350-501 Practice Test 49 — 15 Questions

Question 1

An engineer configures an MPLS-TE tunnel with a bandwidth of 100 Mbps and an explicit path that avoids a specific link. Which RSVP message carries the Explicit Route Object (ERO) to signal the path?

Accepted Answer

PATH message. In RSVP-TE, the PATH message includes the ERO to specify the explicit route for the tunnel.

Answer

RESV Confirm message

Answer

PATH Tear message

Answer

RESV message

Question 2

Which THREE are EVPN multi-homing functions? (Choose three.)

Accepted Answer

Ethernet Segment Identifier (ESI) uniquely identifies the multi-homed segment.. EVPN multi-homing uses ESI for identification, DF election to avoid duplicate frames, and aliasing for load balancing.

Answer

Split horizon prevents loops among PEs.

Answer

MAC mobility provides MAC address move detection.

Question 3

In CSPF (Constrained Shortest Path First) for MPLS-TE, which of the following is NOT a typical constraint considered during path computation?

Accepted Answer

Administrative distance. CSPF considers bandwidth, affinity (color), and explicit constraints, but not administrative distance, which is a routing protocol metric.

Answer

Bandwidth

Answer

Affinity (color)

Answer

Explicit path inclusion/exclusion

Question 4

In SRv6, which behavior is used for L3VPN decapsulation (removing the outer IPv6 header and SRH, and forwarding the inner IPv4 packet based on the VPN routing table)?

Accepted Answer

End.DT4. End.DT4 is the SRv6 endpoint behavior for decapsulation and table lookup for IPv4 L3VPN. End.DT6 is for IPv6 L3VPN, End.DT2U is for L2VPN.

Answer

End.DT2U

Answer

End.DT6

Answer

End

Question 5

In an MPLS network using LDP, which LDP mode allocates a label for every prefix in the routing table and advertises it to all LDP neighbors, regardless of whether the neighbor requests it?

Accepted Answer

Downstream unsolicited with liberal label retention. Downstream unsolicited (DU) mode means a router advertises labels for all its prefixes to all neighbors without waiting for a request.

Answer

Downstream on demand with liberal label retention

Answer

Downstream unsolicited with conservative label retention

Answer

Downstream on demand with conservative label retention

Question 6

In an MPLS network using RSVP-TE for traffic engineering, which two mechanisms can be used for fast reroute (FRR) protection? (Choose two.)

Accepted Answer

Facility backup using a bypass tunnel. RSVP-TE FRR offers two protection methods: facility backup (bypass tunnel) and 1:1 protection (detour LSP). Global Repair is not a standard term; Local Protection is used in segment routing.

Answer

Local Protection using segment routing adjacency SID

Answer

Global Repair using a secondary LSP from headend

Answer

Hot Standby Router Protocol (HSRP)

Question 7

Which component in EVPN is used to uniquely identify an Ethernet segment across multiple PE devices in a multi-homing scenario?

Accepted Answer

ESI. The Ethernet Segment Identifier (ESI) is a 10-byte value that identifies a specific multihomed site.

Answer

RT-2

Answer

MAC-VRF

Answer

EVI

Question 8

In SR-MPLS TE, a headend router is configured with an SR Policy that includes an explicit candidate path with segment list [16001, 16003]. What do these numbers represent?

Accepted Answer

MPLS label values representing Node SIDs or Adjacency SIDs. In SR-MPLS, segment lists are composed of MPLS labels. Node SIDs are typically from the SRGB (e.g., 16001 could be a Node SID for a router). Adjacency SIDs would be link-specific labels. The numbers are labels, not interface indices or metric values.

Answer

Interface indices

Answer

Metric values for path calculation

Answer

IPv4 addresses encoded as numbers

Question 9

An SP network engineer needs to implement hierarchical QoS on a PE router to shape customer traffic to a contracted rate of 10 Mbps while providing priority for voice traffic and bandwidth guarantee for critical data. Which MQC configuration correctly achieves this?

Accepted Answer

Create a child policy with class-maps for voice and data; create a parent policy that applies the child policy and shapes to 10 Mbps; apply parent policy to the interface.. Hierarchical QoS (HQoS) is required when you need to shape traffic to a contracted rate (e.g., 10 Mbps) while also applying per-class actions like priority and bandwidth guarantees. Option A correctly uses a child policy to define class-based QoS (priority for voice, bandwidth for critical data) and a parent policy that applies the shape average command to the entire child policy aggregate, enforcing the 10 Mbps contract. This two-level MQC structure ensures that shaping occurs at the parent level before the child policy’s per-class queuing and scheduling are applied.

Answer

Apply a service-policy out with shape and then apply another service-policy in with priority; both on the same interface.

Answer

Apply a single policy-map that includes both shape and priority; no hierarchy needed.

Answer

Use a policy-map with shape average 10 Mbps and then use the bandwidth command for voice and data classes; no hierarchy.

Question 10

A service provider wants to gracefully shut down a BGP session to a customer for maintenance without causing traffic loss. Which BGP feature should be used to signal the peer to reroute traffic before the session is brought down?

Accepted Answer

BGP Graceful Shutdown (GSHUT). BGP Graceful Shutdown (GSHUT) uses a well-known community or attribute to inform peers that the session is going down, allowing them to reroute traffic. BFD detects failures fast but does not signal; TTL propagation is for MPLS; route refresh is for soft reconfiguration.

Answer

BGP TTL Security

Answer

BGP Route Refresh

Answer

BGP Fast External Failover

Question 11

In the DiffServ model, which per-hop behavior (PHB) is associated with the AF31 DSCP value?

Accepted Answer

AF31. DSCP 26 (binary 011010) corresponds to AF31, which is part of the Assured Forwarding class with low drop probability and medium priority.

Answer

CS3

Answer

AF41

Answer

EF

Question 12

A service provider wants to enforce a hard rate limit of 10 Mbps on a subscriber's traffic, dropping any excess packets. Which QoS mechanism should be used?

Accepted Answer

Policing. Policing drops or re-marks traffic exceeding the configured rate, enforcing a hard limit. Shaping buffers excess traffic, which does not enforce a hard drop.

Answer

CBWFQ

Answer

Traffic shaping

Answer

LLQ

Question 13

An SP engineer is using YANG to model a service. Which statement correctly describes the use of a 'leafref' type?

Accepted Answer

It restricts the leaf value to match another leaf's value. Leafref references an existing leaf in the YANG data tree, ensuring consistency.

Answer

It performs data validation using XPath

Answer

It defines a new leaf with a default value

Answer

It allows multiple values to be selected

Question 14

Which TWO statements about MPLS label switching are correct? (Choose two.)

Accepted Answer

The transit LSR performs label swapping.. A transit Label Switch Router (LSR) in an MPLS network performs label swapping: it receives a labeled packet, replaces the incoming label with an outgoing label from its LFIB (Label Forwarding Information Base), and forwards the packet toward the egress LSR. This is the fundamental operation of an LSR in the core of an MPLS domain, as defined in RFC 3031.

Answer

The CE receives a frame with an MPLS label.

Answer

PHP (Penultimate Hop Popping) causes the egress router to pop the label.

Answer

The egress LSR performs label swapping before forwarding.

Question 15

A service provider is preparing for maintenance on a BGP-speaking router. To minimize packet loss, they want to signal to neighbors that the session is being shut down gracefully. Which BGP feature should be used?

Accepted Answer

BGP GSHUT. BGP Graceful Shutdown (GSHUT) uses a well-known community (GRACEFUL_SHUTDOWN) to inform peers to lower the local preference, draining traffic before session termination.

Answer

BGP Route Refresh

Answer

BGP Multipath

Answer

BGP Fast External Failover