350-501 MPLS and Segment Routing Practice Test 10 — 15 Questions

Question 1

In MPLS, which operation occurs when a router receives a labeled packet and replaces the top label with a new label before forwarding?

Accepted Answer

Swap. In MPLS, the swap operation replaces the incoming top label with a new outgoing label as per the LFIB entry.

Answer

Lookup

Answer

Pop

Answer

Push

Question 2

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 3

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 4

Which SR-MPLS SID is advertised by an IS-IS router to identify a specific link and is distributed only to adjacent neighbors?

Accepted Answer

Adjacency SID. An Adjacency SID is a local label for a specific adjacency, distributed only to neighbors.

Answer

Prefix SID

Answer

Node SID

Answer

Anycast SID

Question 5

In SRv6, which SID behavior is used to achieve L3VPN IPv6 VPN forwarding, where the SID points to a VPN instance and performs decapsulation and IPv6 lookup?

Accepted Answer

End.DT6. End.DT6 is the SRv6 endpoint behavior for L3VPN over IPv6, performing decapsulation and lookup in the appropriate VPN routing table.

Answer

End.X

Answer

End.DT2U

Answer

End.DT4

Question 6

Which component of an MPLS-TE FRR (Fast Reroute) configuration provides protection for the next-hop node by bypassing it?

Accepted Answer

Node protection. Node protection uses a bypass tunnel that bypasses the protected node, while link protection only bypasses the link.

Answer

Path protection

Answer

Link protection

Answer

Bandwidth protection

Question 7

An engineer wants to configure SR-TE without using RSVP. Which mechanism does SR-TE use to specify the explicit path?

Accepted Answer

Segment list in SR Policy. SR-TE uses a segment list consisting of Node SIDs and/or Adjacency SIDs to define the explicit path, avoiding RSVP state.

Answer

ERO in RSVP PATH message

Answer

Label stack with PHP

Answer

IGP shortest path only

Question 8

In EVPN-VPWS, which identifier is used to uniquely identify an Ethernet Segment for multi-homing?

Accepted Answer

ESI. The Ethernet Segment Identifier (ESI) uniquely identifies an Ethernet segment that is multi-homed to two or more PEs.

Answer

Route Distinguisher

Answer

EVI

Answer

MAC address

Question 9

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 10

Which MPLS label operation is performed by the penultimate hop router in PHP (Penultimate Hop Popping)?

Accepted Answer

Pop. In PHP, the penultimate hop router pops the label before forwarding the packet to the egress router, reducing the egress's workload.

Answer

No operation

Answer

Swap

Answer

Push

Question 11

An SRv6 SID is composed of three parts: Locator, Function, and Arguments. Which part identifies the SRv6-capable node in the network?

Accepted Answer

Locator. The Locator portion of an SRv6 SID identifies the node and is routable in the IGP.

Answer

Argument

Answer

Function

Answer

SRH

Question 12

In EVPN with Integrated Routing and Bridging (IRB), which type of interface is used to connect the bridge domain to the IP-VRF for inter-subnet forwarding?

Accepted Answer

IRB interface. IRB uses an Integrated Routing and Bridging interface (IRB interface) or BVI (Bridge Virtual Interface) to route between VLANs within the EVPN.

Answer

BD interface

Answer

L3VPN interface

Answer

SVI

Question 13

Which TWO statements correctly describe RSVP-TE reservation styles? (Choose two.)

Accepted Answer

Shared Explicit (SE) allows multiple senders to share a reservation but with explicit filters.. Shared Explicit (SE) allows sharing among senders with different selectors, and Fixed Filter (FF) creates distinct reservations per sender.

Answer

Shared Explicit (SE) does not allow any sharing.

Answer

Fixed Filter (FF) is the only style used in MPLS-TE.

Answer

Wildcard Filter (WF) is commonly used in MPLS-TE.

Question 14

Which TWO are characteristics of SR-MPLS when compared to LDP-based MPLS? (Choose two.)

Accepted Answer

Labels are distributed via IGP extensions.. SR-MPLS eliminates LDP and RSVP state, using IGP for label distribution (e.g., via IS-IS TLVs).

Answer

SR-MPLS uses IPv6 SIDs only.

Answer

Labels are distributed using LDP.

Answer

SR-MPLS requires RSVP-TE for traffic engineering.

Question 15

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.