350-501 Practice Test 2 — 30 Questions

Question 1

Which three BGP attributes are considered in the route selection process before comparing MED? (Choose three.)

Accepted Answer

Weight. The order: weight, local pref, originate (locally originated), AS_PATH length, ORIGIN, MED. So weight, local pref, and AS_PATH length are before MED.

Answer

MED

Answer

Router ID

Question 2

A service provider is implementing 6PE to carry IPv6 traffic over an existing MPLS IPv4 core. Which BGP extension is required on the provider edge (PE) routers to exchange IPv6 prefixes with an IPv4 next-hop?

Accepted Answer

MP-BGP for the IPv6 address family with an IPv4 next-hop encoded in the MP_REACH_NLRI. 6PE uses BGP multiprotocol extensions (MP-BGP) with the IPv6 Address Family Identifier (AFI) and subsequent AFI (SAFI) to carry IPv6 prefixes. The next-hop is encoded as an IPv4 address using the 'next-hop' attribute with an IPv4 address. This is done via MP_REACH_NLRI for IPv6 with an IPv4 next-hop.

Answer

BGP IPv6 unicast address family with IPv6 next-hop

Answer

BGP IPv4 unicast address family with the IPv6 prefix as a label

Answer

BGP VPNv4 address family

Question 3

An SP is implementing BGP FlowSpec to mitigate DDoS. The FlowSpec rule should match traffic with destination port 80 and DSCP value 0. Which FlowSpec component is used to specify the destination port?

Accepted Answer

Type 3: Destination Port. FlowSpec defines traffic matching criteria using components like destination port (type 3), source port (type 2), etc. Destination port is type 3.

Answer

Type 2: Source Port

Answer

Type 4: ICMP Type

Answer

Type 1: Destination Prefix

Question 4

Which MQC component is used to match traffic based on criteria such as DSCP or IP precedence?

Accepted Answer

Class-map. In the Modular QoS CLI (MQC), the class-map component is used to define traffic classes by matching packets based on criteria such as DSCP (Differentiated Services Code Point) or IP precedence values. The class-map uses match statements (e.g., match ip dscp, match ip precedence) to classify traffic, which is then applied within a policy-map for QoS actions. This makes class-map the correct MQC component for traffic matching.

Answer

Service-policy

Answer

Policy-map

Answer

Access-list

Question 5

A service provider uses a centralized automation system to manage QoS policies via NETCONF and YANG. When attempting to push a new policy-map, the device returns an error indicating that the policy-map type is not supported in the specified location. What is the most likely cause?

Accepted Answer

The policy-map is being applied to an interface that does not support hierarchical QoS. The error indicates that the policy-map type is not supported in the specified location. This typically occurs when a policy-map is applied to an interface that does not support hierarchical QoS (HQoS), such as a physical interface that requires a service-policy under a parent policy-map. The NETCONF/YANG operation succeeds in syntax but fails due to device-level capability constraints.

Answer

The YANG module for QoS is not installed on the device

Answer

The NETCONF session is not authenticated

Answer

The automation system is using the wrong namespace

Question 6

Which LDP mode uses downstream unsolicited label distribution and liberal label retention?

Accepted Answer

Downstream unsolicited with liberal retention. Downstream unsolicited (DU) label distribution is the default mode in LDP, where each LSR advertises labels for all its directly connected prefixes to its neighbors without waiting for a request. Liberal label retention means the LSR stores all received label bindings, even if they are not currently used for forwarding, which enables rapid convergence upon topology changes.

Answer

Downstream on demand with liberal retention

Answer

Upstream unsolicited with liberal retention

Answer

Downstream on demand with conservative retention

Question 7

An engineer is configuring MPLS VPN and needs to ensure that customer traffic is automatically marked with a specific QoS policy based on the VPN. Which method should be used to propagate QoS markings across the MPLS network?

Accepted Answer

Use MPLS EXP bits to mark traffic at the ingress PE and map to QoS at egress. In an MPLS VPN environment, QoS markings must be preserved across the MPLS backbone. MPLS EXP (Experimental) bits are the standard mechanism to carry QoS information within the MPLS label stack. At the ingress PE, customer traffic is classified and marked with the appropriate EXP bits based on the VPN or other criteria. The egress PE then uses these EXP bits to map traffic to the correct QoS policy, ensuring end-to-end QoS treatment.

Answer

Use 802.1p CoS on the CE-PE link and preserve it across the MPLS backbone

Answer

Use IP ToS bits to mark traffic and rely on MPLS to preserve them

Answer

Set DSCP at the ingress PE and preserve it across the MPLS backbone

Question 8

A customer is using a Cisco ASR 9000 router with hierarchical QoS (HQoS) on a subscriber interface. The parent policy sets a shape rate of 10 Mbps, but the observed traffic rate is only 8 Mbps. What is a common misconfiguration that would cause this?

Accepted Answer

The child policy includes a police command that is limiting traffic below the parent shaper rate. In hierarchical QoS (HQoS) on a Cisco ASR 9000, the parent policy shapes traffic to a specified rate, but if the child policy includes a police command, that policer can independently drop or mark down traffic before it reaches the parent shaper. This causes the observed traffic rate to be lower than the parent shape rate, as the child policer is the actual bottleneck. The correct answer is A because the police command in the child policy is limiting traffic below the 10 Mbps parent shaper, resulting in only 8 Mbps observed.

Answer

The child policy uses 'bandwidth remaining' instead of 'bandwidth'

Answer

The child policy includes a bandwidth command that exceeds the parent shaper rate

Answer

The parent shaper uses 'shape peak' instead of 'shape average'

Question 9

What is the primary function of the NED (Network Element Driver) in NSO?

Accepted Answer

Abstract the device configuration and map YANG to device CLI. The NED (Network Element Driver) in Cisco NSO is the component that abstracts the native device configuration and translates YANG data models into device-specific CLI commands or protocols (e.g., SNMP, NETCONF). This allows NSO to manage heterogeneous devices using a unified YANG-based service model, making option A correct.

Answer

Provide RESTCONF endpoints

Answer

Store the configuration database

Answer

Handle northbound API requests

Question 10

An engineer is configuring RSVP-TE fast reroute for link protection. Which protection method uses a pre-configured bypass tunnel that protects multiple LSPs on the same link?

Accepted Answer

Facility backup. In RSVP-TE FRR, facility backup uses a bypass tunnel that can protect multiple LSPs on the same link. In contrast, 1:1 detour creates a separate detour LSP for each protected LSP.

Answer

Local Path Protection

Answer

Global Repair

Answer

1:1 detour

Question 11

A provider is implementing EVPN for data center interconnect. They require multi-homing with all-active load balancing and fast convergence using BGP. Which EVPN feature enables this?

Accepted Answer

Ethernet Segment Identifier (ESI). EVPN uses Ethernet Segment Identifier (ESI) for multi-homing. All-active mode allows load balancing across multiple PE nodes, and BGP control plane provides fast convergence via route withdrawal.

Answer

MPLS Traffic Engineering

Answer

BGP Link-State

Answer

VPLS with BGP autodiscovery

Question 12

An SP network uses NSO for service orchestration. Which component in NSO provides the abstraction layer to communicate with different device types using protocols like NETCONF or CLI?

Accepted Answer

NED. NEDs (Network Element Drivers) are plugins that translate NSO's service models to device-specific configurations.

Answer

YANG

Answer

RESTCONF

Answer

CDB

Question 13

Which YANG data modeling construct is used to restrict a leaf value to be a reference to another leaf in the data tree?

Accepted Answer

leafref. The 'leafref' type in YANG is used to restrict the value of a leaf to refer to another leaf in the data tree, enforcing referential integrity.

Answer

when

Answer

must

Answer

choice

Question 14

When DSCP markings are mapped to MPLS EXP bits at the ingress PE router, how many EXP values are available for traffic differentiation in the MPLS core?

Accepted Answer

8. MPLS EXP (now TC) is a 3-bit field, providing 8 possible values (0-7).

Answer

16

Answer

64

Answer

32

Question 15

Which two statements correctly describe the use of DSCP values in the DiffServ model? (Choose two.)

Accepted Answer

DSCP is a 6-bit field allowing 64 distinct values.. DSCP is a 6-bit field with 64 possible values. Per-hop behaviors (PHBs) like EF and AF are defined by DSCP values.

Answer

DSCP values are mapped to MPLS EXP bits at the egress PE.

Answer

DSCP values are used only for voice traffic.

Answer

DSCP value 0 indicates low latency traffic.

Question 16

In SRv6, which endpoint behavior is used for decapsulating the outer IPv6 header and performing an IPv4 lookup (e.g., for L3VPN)?

Accepted Answer

End.DT4. End.DT4 is the SRv6 endpoint behavior that decapsulates the outer IPv6 header and then performs a lookup in the IPv4 VPN table. End.DT6 is for IPv6, and End.DT2U is for L2VPN.

Answer

End.DT6

Answer

End.DT2U

Answer

End.DX4

Question 17

In SR-MPLS, when a router receives a packet with an MPLS label corresponding to an Adjacency SID, what operation does it perform?

Accepted Answer

It pops the label and forwards the packet out of the specific interface.. An Adjacency SID represents a specific link; when a router receives a packet with that label, it pops the label and forwards the packet out of the associated interface, because the Adjacency SID is a 'penultimate hop popping' type of SID.

Answer

It performs a recursive lookup in the FIB to determine the next hop.

Answer

It pushes an additional label and forwards.

Answer

It swaps the label with the next-hop label and forwards.

Question 18

Which TWO are benefits of using EVPN over traditional VPLS for L2VPN services? (Choose two.)

Accepted Answer

Provides MAC address learning via control plane. EVPN offers better control plane (BGP) and supports multi-homing with all-active load balancing.

Answer

Uses LDP for label distribution

Answer

Requires full mesh of pseudowires

Answer

Simpler configuration than VPLS

Question 19

An SP is designing a QoS policy for a customer with voice, video, and data traffic. Which queuing mechanism provides a strict priority queue for voice while ensuring other queues do not starve?

Accepted Answer

LLQ. Low Latency Queuing (LLQ) combines a strict-priority queue for delay-sensitive traffic like voice with CBWFQ for all other classes, ensuring voice gets absolute priority while remaining classes are serviced fairly so they do not starve. It is the Cisco-recommended mechanism for converged voice/video/data QoS designs.

Answer

WFQ

Answer

WRED

Answer

CBWFQ

Question 20

In IOS XR architecture, what is the role of the Secure Domain Router (SDR)?

Accepted Answer

It provides isolation for routing protocols and forwarding tables.. An SDR provides a logical partitioning of router resources, allowing multiple independent virtual routers within a single physical chassis.

Answer

It handles all packet forwarding in hardware.

Answer

It is used for OSPF only.

Answer

It manages the admin plane for all line cards.