350-501 Practice Test 35 — 15 Questions

Question 1

Which TWO are benefits of model-driven telemetry over SNMP polling?

Accepted Answer

Supports structured data models (YANG). Model-driven telemetry uses structured data models defined in YANG, which provides a standardized, hierarchical representation of device state and configuration. This contrasts with SNMP polling, which relies on flat MIB variables and often requires complex parsing of unstructured data. YANG models enable consistent data retrieval across multivendor environments and simplify automation workflows.

Answer

Requires fewer credentials for access

Answer

Works with legacy devices without modification

Answer

Uses XML exclusively

Question 2

In 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?

Accepted Answer

The 3 most significant bits of DSCP are copied to EXP. A common mapping is to copy the three most significant bits of DSCP to EXP, which maps DSCP PHBs into corresponding EXP values.

Answer

EXP is set by the egress PE router

Answer

EXP is set to the same binary as the entire DSCP byte

Answer

EXP is set to a static value per customer

Question 3

A service provider wants to stream interface counters from a Cisco router to a collector using model-driven telemetry. The collector is behind NAT and cannot be reached from the router. Which telemetry model should be used?

Accepted Answer

Dial-out. Dial-out telemetry is the correct model because it allows the router to initiate a TCP connection to the collector, even when the collector is behind NAT and cannot be reached from the router. In dial-out mode, the router acts as the client and pushes telemetry data to the collector's configured IP address and port, bypassing the need for the collector to initiate the connection. This contrasts with dial-in models where the collector must reach the router, which is impossible when the collector is behind NAT.

Answer

SNMP traps

Answer

gNMI

Answer

NETCONF

Answer

Dial-in

Question 4

A service provider is designing a BGP-based network. Which TWO are characteristics of BGP within a service provider core?

Accepted Answer

IBGP sessions require a full mesh or route reflectors to avoid routing loops. IBGP requires either a full mesh of sessions or route reflectors to prevent routing loops. The BGP split-horizon rule states that routes learned from an iBGP peer are not advertised to another iBGP peer, so without a full mesh or route reflectors, reachability information cannot propagate within the AS. Route reflectors break this rule by allowing selected iBGP speakers to re-advertise routes, but they must be deployed with proper cluster and originator ID attributes to avoid loops.

Answer

BGP MED attribute is mandatory for all routes

Answer

BGP uses the AS path for loop prevention in iBGP

Answer

BGP route reflectors always modify the AS path

Question 5

Which THREE BGP path attributes are considered during the best path selection process after local preference? (Choose three.)

Accepted Answer

Multi-exit discriminator (MED). After local preference, the BGP best path selection process evaluates the AS path length. A shorter AS path is preferred because it indicates a less complex path to the destination network. This attribute is directly compared next, making option C correct.

Answer

Next-hop IP address

Answer

Router ID

Question 6

Which THREE components are required for model-driven telemetry with gRPC? (Choose three.)

Accepted Answer

YANG data model. YANG data models (C) are required because they define the structure and semantics of the telemetry data being streamed. gRPC uses YANG as its schema language to encode data in Protocol Buffers (protobuf) or JSON format, ensuring the receiver can parse and interpret the telemetry information correctly.

Answer

SNMP trap receiver

Answer

NETCONF session

Question 7

A service provider uses RESTCONF to automate interface configuration. They need to add a new IPv4 address to an existing interface. Which HTTP method and URI should be used?

Accepted Answer

PATCH /restconf/data/ietf-interfaces:interfaces/interface=GigabitEthernet0/1/ietf-ip:ipv4/address. PATCH is the appropriate HTTP method for a partial update to an existing resource, and the URI targets the IPv4 address list under the specific interface. This allows adding a new IPv4 address without replacing the entire interface configuration, which aligns with RESTCONF's support for partial resource modification as defined in RFC 8040.

Answer

DELETE /restconf/data/ietf-interfaces:interfaces/interface=GigabitEthernet0/1

Answer

POST /restconf/data/ietf-interfaces:interfaces/interface=GigabitEthernet0/1/ietf-ip:ipv4

Answer

PUT /restconf/data/ietf-interfaces:interfaces/interface=GigabitEthernet0/1/ietf-ip:ipv4/address

Question 8

A large service provider is migrating its L2VPN services (VPWS and VPLS) to EVPN-based solutions to improve scalability and support multi-homing. During the rollout for a customer using VLAN-based EVPN for a data center interconnect, the operations team notices frequent MAC address flapping and broadcast storms on one of the attachment circuits connected to a PE router. The PE is configured for EVPN-MPLS with ESI multihoming using all-active mode. The customer has two PEs (PE1 and PE2) connected to the same CE via two separate Ethernet links. The MAC table on PE1 shows the same MAC address alternating between the local AC interface and the remote EVPN peers. What is the most likely cause and the correct action to resolve this issue?

Accepted Answer

Implement ESI multihoming with per-flow load balancing to ensure consistent designated forwarder election.. In all-active multihoming, both PEs forward traffic for the same VLAN, but split-horizon prevents loops. However, if the designated forwarder (DF) election is inconsistent—for example, due to misconfiguration of ESI or DF algorithm—both PEs may forward broadcast/multicast traffic, causing MAC flapping and broadcast storms. Per-flow load balancing ensures consistent DF election by hashing based on flow characteristics, reducing the chance of both PEs forwarding the same MAC addresses. Option B (disabling split-horizon) would worsen loops. Option C (selective multicast) is for optimizing multicast, not for MAC flapping. Option D (MPLS vs VXLAN) does not affect MAC learning loops.

Answer

Disable split-horizon on the local AC interface to allow MAC learning from the CE directly.

Answer

Enable selective multicast on the EVPN instance to reduce broadcast traffic.

Answer

Use MPLS encapsulation instead of VXLAN to avoid MAC address issues.

Question 9

An engineer is configuring an MPLS L3VPN and needs to ensure that the PE router installs VPNv4 routes from a remote PE into the VRF of a customer. The remote PE sends a VPNv4 route with route-target 100:1. Which configuration on the local PE causes the route to be imported into the VRF?

Accepted Answer

vrf definition CUSTOMER
 rd 100:1
 route-target import 100:1. The `route-target import 100:1` command under the VRF definition configures the local PE to accept VPNv4 routes that carry the specified route-target (100:1) from the remote PE. This import RT must match the export RT of the remote PE for the route to be installed into the VRF's routing table. The `rd 100:1` defines the route distinguisher, which is separate from the RT and ensures uniqueness of the VPNv4 prefix.

Answer

router bgp 100
 address-family ipv4 vrf CUSTOMER
 route-target import 100:1

Answer

vrf definition CUSTOMER
 rd 100:1
 route-target both 100:1 route-map IMPORT

Answer

vrf definition CUSTOMER
 rd 100:1
 route-target export 100:1

Question 10

A network engineer is troubleshooting slow BGP convergence after a link failure in an MPLS core. Which feature can be enabled on the PE routers to fast-failover traffic upon BGP next-hop unreachability?

Accepted Answer

BGP Prefix Independent Convergence (PIC). BGP Prefix Independent Convergence (PIC) enables fast failover by pre-installing backup paths into the forwarding table, so when a BGP next-hop becomes unreachable, traffic is immediately switched to the backup path without waiting for BGP reconvergence. This is critical in MPLS cores where slow BGP convergence after a link failure can cause prolonged traffic loss.

Answer

Route Reflector clustering

Answer

Bidirectional Forwarding Detection (BFD)

Answer

Local Preference manipulation

Question 11

Which three components are part of NSO (Network Services Orchestrator) architecture? (Choose three.)

Accepted Answer

YANG models for service definitions. YANG models are the foundation for service definitions in NSO because they define the data structures and constraints for network services using a standardized modeling language (RFC 6020/7950). NSO uses YANG to model both the service layer (customer-facing services) and the device layer (native device configurations), enabling service abstraction and multi-vendor orchestration.

Answer

RADIUS server

Answer

PCEP (Path Computation Element Protocol)

Question 12

An SP engineer is hardening management plane access on IOS XR routers. They want to enforce role-based access control using task groups. Which AAA protocol is required to support attribute-based authorization on IOS XR?

Accepted Answer

TACACS+. TACACS+ supports per-command authorization and attribute-value pairs for role-based access, while RADIUS has limited authorization capabilities. IOS XR uses TACACS+ for task group-based authorization.

Answer

Kerberos

Answer

RADIUS

Answer

LDAP

Question 13

Refer to the exhibit. An engineer has configured an SR-TE policy. What is required for this policy to be used for traffic steering?

Accepted Answer

BGP with color extended community. An SR-TE policy uses a color extended community to identify the policy's color and its associated endpoint. BGP distributes these color extended communities, enabling headend routers to match traffic to the correct SR-TE policy for steering. Without BGP carrying the color extended community, the policy cannot be dynamically selected for traffic engineering.

Answer

Static routing

Answer

IGP with segment routing

Answer

OSPF with opaque LSA

Question 14

Which encapsulation technology is commonly used in service provider networks to separate subscriber traffic in an Ethernet aggregation network?

Accepted Answer

Q-in-Q (802.1ad). Q-in-Q (802.1ad) is the correct encapsulation technology because it allows service providers to stack an outer service VLAN tag (S-Tag) on top of a customer's inner VLAN tag (C-Tag), effectively separating subscriber traffic in an Ethernet aggregation network. This double-tagging mechanism preserves the customer's VLAN space while enabling the provider to aggregate multiple subscribers over a single physical port, which is essential for Metro Ethernet and DSLAM aggregation scenarios.

Answer

VXLAN

Answer

802.1Q

Answer

MPLS

Question 15

Refer to the exhibit. An engineer applies two service policies to the same subinterface in the outbound direction. Which statement describes the expected behavior?

Accepted Answer

Only the SHAKE-1M policy is applied; the CHILD-QOS policy is ignored.. When two service policies are applied to the same subinterface in the same direction, the router only honors the first policy applied; the second policy is ignored. In this case, SHAKE-1M was applied first, so CHILD-QOS is not processed. Cisco IOS does not allow multiple service policies in the same direction on a single interface or subinterface, as each direction can have only one active policy-map.

Answer

The router automatically nests CHILD-QOS inside SHAKE-1M creating hierarchical QoS.

Answer

The router compiles a combined policy that merges classifications.

Answer

Both policies are applied sequentially; traffic is shaped then classified.