350-501 Practice Test 21 — 15 Questions

Question 1

Which MEF service type provides a point-to-point Ethernet connection between two user-network interfaces (UNIs)?

Accepted Answer

E-Line. MEF (Metro Ethernet Forum) defines E-Line as a point-to-point Ethernet service that connects exactly two UNIs, providing a dedicated Ethernet Virtual Connection (EVC) between them. It is the MEF equivalent of a leased line or Ethernet private line, and is used for site-to-site connectivity.

Answer

E-LAN

Answer

E-Tree

Answer

E-Access

Question 2

A 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?

Accepted Answer

Low-latency queueing (LLQ) with a policer. Low-latency queueing (LLQ) combines strict priority scheduling with a policer to limit the priority queue's bandwidth. This ensures voice traffic is always transmitted first while preventing the priority queue from consuming all available bandwidth, which would starve other queues. The policer enforces the 500 Mbps limit, meeting both requirements for real-time voice.

Answer

Traffic shaping with a token bucket and no priority queue

Answer

Weighted random early detection (WRED) with explicit congestion notification

Answer

Class-based weighted fair queueing (CBWFQ) with bandwidth guarantee

Question 3

A service provider is implementing QoS on a PE router for customer traffic. Which tool should be used to classify traffic based on application layer information?

Accepted Answer

MQC with NBAR. NBAR (Network-Based Application Recognition) is a deep packet inspection (DPI) engine within the Modular QoS CLI (MQC) that can identify applications by inspecting payloads up to Layer 7. This allows classification of traffic based on application-layer information such as HTTP, DNS, or proprietary protocols, which is exactly what the question requires.

Answer

Access-list

Answer

Shaping

Answer

Policy-map with police

Question 4

A network administrator needs to automate the deployment of a new QoS policy on dozens of provider edge routers. Which Cisco tool is best suited for this purpose?

Accepted Answer

Cisco Network Services Orchestrator (NSO). Cisco Network Services Orchestrator (NSO) is the correct tool because it provides model-driven orchestration and automation for deploying and managing network configurations across hundreds of devices using YANG data models and NETCONF. For QoS policy deployment, NSO can push consistent service definitions (e.g., class-maps, policy-maps, service-policy) to multiple provider edge routers simultaneously, ensuring compliance and reducing manual errors.

Answer

Cisco SecureX

Answer

Cisco Prime Infrastructure

Answer

Cisco ISE

Question 5

Which TWO access technologies are considered fiber-based solutions for service provider access networks? (Select two.)

Accepted Answer

XGS-PON. GPON and XGS-PON are fiber-based PON technologies.

Answer

WiMAX

Answer

Cable (DOCSIS)

Answer

DSL

Question 6

A service provider has a network with PE1, P1, P2, and PE2 connected in a chain: PE1-P1-P2-PE2. The IGP is IS-IS with wide metrics, and MPLS LDP is enabled on all interfaces. The goal is to provide L3VPN services between PE1 and PE2. The engineer has configured MP-iBGP between PE1 and PE2, and the VPNv4 routes are exchanged. However, when a CE router behind PE1 tries to reach the CE behind PE2, the traffic fails. The engineer checks the MPLS forwarding table on PE1 and sees that the label for the BGP next-hop (PE2's loopback) is 'Untagged'. The BGP next-hop is reachable via ICMP. What is the most likely cause of this issue?

Accepted Answer

LDP is not enabled on the interface between PE1 and P1.. The MPLS forwarding table on PE1 shows the label for PE2's loopback as 'Untagged', which indicates that LDP has not assigned a label for that prefix on the incoming interface. Since LDP is responsible for distributing labels for IGP routes (like loopbacks) in an MPLS LDP-enabled network, the missing label means LDP is not operational on the link between PE1 and P1. Without a label, PE1 cannot push an MPLS label for the BGP next-hop, causing the VPNv4 traffic to be dropped or forwarded as IP, which fails because the core routers (P1, P2) do not have the VPN route.

Answer

The IS-IS metric between PE1 and P1 is too high, causing suboptimal routing.

Answer

The MPLS TTL propagation is disabled, causing packets to be dropped.

Answer

The MTU on the link between PE1 and P1 is set to 1500, causing fragmentation.

Question 7

A service provider is implementing network automation using YANG data models. They need to ensure that the automation solution supports both configuration and operational state data retrieval. Which NETCONF operation should be used to retrieve operational state data?

Accepted Answer

. The NETCONF operation retrieves both configuration and operational state data from a device, making it the correct choice for this requirement. Unlike , which only returns configuration data, accesses the running datastore and includes state data such as interface statistics, routing tables, and system status. This aligns with RFC 6241, where is defined as the operation to retrieve combined config and state information.

Answer

<edit-config>

Answer

<get-config>

Answer

<lock>

Question 8

A service provider wants to prevent BGP hijacking by validating the origin AS of received routes. They deploy RPKI with Route Origin Authorizations (ROAs). When a router receives a prefix with an origin AS that matches the ROA, what is the BGP Origin Validation state?

Accepted Answer

Valid. If the prefix and origin AS match a ROA exactly, the validation state is 'valid'. If no ROA is found, it's 'not-found'. If there is a mismatch, it's 'invalid'.

Answer

Invalid

Answer

Unknown

Answer

Not-found

Question 9

An ISP is designing an MPLS core network and needs to choose an IGP that supports fast convergence. Which IGP meets this requirement and is most commonly used in MPLS core networks?

Accepted Answer

IS-IS. IS-IS is the correct choice because it is a link-state IGP that inherently supports fast convergence through mechanisms like incremental SPF (iSPF) and prefix-independent convergence (PIC). It is widely deployed in MPLS core networks due to its scalability, extensibility via TLVs, and native support for MPLS Traffic Engineering (MPLS-TE) without requiring additional protocol extensions like OSPF's opaque LSA.

Answer

OSPFv3

Answer

EIGRP

Answer

RIPng

Question 10

Which OSPF adjacency type requires DR/BDR election on a multi-access network?

Accepted Answer

Non-broadcast. Both broadcast and non-broadcast multi-access (NBMA) networks require DR/BDR election in OSPF to reduce the number of adjacencies. Point-to-point and point-to-multipoint networks do not use DR/BDR.

Answer

Point-to-multipoint

Answer

Point-to-point

Question 11

An SP network engineer configures IS-IS with wide metrics. Which statement is true about IS-IS wide metrics compared to narrow metrics?

Accepted Answer

Wide metrics use Type-Length-Value (TLV) extensions to carry traffic engineering information.. Wide metrics use a 24-bit field, allowing values up to 16,777,215, and support TE extensions and segment routing.

Answer

Narrow metrics are required for IPv6 routing in IS-IS.

Answer

Wide metrics are only supported in Level 1 routing.

Answer

Narrow metrics support up to 63 cost values, while wide metrics support up to 255.

Question 12

A service provider is using MPLS L3VPN with BGP as the PE-CE routing protocol. A customer reports that routes from one site are not being installed in the VRF of another site. The engineer verifies that the PE routers have established BGP sessions with the CEs and that the VPNv4 routes are being exchanged between PEs. Which configuration element must be verified to ensure that the customer routes are imported into the correct VRF?

Accepted Answer

The route target (RT) import and export settings on the PE routers.. In MPLS L3VPN, route targets (RTs) are used to control the import and export of VPNv4 routes between VRFs. Each VRF is configured with import and export RTs. When a PE router exports a route from a VRF, it attaches the export RT as a BGP extended community. The receiving PE router compares the RT on the route with the import RTs configured in its VRFs. If there is a match, the route is imported into the corresponding VRF. Therefore, incorrect RT configuration is a common cause of routes not being installed in the target VRF.

Answer

The BGP cluster ID on the route reflectors.

Answer

The route distinguisher (RD) on the PE routers.

Answer

The MPLS LDP label binding for the loopback interfaces.

Question 13

An engineer is using NETCONF to retrieve the operational QoS statistics from a router. The response contains XML data but does not include the queueing statistics. What is the most likely reason?

Accepted Answer

The NETCONF filter did not include the correct YANG path for QoS statistics. NETCONF retrieves data based on YANG models. If the filter does not specify the correct YANG path for QoS queueing statistics, the server will not include that data in the response. The YANG data model for QoS (e.g., Cisco‑IOS‑XE‑qos‑oper.yang) defines specific paths for queueing counters; omitting or mis‑specifying the filter path results in an incomplete reply.

Answer

The user does not have enough privilege level

Answer

The statistics are only available via SNMP

Answer

The router is running an older IOS that does not support NETCONF

Question 14

Which MPLS EXP bits value is typically mapped from DSCP EF at the ingress PE to maintain voice QoS in an MPLS network?

Accepted Answer

EXP 5. DSCP EF (Expedited Forwarding, DSCP 46) is typically mapped to MPLS EXP bit value 5 at the ingress PE to preserve voice QoS. This mapping ensures voice traffic receives priority treatment across the MPLS backbone. EXP 5 corresponds to the highest priority for low-latency, low-jitter traffic.

Answer

EXP 3

Answer

EXP 7

Answer

EXP 0

Question 15

Which THREE of the following are benefits of using Segment Routing over LDP in an MPLS network? (Choose three.)

Accepted Answer

Enables traffic engineering without RSVP-TE.. Option A is correct because Segment Routing can steer traffic along explicit paths using segment lists (SR policies) without deploying RSVP-TE, since the path is encoded in the packet header rather than signaled hop-by-hop. Option B is correct because SR leverages existing IGP (IS-IS or OSPF) extensions to distribute segment identifiers, removing the need to run a separate label-distribution protocol like LDP alongside the IGP. Option C is correct because with SR the IGP itself distributes SID/label information and traffic engineering is handled via SR policies, so LDP and RSVP-TE can be eliminated from the core. Option D is not a benefit of SR over LDP, as neither protocol provides inherent protection against label spoofing; that requires separate mechanisms. Option E is incorrect because SR does not require BGP-LU for label distribution—labels come from IGP-advertised SIDs, and BGP-LU is an independent mechanism used for inter-domain scenarios.

Answer

Provides inherent security against label spoofing.

Answer

Requires BGP-LU for label distribution.