350-501 MPLS and Segment Routing Practice Test 8 — 15 Questions

Question 1

An engineer is configuring EVPN IRB (Integrated Routing and Bridging) to provide IP connectivity between tenants across a service provider network. Which THREE components are essential for EVPN IRB operation? (Choose three.)

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

Accepted Answer

IP-VRF for each tenant.. EVPN IRB requires an IP-VRF to represent the tenant, a bridge domain (EVI) for Layer 2, and IRB interfaces (Layer 3 gateway) that connect the bridge domain to the VRF. BGP EVPN control plane is also needed.

Answer

LDP or SR for label distribution.

Answer

MPLS-TE tunnels for transport.

Question 2

In MPLS, which label operation is performed by a Penultimate Hop Popping (PHP) router?

Accepted Answer

Pop the top label from the stack. In PHP, the penultimate router pops the label before forwarding to the egress, reducing the egress router's work.

Answer

Swap the top label with a new label

Answer

Push a new label onto the stack

Answer

Swap and push an additional label

Question 3

Which label distribution mode does LDP use by default in Cisco IOS?

Accepted Answer

Downstream unsolicited. LDP uses downstream unsolicited mode by default, where a router advertises labels to all neighbors without being asked.

Answer

Downstream on-demand

Answer

Upstream unsolicited

Answer

Upstream on-demand

Question 4

Which RSVP-TE message is used to reserve resources along the path and includes the Explicit Route Object (ERO)?

Accepted Answer

PATH. The PATH message is sent from the source to the destination to request resource reservation and includes the Explicit Route Object (ERO), which specifies the path to be taken. The RESV message, sent upstream in response, includes objects like LABEL, STYLE, and RECORD_ROUTE, but not the ERO.

Answer

RESV_CONFIRM

Answer

PATH_TEAR

Answer

RESV

Question 5

Which label is used for an Adjacency SID in SR-MPLS?

Accepted Answer

A label from the dynamic label range. The Adjacency SID is local to the router and represents a specific link; it is typically allocated from the dynamic label range, not the SRGB.

Answer

A label from RSVP-TE reserved range

Answer

A label from the static label range

Answer

A label from the SRGB (Segment Routing Global Block)

Question 6

What is the purpose of Constrained Shortest Path First (CSPF) in MPLS-TE?

Accepted Answer

To find a path that satisfies traffic engineering constraints and is as short as possible. CSPF computes paths that meet TE constraints such as bandwidth, affinity, and explicit hops while optimizing the path cost.

Answer

To distribute labels for LDP

Answer

To calculate the best path for L3VPN

Answer

To compute the shortest path without any constraints

Question 7

In SRv6, what is the function of the 'End.DT4' behavior?

Accepted Answer

Decapsulation and IPv4 lookup in a VRF table. End.DT4 is a SRv6 endpoint behavior that decapsulates an IPv6 packet with an SRH and performs a lookup in the IPv4 VRF table for L3VPN.

Answer

Decapsulation and IPv6 lookup in a VRF table

Answer

Decapsulation and Ethernet switching

Answer

Encapsulation and forwarding to an IPv6 destination

Question 8

Which RSVP-TE filter style is commonly used for MPLS-TE tunnels to allow multiple senders on the same session?

Accepted Answer

Shared Explicit (SE). Shared Explicit (SE) allows multiple senders, each with its own filter spec, but they share the same reservation. Fixed Filter (FF) is per sender. The question likely refers to SE style.

Answer

Distinct Explicit (DE)

Answer

Fixed Filter (FF)

Answer

Wildcard Filter (WF)

Question 9

In MPLS-TE Fast Reroute (FRR), what is a 'detour'?

Accepted Answer

A backup LSP that protects a single primary LSP. A detour is a 1:1 protection mechanism where a backup LSP is created for each protected LSP, often pre-signaled.

Answer

A secondary path for load balancing

Answer

A bypass tunnel that protects multiple LSPs

Answer

A mechanism to reroute traffic after failure detection

Question 10

Which EVPN component ensures that only one of the multi-homed PEs forwards traffic to the CE for a given Ethernet segment?

Accepted Answer

DF Election. DF election determines which PE forwards traffic for a given VLAN to avoid duplication.

Answer

Split Horizon

Answer

Aliasing

Answer

ESI (Ethernet Segment Identifier)

Question 11

In SR-MPLS, what is the purpose of the SRGB (Segment Routing Global Block)?

Accepted Answer

To provide a global label space for prefix SIDs. SRGB is a reserved label range used for globally significant prefix SIDs. All routers in the domain use the same SRGB to ensure consistent label mapping.

Answer

To define the range of labels used for LDP

Answer

To reserve labels for MPLS-TE tunnels

Answer

To allocate labels for adjacency SIDs

Question 12

Which SRv6 SID behavior is used to support EVPN-IRB (Integrated Routing and Bridging) for L2VPN with bridging?

Accepted Answer

End.DT2U. End.DT2U is used for L2VPN bridging (EVPN VPWS) and EVPN-IRB uses End.DT2U for bridge domain.

Answer

End.X

Answer

End.DT4

Answer

End.DT6

Question 13

Which two statements about LDP liberal label retention are true? (Choose two.)

Accepted Answer

It allows faster convergence after a topology change.. Liberal label retention is the default mode in Cisco IOS and does not require explicit configuration; it retains all labels even if not used (D) and speeds convergence because labels are already available after a topology change (B). Option C describes conservative retention, and option E is false because liberal retention is default and does not require manual filtering.

Answer

It requires explicit configuration of the label retention mode in Cisco IOS.

Answer

It conserves memory by only storing labels for next-hop neighbors.

Answer

It requires manual configuration of label filtering.

Question 14

Which three are characteristics of SR-TE policies? (Choose three.)

Accepted Answer

They are defined at the headend router with a destination and color.. SR-TE policies are stateful at the headend, use segment lists for path steering, and can be associated with a color for traffic engineering.

Answer

They require RSVP-TE signaling to maintain state.

Answer

They require per-flow state at intermediate routers.

Question 15

Which two are benefits of using EVPN-VPWS over traditional VPWS? (Choose two.)

Accepted Answer

Eliminates the need for pseudowire configuration on each PE.. EVPN-VPWS provides multi-homing with fast convergence and simplifies provisioning using BGP.

Answer

Uses MPLS-TE tunnels for path protection.

Answer

Supports only point-to-point topologies.

Answer

Requires LDP for label distribution.