350-501 Practice Test 20 — 15 Questions

Question 1

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. For an SR-TE policy to be used, traffic must be steered via BGP with a color extended community matching the policy's color. Without a match, the policy is not activated. Option B: IGP with SR is already configured; Option C: static routing is not relevant; Option D: OSPF opaque LSA is for OSPF extensions, not SR-TE policy activation.

Answer

Static routing

Answer

IGP with segment routing

Answer

OSPF with opaque LSA

Question 2

When configuring EVPN VPWS, which TWO parameters must match between the two endpoints of the pseudowire?

Accepted Answer

EVI (Ethernet VPN Instance). Options A and B are correct. EVI and ESI must match to form a pseudowire. Option C (IMET) is used for multicast but not for VPWS. Option D is not required to match; VLAN IDs can differ. Option E (route-target) is used for route import/export but not mandatory for VPWS endpoint matching.

Answer

Route-target

Answer

VLAN ID of the attachment circuit

Answer

IMET group address

Question 3

A service provider is deploying EVPN-VPWS for point-to-point services. They have set up an EVPN instance with Ethernet Segment Identifier (ESI) and EVI. After configuration, the pseudowire is not coming up. Which misconfiguration is most likely?

Accepted Answer

The same EVI is used on both PEs.. Option B is correct because for EVPN-VPWS, the same EVI must be used on both PEs to establish the pseudowire. Option A is wrong because a non-zero ESI is required, but all-zeros is invalid. Option C is wrong because BGP EVPN address-family is needed but its absence would affect all EVPN services, not just VPWS. Option D is wrong because MTU mismatch causes issues but is less likely than EVI mismatch.

Answer

The ESI is all-zeros.

Answer

The MTU mismatch on the attachment circuits.

Answer

The BGP EVPN address-family is not activated.

Question 4

In an IS-IS segment routing network, after the global 'segment-routing mpls' configuration, which IS-IS configuration is mandatory for label allocation?

Accepted Answer

segment-routing mpls under router isis. Option C is correct because the 'segment-routing mpls' command must be enabled under the IS-IS router configuration to activate label allocation for segment routing. Option A is wrong because 'mpls label protocol sr' is not an IS-IS command; it is a global command. Option B is wrong because IS type does not affect segment routing directly. Option D is wrong because prefix-SID under the interface is for specific prefix assignments, not for enabling label allocation globally.

Answer

mpls label protocol sr

Answer

prefix-sid under the loopback interface

Answer

is-type level-1-2

Question 5

In a Carrier Supporting Carrier (CSC) architecture, which condition is necessary for the customer carrier's BGP routes to be carried over the provider carrier's MPLS backbone?

Accepted Answer

The BGP next-hop on the customer carrier's routes must be reachable via IGP in the provider carrier.. Option D is correct because in CSC, the customer carrier's BGP next-hop must be reachable via the provider carrier's IGP for label switching to work. Option A is wrong because AS numbers can be different; the provider carrier treats the customer carrier as a VPN. Option B is wrong because LDP is used for label distribution in the customer carrier's network, but it's not a condition for the provider carrier. Option C is wrong because the route-target is used for VPN route import/export, but CSC does not necessarily require a VRF on the provider carrier if using BGP-free core.

Answer

The provider carrier's VRF must have the route-target matching the customer carrier's.

Answer

The provider carrier must be in the same AS as the customer carrier.

Answer

The customer carrier must use LDP for label distribution.

Question 6

In an SR network, which configuration is required to activate TI-LFA for link protection?

Accepted Answer

fast-reroute per-prefix ti-lfa under the IGP process. Option C is correct because the command 'fast-reroute per-prefix ti-lfa' under the IGP process (IS-IS or OSPF) explicitly enables TI-LFA. Option A is wrong because 'mpls traffic-eng auto-tunnel primary' is for TE auto-tunnel, not TI-LFA. Option B is wrong because 'label-preferred' is not a valid command. Option D is wrong because 'metric delay' is for IGP convergence, not TI-LFA.

Answer

metric delay interface configuration

Answer

label-preferred under the interface

Answer

mpls traffic-eng auto-tunnel primary

Question 7

An SP is migrating its core network to Segment Routing (SR-MPLS). The network uses IS-IS as the IGP with SR extensions. Which three statements about SR-MPLS architecture are correct?

Accepted Answer

Adjacency SIDs are local to a router and indicate a specific link.. Segment IDs (SIDs) are allocated from the SRGB and advertised via IS-IS; a prefix SID is a global label identifying a specific prefix; adjacency SIDs are local to a router. The SRGB does not have to be identical across all routers, and OSPF also supports SR.

Answer

The OSPF protocol cannot be used for SR-MPLS because it does not support SR extensions.

Answer

The SRGB must be identical across all routers in the domain to ensure global uniqueness.

Question 8

An SP is managing a large MPLS network and needs to verify the MPLS forwarding entries for a specific VRF. Which command provides the most complete information for the VRF?

Accepted Answer

show mpls forwarding-table vrf . Option D is correct because 'show mpls forwarding-table vrf ' displays the label forwarding table for the VRF, including inbound and outbound labels. Option A is wrong because 'show ip cef vrf' shows CEF table, not MPLS labels. Option B is wrong because 'show bgp vpnv4 unicast all labels' shows BGP label bindings, not the forwarding table. Option C is wrong because 'show mpls vrf' is not a valid command.

Answer

show ip cef vrf <name>

Answer

show mpls vrf <name>

Answer

show bgp vpnv4 unicast all labels

Question 9

Which TWO are benefits of using Segment Routing over LDP in a service provider core?

Accepted Answer

Label allocation is per-prefix, not per-interface.. Options A and C are correct. SR supports TI-LFA for fast reroute, and native per-prefix label allocation. Option B is wrong because SR still requires IGP convergence for label distribution. Option D is wrong because SR can be used with TE, but LDP also supports TE. Option E is wrong because SR may actually increase the number of labels due to SID stack.

Answer

Reduces the number of labels in the control plane.

Answer

Eliminates the need for IGP convergence for label distribution.

Answer

Simplifies MPLS TE tunnel configuration.

Question 10

A service provider is designing an MPLS L3VPN network to provide Layer 3 VPN services to multiple customers. Which two statements correctly describe the roles of the Provider Edge (PE) and Customer Edge (CE) routers in this architecture?

Accepted Answer

PE routers advertise customer routes via MP-BGP with route distinguishers and route targets.. PE routers maintain separate VRF tables for each customer VPN and advertise customer routes via MP-BGP with route distinguishers and route targets. CE routers do not participate in the service provider's IGP.

Answer

P routers store all customer VPN routes in their global routing table.

Answer

CE routers perform MPLS label switching between PE routers.

Answer

CE routers participate in the service provider's IGP to exchange loopback addresses.

Question 11

A service provider is migrating its MPLS core from LDP to Segment Routing with MPLS data plane (SR-MPLS). The network currently uses TE tunnels with RSVP-TE for traffic engineering. Which technology can the provider use to continue performing traffic engineering after the migration without requiring RSVP-TE?

Accepted Answer

SR-TE. Option C is correct because Segment Routing offers traffic engineering capabilities via a centralized controller (e.g., PCE) or distributed policies using SR-TE policies, eliminating the need for RSVP-TE. Option A is wrong because LDP does not support traffic engineering. Option B is wrong because BGP-LU only provides LSP labels, not TE. Option D is wrong because MPLS-TE is synonymous with RSVP-TE.

Answer

LDP

Answer

MPLS-TE (RSVP-TE)

Answer

BGP-LU

Question 12

Which THREE of the following are correct statements about EVPN-VXLAN in a data center fabric? (Select three.)

Accepted Answer

EVPN route type 3 is used for BUM traffic forwarding.. Options A, B, and D are correct. EVPN-VXLAN uses BGP EVPN route type 2 for MAC/IP advertisement, route type 3 for inclusive multicast, and VXLAN encapsulation uses a UDP header. Option C is wrong: VXLAN uses multicast or BGP EVPN but not necessarily ingress replication for BUM traffic; it can use multicast or ARP suppression. Option E is wrong: VXLAN is a Layer 2 overlay over a Layer 3 underlay.

Answer

VXLAN is a Layer 3 overlay that requires an IGP in the overlay.

Answer

VXLAN always requires IP multicast in the underlay for BUM traffic.

Question 13

A service provider is deploying EVPN-VPWS to replace legacy pseudowire connections for point-to-point Layer 2 services. They notice that MAC addresses learned from a CE device are not properly advertised to the remote PE. Which EVPN route type is responsible for advertising MAC address reachability information in a VPWS scenario?

Accepted Answer

Route Type 1 (Ethernet Auto-Discovery). Option A is correct because Route Type 1 (Ethernet Auto-Discovery) is used for VPWS per-EVI and per-ES AD routes, which include MAC mobility information. Route Type 2 is for MAC/IP advertisement, but in VPWS, MAC learning is not required typically; however, Route Type 1 carries the MAC address for split-horizon filtering. Option B (RT-2) is for MAC/IP but not the primary for VPWS. Option C (RT-3) is for inclusive multicast. Option D (RT-5) is for IP prefix.

Answer

Route Type 2 (MAC/IP Advertisement)

Answer

Route Type 5 (IP Prefix)

Answer

Route Type 3 (Inclusive Multicast)

Question 14

A network engineer is configuring QoS on a Cisco ASR 9000 router to support multiple traffic classes. The policy must ensure that real-time traffic (EF) is not starved by high-volume bulk data (AF11). Which queuing strategy should be applied to the EF class to provide low latency and strict priority?

Accepted Answer

Priority Queuing (LLQ). Option B is correct because Priority queuing provides a strict priority queue that services the EF class before other queues, ensuring low latency. LLQ is the implementation of priority queuing with CBWFQ. Option A (CBWFQ) provides fair bandwidth allocation but no strict priority. Option C (WRR) is byte-based and not strict. Option D (FIFO) does not differentiate.

Answer

Weighted Round Robin (WRR)

Answer

Class-Based Weighted Fair Queuing (CBWFQ)

Answer

First-In-First-Out (FIFO)

Question 15

A service provider is implementing Multicast VPN (MVPN) in an MPLS backbone. They use Rosen GRE (draft-rosen) for multicast transport. What is the primary limitation of Rosen GRE compared to mLDP-based MVPN?

Accepted Answer

All multicast traffic is sent to every PE in the VPN, even if no receiver exists.. Option C is correct because Rosen GRE uses a default MDT group that carries all multicast traffic, leading to unnecessary traffic replication to PEs that do not have interested receivers. mLDP builds P2MP LSPs precisely where needed. Option A is wrong because both support PIM. Option B is wrong because both require full-mesh of tunnels (Rosen GRE uses GRE, mLDP uses MPLS LSP). Option D is wrong because both can handle SSM.

Answer

It requires full-mesh of GRE tunnels between all PEs.

Answer

It cannot use Source-Specific Multicast (SSM).

Answer

It does not support Protocol Independent Multicast (PIM).

350-501 Practice Test 20 — 15 Questions

Exhibit

350-501 Practice Test 20 — 15 Questions

Exhibit