350-501 Practice Test 36 — 15 Questions

Question 1

Based on the exhibit, which statement is true about the QoS policy?

Accepted Answer

The VOICE class is allocated a strict priority queue with a bandwidth limit of 10% of the interface bandwidth.. The exhibit shows a QoS policy where the VOICE class is configured with the 'priority' command and a bandwidth statement of 10 percent. In Cisco IOS, the 'priority' command under a class map creates a strict priority queue (LLQ), and the bandwidth percentage defines the maximum amount of interface bandwidth that can be used by this queue, ensuring low-latency treatment for voice traffic. Therefore, option C is correct.

Answer

The class-default will use weighted fair queuing (WFQ).

Answer

The VIDEO class will be limited to 30% of the total interface bandwidth.

Answer

The VIDEO class is guaranteed at least 30% of the total interface bandwidth.

Question 2

In a Segment Routing network with TI-LFA enabled, which mechanism prevents micro-loops during a link failure?

Accepted Answer

Explicit path with segment list and delay timer. In Segment Routing with TI-LFA, micro-loops are prevented by using an explicit path with a segment list and a delay timer. When a link fails, the protecting router installs a backup path with a segment list that steers traffic around the failure, and a delay timer ensures that the backup path is not activated until the network has converged, preventing transient loops.

Answer

Constraint Shortest Path First computation

Answer

Loop-Free Alternate precomputed backup paths

Answer

Prefix Independent Convergence with fast reroute

Question 3

A service provider wants to offer Layer 2 VPN services using MPLS. Which technology should be used to transport Ethernet frames across the MPLS core?

Accepted Answer

Pseudowire. Pseudowire (A) is the correct technology because it provides a point-to-point Layer 2 circuit over an MPLS core, allowing Ethernet frames to be encapsulated and transported transparently. This is defined in RFC 4448 (Ethernet over MPLS) and enables service providers to offer E-Line services. Pseudowire uses MPLS labels to forward frames across the core without requiring the core routers to participate in the customer's Layer 2 control plane.

Answer

LDP

Answer

VPLS

Answer

L3VPN

Question 4

A network engineer is using Cisco NSO to create a managed L3VPN service. After deploying the service, the engineer notices that the configuration on the devices is not being updated. What is the most likely cause?

Accepted Answer

The service has not been committed.. In NSO, services are committed to push configuration changes to devices. If the commit is not performed, the changes remain in the candidate database and are not applied. Other options are less likely given the symptom.

Answer

The service model is not compiled.

Answer

The device is not in the device list.

Answer

The sync-from command was not run.

Question 5

A service provider is deploying multicast over MPLS L3VPN. Which mechanism is used to provide multicast in the core between PE routers?

Accepted Answer

mLDP. In an MPLS L3VPN multicast deployment, the core network between PE routers uses a label-based multicast mechanism rather than a traditional PIM protocol. mLDP (Multipoint LDP) is the correct choice because it establishes point-to-multipoint (P2MP) LSPs in the MPLS core, enabling efficient multicast transport without requiring PIM in the core. This approach is defined in RFC 6388 and is commonly used for MVPN (Multicast VPN) implementations.

Answer

IGMP

Answer

PIM-SM

Answer

PIM-DM

Question 6

During MPLS LDP operation, a router receives a label mapping for a prefix from its neighbor. What is the correct behavior when the receiving router has a route to that prefix?

Accepted Answer

It installs the label as the outgoing label for the prefix.. When a router receives a label mapping from an LDP neighbor for a prefix, it installs the received label as the outgoing label for that prefix in its Label Forwarding Information Base (LFIB). This label is used when forwarding packets toward the neighbor. The router must have a route to the prefix in its routing table to accept the mapping.

Answer

It discards the label mapping unless it has a corresponding route.

Answer

It uses UDP to send a notification back.

Answer

It installs the label as the incoming label for the prefix.

Question 7

A service provider is redesigning its MPLS core to support both L3VPN and L2VPN services. They want to minimize the number of labels in the forwarding table while maintaining per-VRF label allocation. Which label allocation mode should be used for the L3VPN service?

Accepted Answer

Per-VRF label allocation. Per-VRF label allocation assigns a single MPLS label per VRF, meaning all routes within a VRF share the same label. This minimizes the number of labels in the forwarding table compared to per-prefix allocation, while still maintaining per-VRF isolation for L3VPN services. It is the recommended mode when the goal is to reduce label consumption without sacrificing VPN separation.

Answer

Per-CE label allocation

Answer

Per-prefix label allocation

Answer

Per-instance label allocation

Question 8

Which two statements about MPLS label distribution are correct? (Choose two)

Accepted Answer

LDP can establish sessions with non-directly connected neighbors using targeted LDP.. LDP can establish sessions with non-directly connected neighbors using targeted LDP, which uses UDP discovery (port 646) and TCP (port 646) to form a session even when the peers are not directly connected at Layer 3. This is defined in RFC 5036 and is commonly used in MPLS VPN inter-AS options and AToM scenarios.

Answer

RSVP-TE allocates labels based on LDP.

Answer

LDP uses the BGP next-hop as the label FEC.

Answer

TDP is the Cisco proprietary version of LDP.

Question 9

An operator notices that a new MPLS-TE tunnel is not being established. The tunnel configuration includes a dynamic path option and a bandwidth of 100 Mbps. The network uses RSVP-TE with CSPF. The link-state database shows sufficient reservable bandwidth on all links along the calculated path. What is the most likely cause of the tunnel establishment failure?

Accepted Answer

RSVP-TE is not enabled on the transit interfaces. RSVP-TE must be explicitly enabled on every interface that will participate in MPLS-TE label-switched path (LSP) signaling. Even if the link-state database shows sufficient reservable bandwidth, without RSVP-TE enabled on transit interfaces, the PATH messages cannot be processed, and the tunnel will fail to establish. This is a common misconfiguration when deploying MPLS-TE.

Answer

The path option is misconfigured with a strict explicit path

Answer

MPLS LDP is not enabled on the core routers

Answer

The tunnel source interface is not configured with an IP address

Question 10

A network operator uses gRPC Network Management Interface (gNMI) to collect telemetry data from routers. They notice that some updates are missing. Which gNMI mode should be used to ensure that all state changes are captured?

Accepted Answer

ON_CHANGE. ON_CHANGE mode in gNMI ensures that the target device sends a telemetry update immediately whenever a state change occurs, guaranteeing that no updates are missed. This is in contrast to SAMPLE mode, which only sends periodic snapshots and can miss transient changes between intervals. Therefore, to capture all state changes, ON_CHANGE is the correct subscription mode.

Answer

TARGET_DEFINED

Answer

POLL

Answer

SAMPLE

Question 11

A service provider wants to influence inbound traffic from a customer AS. The customer AS is multi-homed to two provider ASes. Which BGP community is most effective to make the customer prefer a specific entry point?

Accepted Answer

Set community 'no-export' on routes from the undesired entry point.. Setting the BGP 'no-export' community on routes from the undesired entry point prevents those routes from being advertised to the customer AS. Since the customer only learns routes from the desired entry point, they will prefer that entry point for inbound traffic. This is a standard technique for influencing inbound traffic without requiring customer-side configuration.

Answer

Set community 'prepend 3' on routes from the desired entry point.

Answer

Set community 'local-preference 200' on routes from the desired entry point.

Answer

Set community 'no-advertise' on routes from the undesired entry point.

Question 12

Which four statements correctly describe the SRv6 micro-SID (uSID) concept? (Choose four.)

Accepted Answer

Micro-SID is incompatible with SR-MPLS.. SRv6 micro-SID uses a compressed SID format where multiple SIDs are encoded in a single 128-bit IPv6 address. It reduces overhead by combining SIDs into a carrier SID. The uSID instruction is usually 16 bits, and the locator block is shared. Micro-SID is incompatible with SR-MPLS because it operates in the IPv6 data plane, whereas SR-MPLS uses MPLS labels.

Answer

Micro-SID requires a dedicated SRH extension header.

Question 13

Which three statements accurately describe the benefits of Segment Routing over RSVP-TE for traffic engineering? (Choose three.)

Accepted Answer

It does not require a signaling protocol like RSVP.. SR-TE reduces state by not requiring per-LSP state on intermediate nodes, supports distributed intelligence via IGP, and does not require a separate protocol like RSVP. However, SR-TE still requires CSPF for path computation, and RSVP-TE also supports fast reroute.

Answer

It provides faster convergence than RSVP-TE FRR.

Answer

It eliminates the need for CSPF path computation.

Question 14

A 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?

Accepted Answer

Apply LLQ for voice and CBWFQ for video and data with bandwidth ratio 2:1.. LLQ provides strict priority queuing for voice (EF), ensuring it is never dropped during congestion, while CBWFQ allows the remaining bandwidth to be shared among video (AF41) and data (AF21) in a 2:1 ratio. LLQ is designed to guarantee low latency for real-time traffic, and CBWFQ enables explicit bandwidth allocation for non-real-time classes. This combination meets the requirement of zero-drop for voice and proportional sharing for video and data.

Answer

Use only LLQ for all three classes.

Answer

Apply CBWFQ with bandwidth percentages to all three classes.

Answer

Use FIFO queuing with WRED for all classes.

Question 15

Which tool can verify connectivity along an MPLS Label Switched Path (LSP) and detect label loops?

Accepted Answer

MPLS LSP ping. MPLS LSP ping is the correct tool because it specifically tests connectivity along an MPLS Label Switched Path by sending MPLS echo request packets that follow the label stack, and it can detect label loops by checking the TTL field in the MPLS header. Unlike regular ICMP-based tools, MPLS LSP ping operates at the MPLS forwarding plane, verifying that the LSP is intact and that labels are correctly swapped at each hop.

Answer

SNMP

Answer

traceroute

Answer

ping