP
MQC class-map match criteria such as DSCP, IP precedence, ACL, and NBAR
Policy-map actions including marking, policing, shaping, and queueing in service-policies
Applying QoS service-policies to interfaces and verifying with show policy-map interface
Confusing the NED with the NSO core or CDB; the NED is the per-device-type driver, not the orchestrator or data store
Assuming NSO only speaks NETCONF; many NEDs use CLI, SNMP, or vendor APIs depending on the device
Mixing class-map match criteria with policy-map actions, or attaching a policy-map directly to an interface instead of a service-policy
Click any question to see the full explanation and answer options, or start a focused practice session above.
In the DiffServ model, which DSCP value is used for Expedited Forwarding (EF) to support voice traffic?
2An SP network uses NSO for service orchestration. Which component in NSO provides the abstraction layer to communicate with different device types using protocols like NETCONF or CLI?
3What is the primary difference between traffic policing and traffic shaping?
4An SP engineer is implementing LLQ on a PE router to prioritize voice. Which additional configuration is recommended to prevent voice traffic from starving other queues?
5In the context of YANG modeling for network automation, which statement about 'must' expressions is true?
6An SP uses NSO with a YANG service model to provision an L3VPN. The service model references a leafref to a VPN ID that must exist in a separate list. Which YANG statement ensures the leafref value is valid against the referenced list?
7Which MQC component is used to match traffic based on criteria such as DSCP or IP precedence?
8An SP router is configured with CBWFQ. For a data class requiring 30% bandwidth guarantee, which command is correct in the policy-map?
9When automating service provisioning with NSO, which three components are part of the NSO architecture? (Choose three.)
10Which DSCP value is recommended for Expedited Forwarding (EF) per-hop behavior, commonly used for voice traffic?
11A service provider wants to enforce a hard rate limit of 10 Mbps on a subscriber's traffic, dropping any excess packets. Which QoS mechanism should be used?
12In an SP network using NSO for service orchestration, which component abstracts device-specific CLI or SNMP interactions into a common model for NETCONF/RESTCONF southbound communication?
13Which NETCONF RPC is used to retrieve the complete running configuration from a network device?
14A service provider is implementing hierarchical QoS on an edge router. The goal is to shape the aggregate traffic to 100 Mbps and then apply different queuing policies for voice and data within that shaped pipe. Which configuration approach is correct?
15In the MQC (Modular QoS CLI) framework, which component is used to match traffic based on DSCP values?
16An SP network operator needs to ensure that voice traffic always gets priority access to the output link. Which queuing mechanism is designed to provide a strict priority queue while preventing starvation of other queues?
17In SR-PCE architecture, which protocol is used for communication between the Path Computation Element (PCE) and the Path Computation Client (PCC) to request and report SR-TE paths?
18When DSCP markings are mapped to MPLS EXP bits at the ingress PE router, how many EXP values are available for traffic differentiation in the MPLS core?
19A service provider is designing a QoS policy for a business VPN service that carries voice, video, and data. The policy must ensure that voice (EF) is never dropped even during congestion, while video (AF41) and data (AF21) share the remaining bandwidth in a ratio 2:1. Which queuing strategy should be used?
20In NSO, which statement best describes the function of the CDB (Configuration Database)?
21Which congestion avoidance mechanism is used to prevent tail drop by selectively dropping packets from lower-priority flows before the queue becomes full?
22A service provider wants to use NETCONF to manage devices. Which two statements are true about NETCONF operations? (Choose two.)
23Which three mechanisms are used within the DiffServ model to provide QoS in an SP network? (Choose three.)
24A service provider is deploying a QoS policy for a customer with voice, mission-critical data, and best-effort traffic. The voice requires strict priority and low latency. Which queuing mechanism should be used to ensure voice packets are always served before other queues, and what additional measure is necessary to prevent voice traffic from starving other traffic?
25In the DiffServ model, which DSCP value is used for Voice over IP (VoIP) traffic to ensure Expedited Forwarding (EF) per-hop behavior?
26In SP automation, which protocol is used by NSO to communicate with network devices for configuration management?
27An SP uses traffic policing and shaping to manage bandwidth. Which statement best describes the difference between the two mechanisms?
28In the context of MPLS QoS, at which point are EXP bits typically set based on the DSCP value of the IP packet?
29An SP uses SR-PCE for traffic engineering. Which protocol does the SR-PCE use to communicate path computation requests and responses with path computation clients (PCCs)?
30In the DiffServ model, which per-hop behavior (PHB) is associated with the AF31 DSCP value?
31Which YANG data modeling construct is used to restrict a leaf value to be a reference to another leaf in the data tree?
32In the Modular QoS CLI (MQC), which component is used to define traffic classes based on match criteria?
33An SP engineer is designing a QoS policy for a customer with three traffic classes: voice (priority), premium data (bandwidth guarantee), and best effort. The total bandwidth is 10 Mbps, with voice limited to 1 Mbps, premium data to 4 Mbps, and best effort to the remaining. Which policy-map configuration correctly uses LLQ and CBWFQ?
34Which two statements correctly describe the use of DSCP values in the DiffServ model? (Choose two.)
35Which three components are part of NSO (Network Services Orchestrator) architecture? (Choose three.)
36A service provider is implementing QoS for voice traffic using the DiffServ model. Which DSCP value should be assigned to voice packets to ensure the highest priority treatment?
37In MPLS networks, the EXP bits are used for QoS. How are the 3-bit EXP values typically derived from DSCP markings at the ingress PE router?
38Which NETCONF operation is used to retrieve the entire running configuration from a network device?
39An SP is deploying SR-TE policies using PCEP. What is the role of the SR-PCE in this architecture?
40An engineer configures a class-map to match traffic with DSCP AF41. What is the numerical DSCP value for AF41?
41In a hierarchical QoS policy, the parent policy shapes to 20 Mbps. The child policy has a class for voice with priority and police rate 2 Mbps, and a class for data with bandwidth 10 Mbps. What is the maximum bandwidth voice traffic can consume under congestion?
42What is the primary function of the NED (Network Element Driver) in NSO?
43Which RESTCONF HTTP method should be used to replace the entire configuration of a device interface?
44What is the main difference between traffic shaping and traffic policing?
45Which TWO statements correctly describe the DiffServ model? (Choose two.)
46An SP is designing MQC policies. Which THREE statements about MQC are true? (Choose three.)
47An SP uses NSO for automation. Which TWO protocols can NSO use as southbound interfaces to communicate with network devices? (Choose two.)
48Which DSCP value is used for voice traffic (EF) in the DiffServ model?
49Which MPLS EXP bits value is typically mapped from DSCP EF at the ingress PE to maintain voice QoS in an MPLS network?
50An SP is designing a QoS policy for a customer with voice, video, and data traffic. Which queuing mechanism provides a strict priority queue for voice while ensuring other queues do not starve?
51In a hierarchical QoS policy applied to a subscriber aggregation interface, the parent policy shapes to 100 Mbps and the child policy allocates 50% bandwidth to voice and 50% to data. If voice traffic exceeds 50 Mbps, what happens to the excess?
52Which protocol is used by NSO to communicate with network devices for configuration management?
53An SP engineer is using YANG to model a service. Which statement correctly describes the use of a 'leafref' type?
54In the context of SR-PCE, which protocol does the PCE use to communicate with the path computation client (PCC) to set up SR-TE policies?
55Which DSCP value corresponds to Best Effort (DF) per-hop behavior?
56An SP uses NSO with a YANG service model to provision L3VPNs. Which database in NSO stores the configuration and state for all managed devices?
57What is the primary difference between traffic shaping and policing in a QoS implementation?
58Which component in MQC is used to classify traffic based on match criteria?
59Which THREE statements are true regarding NSO's NED? (Choose three.)
60Which TWO methods can RESTCONF use to create a new data resource? (Choose two.)
61An SP is designing a QoS policy for a customer VPN that carries voice, video conferencing, and bulk data. The voice traffic requires low latency, video conferencing requires assured bandwidth, and bulk data should use any remaining bandwidth. Which queuing strategy should be applied on the PE-CE link?
62An SP is deploying SR-TE policies using a central controller. The controller needs to compute paths based on bandwidth and latency constraints. Which protocol is used between the controller and the routers to signal the SR-TE policies?
63An SP network engineer is reviewing a QoS configuration on a PE router. The policy-map uses a class for voice with the 'priority' command, and a class for video with 'bandwidth remaining percent 30'. What is the purpose of the 'bandwidth remaining percent' command?
64In the DiffServ model, which field is used in the IP header to mark packets for QoS treatment?
65An SP engineer is designing a QoS policy for a business customer with three traffic classes: Voice (critical latency), Transactional Data (low delay), and Bulk Data (no strict requirements). The link is 100 Mbps. Which TWO actions should be part of the policy? (Select two.)
66An SP is deploying a Network Services Orchestrator (NSO) for service automation. Which THREE components are integral to NSO architecture? (Select three.)
67A service provider is deploying a QoS policy on a Cisco ASR 9000 Series Router. The network engineer must ensure that real-time voice traffic receives strict priority scheduling and that the priority queue is limited to 500 Mbps to prevent starvation of other queues. Which QoS mechanism should be configured to meet these requirements?
68A service provider is using Cisco NSO (Network Services Orchestrator) to automate the deployment of MPLS L3VPN services. The network engineer needs to ensure that the NSO service model can dynamically allocate route distinguishers (RDs) and route targets (RTs) for each VPN instance. Which NSO component is responsible for generating these unique identifiers based on service input parameters?
Be able to explain NSO's NED abstraction and MQC structure, and configure class-maps, policy-maps, and service-policies for DSCP or precedence marking. The key is knowing which component matches traffic versus which component acts on it.
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