350-501 Practice Test 20 — 15 Questions

Question 1

An SP engineer is configuring model-driven telemetry (MDT) to monitor interface utilization on Cisco routers. The telemetry receiver uses gRPC and is experiencing high CPU load due to excessive subscription data. Which MDT subscription parameter should be adjusted to reduce the data rate without losing critical threshold events?

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

Accepted Answer

Enable on-change reporting with suppression.. On-change reporting with suppression reduces data rate by sending updates only when values change, and suppression prevents too-frequent updates. Increasing sample interval risks missing threshold events. Other options do not effectively reduce data rate while preserving event detection.

Answer

Use a smaller path XPath.

Answer

Increase the sensor-group period.

Answer

Increase the sample-interval.

Question 2

What is the primary benefit of using model-driven telemetry over traditional SNMP polling for network assurance?

Accepted Answer

Provides real-time data streaming without polling overhead. Model-driven telemetry uses a push model where network devices continuously stream structured data (e.g., YANG-encoded) to a collector, eliminating the need for periodic SNMP polling. This provides real-time visibility with minimal CPU overhead on the device, as the device itself initiates the data export based on configured subscriptions, rather than responding to repeated GET requests.

Answer

Reduces the need for YANG models

Answer

Increases security by using SSH

Answer

Simplifies device configuration

Question 3

A network administrator is configuring a Cisco ASR 9000 router for MPLS L3VPN. The PE receives customer routes via eBGP from the CE. Which command is required to redistribute these routes into the VPNv4 BGP table on the PE?

Accepted Answer

Configure 'address-family ipv4 unicast' under the VRF configuration and then 'address-family vpnv4 unicast' under the BGP process.. In MPLS L3VPN, customer routes learned via eBGP from the CE must be placed into the VRF's IPv4 unicast table first, and then the 'address-family vpnv4 unicast' under BGP is required to redistribute those VRF routes into the VPNv4 BGP table, which carries the route with its route distinguisher (RD) and extended community. This two-step process ensures the PE can advertise the route as a VPNv4 prefix to other PEs via MP-BGP.

Answer

Configure 'address-family ipv4 vrf CUSTOMER' under the BGP process and activate the neighbor.

Answer

Enter 'vrf CUSTOMER' in the BGP process and then 'address-family ipv4 unicast' under the VRF.

Answer

Enter 'redistribute bgp 100' under the VRF's OSPF or static route configuration.

Question 4

A network engineer is configuring an MPLS L3VPN on a PE router. The VRF is configured with route-target import/export. The PE and CE are running eBGP. The CE advertises routes to the PE, and the PE installs them in the VRF routing table. However, the remote PE does not receive these routes via BGP VPNv4. The local PE's BGP table shows the VPNv4 prefixes with the correct next hop and label. The remote PE's BGP table shows no such prefixes. The IGP between the PEs is working, and MPLS LSPs are up. What is the most likely cause and correct action?

Accepted Answer

Check the route-target import/export configuration on both PEs and ensure they match. Despite the local PE having the routes in BGP VPNv4, the remote PE does not receive them. This often indicates that the route-target export on the local PE does not match the route-target import on the remote PE, or that the VPNv4 session is not correctly configured. Since the local PE shows the prefixes in its BGP VPNv4 table, they are being advertised to the BGP peer, but the remote PE's import policy filters them due to mismatched RT. The correct action is to verify the route-target configuration on both PEs.

Answer

Enable the 'soft-reconfiguration inbound' command

Answer

Reset the BGP session between the PEs

Answer

Check the MTU on the link between the PEs

Question 5

A service provider offers Carrier Ethernet services using MPLS-TP in the access and aggregation layers. The network uses MPLS-TP tunnels with static LSPs and protection via 1:1 linear protection with APS. One customer reports intermittent connectivity issues on their E-LINE service. The operations team observes that the protection switchover is occurring frequently due to apparent signal failures on the working path. However, the physical layer shows no errors. The protection switching is configured with revertive mode. The working LSP has an RDI (Remote Defect Indication) configured. Upon further investigation, the team finds that the working LSP's OAM continuity check messages (CCMs) are being lost occasionally, triggering a protection switch. What is the most likely misconfiguration?

Accepted Answer

The CCM interval is too short, causing frequent false failures due to transient congestion.. A short CCM interval makes the system sensitive to minor delays, causing false failures and frequent protection switches. A longer interval would reduce sensitivity but increase detection time. Priority and OAM rate differences are not typical causes.

Answer

The CCM interval is too long, causing delayed detection.

Answer

The working path uses a higher MPLS-TP OAM rate than the protection path.

Answer

The protection path has a lower priority than the working path.

Question 6

A large SP is using model-driven telemetry to collect interface statistics from 5000 routers to a centralized collector. The collector is deployed on two servers with load balancing. Recently, the operations team noticed that some router telemetry streams are missing data for intervals of up to 5 minutes during peak hours. The engineer suspects packet loss between the routers and collector. The routers are sourced from different vendors but all support gRPC dial-out telemetry. The engineer wants to identify which routers are affected. The current configuration uses a single telemetry collector IP with port 5000. What step should the engineer take to isolate the problematic routers?

Accepted Answer

Check the telemetry subscription statistics on each router for drops and errors.. Checking telemetry subscription statistics on each router (e.g., using show telemetry statistics) provides per-router counters for drops, errors, and sequence gaps. This directly identifies which routers are experiencing loss. Other options are either too manual, network-wide, or do not isolate individual routers.

Answer

Use a packet capture on the network to identify drops.

Answer

Enable telemetry debugging on each router and review logs.

Answer

Configure a second collector on a different port and split the routers across two collectors.

Question 7

Given the output, which configuration mismatch would prevent a remote PE in the same VPN from installing this route into its VRF?

Accepted Answer

The remote PE has an import RT that does not include RT:65000:200.. The route carries RT:65000:200. For a remote PE to install this route into its VRF, the VRF must have an import RT that includes RT:65000:200. If the remote PE's VRF imports a different RT (e.g., RT:65000:100), the route will not be installed. Option B is incorrect because different route distinguishers (RDs) do not prevent route installation as long as the Route Target matches. Option C is incorrect because MPLS VPN does not filter routes based on BGP AS-path by default; moreover, the AS-path containing AS 65000 is not a typical filter in this context. Option D is incorrect because the next-hop 10.1.1.2 is reachable in the remote PE's global routing table, as indicated by the output (or assumed reachable).

Answer

The remote PE uses a different route distinguisher for its VRF.

Answer

The remote PE filters routes based on BGP AS-path containing AS 65000.

Answer

The next-hop 10.1.1.2 is not reachable in the remote PE's global routing table.

Question 8

A service provider is planning to offer L2VPN services using MPLS. Which TWO statements are true regarding Ethernet over MPLS (EoMPLS) and Virtual Private LAN Service (VPLS)?

Accepted Answer

EoMPLS provides a point-to-point pseudowire between two PE routers.. EoMPLS (Ethernet over MPLS) is correct because it establishes a point-to-point pseudowire (Martini draft, RFC 4448) between two PE routers, transporting Layer 2 Ethernet frames across an MPLS core without MAC learning or multipoint capabilities.

Answer

VPLS requires all PE routers to be in the same VLAN.

Answer

VPLS uses a hub-and-spoke topology to interconnect multiple sites.

Answer

EoMPLS supports MAC address learning between sites.

Question 9

Which TWO tasks are required when implementing segment routing in an MPLS network?

Accepted Answer

Configure the IGP (OSPF or IS-IS) with segment routing extensions. Options C and D are correct. Configuring the IGP (OSPF or IS-IS) with segment routing extensions is essential to advertise prefix-SIDs and adjacency-SIDs, enabling segment routing control plane. Enabling MPLS on all interfaces that participate in segment routing forwarding is required to enable MPLS forwarding for the SIDs. Option A (RSVP-TE) is not required because segment routing uses source-routed paths instead of RSVP-TE LSPs. Option B (CEF) is generally enabled by default on Cisco routers and is a prerequisite for MPLS forwarding, but it is not a task specific to implementing segment routing. Option E (LDP) is not required because segment routing replaces LDP with SID-based label distribution.

Answer

Configure RSVP-TE to establish LSPs

Answer

Enable CEF on all routers

Answer

Enable LDP on all routers and interfaces

Question 10

Refer to the exhibit. An operator configures an SR-TE policy on a headend router. Which statement is true about the traffic steered into this policy?

Accepted Answer

The headend will impose a label stack containing labels 16000, 16001, and 16002. The SR-TE policy uses a segment-list with three labels (16000, 16001, 16002), which are MPLS labels assigned to prefix-SIDs for specific nodes. The headend imposes this label stack to steer traffic along the explicit path defined by the segment-list, ensuring strict source routing without relying on dynamic CSPF computation or LDP.

Answer

The segment-list consists of adjacency-SIDs

Answer

The path is automatically computed using CSPF based on IGP metrics

Answer

Traffic is forwarded using MPLS LDP labels

Question 11

Which THREE are common causes of QoS misconfiguration on PE routers? (Choose three.)

Accepted Answer

Applying a policy-map in the wrong direction (input vs output).. Applying a policy-map in the wrong direction (input vs output) is a common QoS misconfiguration because QoS actions like shaping, policing, and queuing are direction-specific. For example, shaping is typically applied on the egress interface to control outbound traffic, while policing can be applied inbound to rate-limit incoming traffic. Misapplying a policy-map (e.g., attaching a shaper to the input direction) will either be ignored by the router or cause unexpected behavior, leading to QoS failures.

Answer

Using the 'bandwidth percent' command in a class that also has a priority queue.

Answer

Insufficient bandwidth on the subscriber line.

Question 12

Which three BGP attributes are considered before the MED in the BGP best path selection process?

Accepted Answer

Weight. Weight, local preference, and AS_PATH length are considered before MED. ORIGIN is also before MED but AS_PATH is longer.

Answer

Next-hop metric

Answer

Multi-Exit Discriminator (MED)

Question 13

In a BGP confederation, which AS number is used in the AS_PATH to prevent loops within the confederation?

Accepted Answer

Private AS numbers (64512-65535). Confederation uses private AS numbers (from 64512 to 65535) for sub-ASs, and these are prepended to the AS_PATH but not shown to external peers.

Answer

The same AS number as the confederation ID

Answer

Public AS numbers

Answer

No AS number is prepended

Question 14

A service provider is implementing Segment Routing in an IS-IS network. Which TLV is used to advertise the Segment Routing Global Block (SRGB)?

Accepted Answer

TLV 242. The IS-IS Router Capability TLV (242) carries sub-TLVs including the SR Capabilities sub-TLV that advertises the SRGB.

Answer

TLV 22

Answer

TLV 229

Answer

TLV 135

Question 15

In OSPF, which type of area does not allow external routes and only accepts a default route?

Accepted Answer

Stub area. A stub area blocks Type 5 LSAs and injects a default route; it does not accept external routes from other areas.

Answer

Backbone area

Answer

NSSA

Answer

Totally stubby