350-501 Practice Test 38 — 15 Questions

Question 1

An engineer configures model-driven telemetry on a Cisco XR router to send data to a collector. After configuring, the collector receives no data. The engineer verifies that the collector IP and port are reachable. What is the next step to troubleshoot?

Choose an answer to begin — your selection is scored in the full session.

Accepted Answer

Check that the sensor-group and destination-group are correctly associated and committed in the subscription. In model-driven telemetry on Cisco XR, a subscription must explicitly associate a sensor-group (which defines the data to collect) with a destination-group (which defines where to send it). If these are not correctly associated and committed, the router will not stream any telemetry data to the collector, even if the collector is reachable. The verification of reachability confirms the network path is fine, so the next logical step is to check the subscription configuration.

Answer

Check if the YANG model is valid

Answer

Verify that the router has a route to the collector

Answer

Reboot the router

Answer

Check the SNMP community strings

Question 2

In BGP, what is the purpose of the ORIGINATOR_ID attribute in a route reflector environment?

Accepted Answer

Identifies the originating router to prevent loops. ORIGINATOR_ID is set by the route reflector to identify the originator of the route. It is used to prevent loops in iBGP.

Answer

Indicates the next-hop router

Answer

Sets the local preference

Answer

Identifies the route reflector cluster

Question 3

An SP uses NSO for automation. Which TWO protocols can NSO use as southbound interfaces to communicate with network devices? (Choose two.)

Accepted Answer

RESTCONF. RESTCONF is a southbound interface that NSO uses to communicate with network devices. It is a RESTful protocol that uses HTTP methods (GET, POST, PUT, DELETE) to access YANG-defined data models, making it suitable for modern programmable devices. NSO leverages RESTCONF to configure and manage devices that support this protocol, providing a standardized, stateless interface for automation.

Answer

gRPC

Answer

SNMP

Answer

HTTP

Question 4

Refer to the exhibit. Based on the exhibit, what is the most likely reason for no label bindings?

Accepted Answer

The remote peer has label filtering applied. The exhibit shows that the local router has not received any label bindings from the remote peer (as evidenced by the empty 'show mpls ldp bindings' output), which indicates that the remote peer is not advertising labels. This is typically due to an outbound label filtering policy applied on the remote peer, such as 'mpls ldp neighbor [neighbor-id] label-filter' or 'mpls ldp label-filter' that rejects label advertisements to the local router. The local router's LDP session may be established (based on 'show mpls ldp neighbor'), but the remote peer is actively preventing label distribution.

Answer

The local router has disabled label advertisements

Answer

The IGP routes are not present in the routing table

Answer

The LDP session is not fully established

Question 5

Drag and drop the steps to configure a VLAN on a Cisco switch into the correct order.

Accepted Answer

Step 1: Create VLAN, Step 2: Name VLAN, Step 3: Assign ports to VLAN. VLAN configuration involves creating the VLAN, optionally naming it, and then assigning ports to it.

Answer

Step 1: Assign ports to VLAN, Step 2: Create VLAN, Step 3: Name VLAN

Answer

Step 1: Name VLAN, Step 2: Create VLAN, Step 3: Assign ports to VLAN

Answer

Step 1: Create VLAN, Step 2: Assign ports to VLAN, Step 3: Name VLAN

Question 6

Match each multicast protocol to its role.

Accepted Answer

IGMP: Manages multicast group membership between hosts and local routers. These are essential multicast protocols for service provider IPTV and content delivery.

Answer

IGMP: Builds distribution trees for efficient multicast forwarding

Answer

PIM-SM: Shares active source information between different domains

Question 7

A network architect is designing a Segment Routing (SR) network for a service provider with a requirement for fast convergence upon node failure. The network uses IS-IS as the IGP with segment routing extensions. Which design choice BEST ensures that the network can achieve sub-50ms convergence without relying on any signaling protocol beyond the IGP?

Accepted Answer

Enable TI-LFA (Topology Independent Loop-Free Alternate) on all ISIS interfaces. TI-LFA (Topology Independent Loop-Free Alternate) provides sub-50ms convergence by precomputing backup paths using only the IGP (IS-IS with SR extensions), without requiring any additional signaling protocol. Option A is wrong because BFD with static routes offers fast detection but does not provide a backup path automatically; it must be combined with a protection mechanism like FRR. Option B is wrong because RSVP-TE Fast Reroute relies on RSVP signaling and TE tunnels, which are beyond the IGP-only requirement. Option D is wrong because LDP is a separate signaling protocol that requires LDP FRR and path protection, again adding signaling overhead beyond the IGP.

Answer

Deploy BFD with static routes for fast detection

Answer

Configure RSVP-TE with Fast Reroute on all label-switched paths

Answer

Use LDP with LDP FRR and path protection

Question 8

A service provider is troubleshooting an MPLS L3VPN where customers behind CE-A cannot reach CE-B. The PE routers are Cisco ASR 9000 series. On PE-A, the show cef vrf CUSTOMER prefix 10.1.1.0/24 command displays 'punt' as the forwarding path. What is the most likely cause?

Accepted Answer

The IP prefix is not resolved via an MPLS label in the LFIB. When show cef vrf CUSTOMER prefix 10.1.1.0/24 displays 'punt', it means the prefix does not have a valid MPLS label in the LFIB (Label Forwarding Information Base). In MPLS L3VPN, the PE must push a label for the next-hop PE to forward traffic across the MPLS core. Without a label, the packet is punted to the CPU for further processing, often due to missing label binding or incomplete LDP/IGP synchronization. Option A correctly identifies this issue. Option B is incorrect because MTU issues would cause drops, not punt. Option C is incorrect because missing route-target import would affect route installation in the VRF but not necessarily cause punt for a locally resolved prefix. Option D is incorrect because CE-PE routing protocol (whether OSPF or BGP) is not directly related to MPLS label resolution on the PE.

Answer

The MPLS MTU on the interface is too small

Answer

The VRF is missing the route-target import statement

Answer

The CE is not running OSPF with the PE

Question 9

Refer to the exhibit. An engineer configured a telemetry subscription to push interface state data to a collector. The subscription shows 'State: Invalid'. What is the most likely cause?

Accepted Answer

The collector at 192.168.1.1:57500 is not reachable or the service is down.. The 'State: Invalid' with an associated error such as 'Connection refused' indicates that the subscription cannot reach the collector. This is typically due to the collector not being reachable or the service not listening on the specified port. Therefore, option B is correct. Option A is incorrect because 'encode-kvgpb' is a valid encoding for gRPC telemetry. Option C is incorrect because the xpath '/interfaces/interface/state' is correctly formatted. Option D is incorrect because a periodic update interval of 500 ms is acceptable and not the cause of the invalid state.

Answer

The encoding 'encode-kvgpb' is not supported; must use 'encode-json'.

Answer

The xpath filter is malformed; it should be /interfaces/interface/state.

Answer

The periodic update interval of 500 ms is too fast causing subscription failure.

Question 10

Match each Segment Routing component to its function.

Accepted Answer

SID: A unique identifier for a segment in a segment routing network.. In Segment Routing, SID uniquely identifies a segment, SRGB reserves a label range for global SIDs, and Prefix-SID is a global SID for an IGP prefix. Common confusions include mixing SID with SRGB and Prefix-SID with Adjacency-SID.

Answer

SID: A range of MPLS labels reserved for global segments.

Answer

Prefix-SID: A local SID assigned to a specific adjacency.

Question 11

In the context of network slicing for 5G, which type of slice is optimized for massive IoT with low data rates and high connection density?

Accepted Answer

mMTC. Massive IoT corresponds to mMTC (massive Machine Type Communications) slice, designed for many devices with low data rates.

Answer

uRLLC

Answer

V2X

Answer

eMBB

Question 12

An SP engineer is designing a BGP-based MPLS L3VPN service. The PE routers are fully meshed via iBGP for VPNv4 routes, and an RR is deployed to reduce sessions. The engineer notices that all PE routers are receiving duplicate routes from different PEs, causing suboptimal path selection. Which BGP feature should be enabled to ensure proper load balancing across multiple equal-cost paths?

Accepted Answer

Enable BGP multipath on the PE routers. BGP multipath on PE routers enables the router to install multiple equal-cost paths into the routing table, allowing load balancing across them. In an MPLS L3VPN iBGP full mesh with an RR, duplicate routes are received from different PEs; BGP multipath selects and uses up to the configured number of equal-cost paths. Option A (BGP additional paths) allows advertising multiple paths but does not directly install them. Option B (second RR) reduces sessions but does not affect duplicate routes. Option C (ignoring interior cost) modifies best-path selection but does not enable multipath.

Answer

Enable BGP additional paths on the RR

Answer

Deploy a second RR to reduce the number of iBGP sessions

Answer

Configure the BGP best path selection algorithm to ignore interior cost

Question 13

Based on the exhibit, what is preventing the BGP session from establishing?

Accepted Answer

The TTL security check is blocking the connection. The error message indicates the TTL security check is rejecting the connection because the incoming TTL is not 255 (as expected for an eBGP multihop session). The remote AS is shown as 65000, so it is eBGP. The neighbor is reached via a single-hop but the TTL check expects TTL=255, but the router sees a TTL less than that. Option A is wrong because no MD5 password mismatch is indicated; the error explicitly mentions TTL security. Option B is wrong because the update-source is not the issue; the TTL check is the direct cause. Option C is wrong because the error message does not mention prefix limits; it clearly states TTL security.

Answer

The BGP MD5 password is mismatched

Answer

The BGP update-source is misconfigured

Answer

The neighbor has reached its maximum prefix limit

Question 14

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

Accepted Answer

Video traffic is being dropped at a rate of 5 kbps.. The exhibit shows that the video class has a police rate of 20 kbps and an exceed rate of 5 kbps, indicating that 5 kbps of video traffic is being dropped due to the policer. Option A is false because the voice class has no drops. Option B is false because the policy does not use low-latency queuing (LLQ); it uses policing instead. Option D is false because voice traffic shows zero drops.

Answer

The default class matches only best-effort traffic.

Answer

The policy uses low-latency queuing for voice.

Answer

Voice traffic is experiencing drops due to policer.

Question 15

A service provider uses an MPLS-TE tunnel to carry voice and data traffic. The tunnel is experiencing packet loss during congestion. The engineer wants to ensure that voice traffic receives guaranteed bandwidth and low latency while data traffic uses remaining bandwidth. Which QoS configuration should be applied on the tunnel interface?

Accepted Answer

LLQ with a priority queue for voice and a default class for data. Low Latency Queuing (LLQ) allows you to place voice traffic into a strict priority queue, ensuring guaranteed bandwidth and low latency during congestion, while the default class uses CBWFQ to allocate remaining bandwidth to data traffic. This matches the requirement of prioritizing voice without starving data entirely, as the priority queue is policed to prevent voice from consuming all bandwidth.

Answer

CBWFQ with bandwidth allocation for voice and data

Answer

Policing on voice traffic to limit its rate

Answer

Shaping on the tunnel to 75% of bandwidth with no queuing