350-501 Practice Test 44 — 15 Questions

Question 1

Which technology provides Layer 2 multipoint connectivity over an MPLS network, where customer sites appear to be on the same Ethernet broadcast domain?

Accepted Answer

VPLS. VPLS (Virtual Private LAN Service) emulates a multipoint Ethernet LAN over MPLS. VPWS is point-to-point, EVPN is modern but not always broadcast, and L3VPN is layer 3.

Answer

L3VPN

Answer

VPWS (Virtual Private Wire Service)

Answer

EVPN

Question 2

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 BGP EVPN address-family is not activated.. In EVPN-VPWS, the EVI (EVPN Instance) must be the same on both PEs for the same point-to-point service to ensure proper route matching and label assignment. Therefore, using the same EVI is correct and not a misconfiguration. The most likely issue is that the BGP EVPN address-family is not activated on the PEs. Without this address-family, the PEs cannot exchange EVPN routes (e.g., Type 1 per-EVI AD routes), so the pseudowire cannot be established. The other options—ESI all-zeros (acceptable for single-homed) and MTU mismatch (would cause operational issues but not prevent pseudowire from coming up at the control-plane level)—are less likely to be the root cause.

Answer

The same EVI is used on both PEs.

Answer

The ESI is all-zeros.

Answer

The MTU mismatch on the attachment circuits.

Question 3

Which Cisco router platform is designed for the aggregation layer and supports both mobile backhaul and business services with high density 10GE/100GE interfaces?

Accepted Answer

Cisco NCS. Cisco NCS (Network Convergence System) routers are designed for the aggregation layer, offering high port density and support for various services including mobile backhaul and business connectivity.

Answer

Cisco ASR 9000

Answer

Cisco CRS

Answer

Cisco ISR 4000

Question 4

Which TWO statements accurately describe the differences between GPON and XGS-PON? (Choose two.)

Accepted Answer

XGS-PON uses passive optical splitters.. XGS-PON provides symmetric 10 Gbps, while GPON is asymmetric (2.5G/1.25G). Both use passive optical splitters and WDM.

Answer

GPON offers higher downstream bandwidth than XGS-PON.

Answer

GPON requires active amplification in the field.

Answer

GPON uses WDM while XGS-PON does not.

Question 5

An SP is deploying network slicing for 5G services. They need to ensure ultra-reliable low-latency communication (uRLLC) slice has dedicated bandwidth and low latency. Which mechanism is best suited to guarantee performance for this slice?

Accepted Answer

Flexible Algorithm (Flex-Algo) in IGP. Network slicing using dedicated resources via Flex-Algo or resource reservation can guarantee performance. Flex-Algo allows IGP to compute paths based on constraints like latency, providing dedicated paths for uRLLC.

Answer

Class of Service (CoS) marking on all traffic

Answer

MPLS Traffic Engineering with RSVP-TE

Answer

DiffServ with EF PHB

Question 6

Which TWO statements about IOS XR architecture are correct? (Choose two.)

Accepted Answer

Each routing protocol runs as an independent process in IOS XR.. IOS XR uses distributed OS with process separation, and a commit/rollback model for configuration. It does not have a monolithic kernel; each protocol is a separate process. The admin plane is separate from SDRs.

Answer

Configuration changes in IOS XR take effect immediately without a commit.

Answer

The admin plane in IOS XR is used for customer VPN configuration.

Answer

IOS XR runs a monolithic kernel where all protocols share the same memory space.

Question 7

In a Layer 3 MPLS VPN, a CE router is dual-homed to two different PE routers. The PE routers advertise the same prefix to the route reflector with different route targets. What ensures that only the best path is installed in the VRF?

Accepted Answer

Each PE router independently selects the best path based on BGP attributes.. BGP path selection applies within the VRF. The route with higher local preference or shorter IGP metric to the next-hop determines the best path. Route targets are used for import/export only.

Answer

The route reflector discards duplicate prefixes.

Answer

MPLS labels ensure that only one path is used.

Answer

The CE router must advertise the same route to only one PE.

Question 8

Which access technology uses orthogonal frequency-division multiplexing (OFDM) and is commonly deployed for high-speed internet over copper telephone lines?

Accepted Answer

DSL. VDSL2 and G.fast use OFDM, but DSL generally refers to xDSL technologies. However, the most common high-speed copper access is VDSL2, but the question is broad. The correct answer is DSL as a family.

Answer

GPON

Answer

Cable (DOCSIS)

Answer

Metro Ethernet

Question 9

In the context of EVPN, which BGP address family is used to advertise MAC/VPN routes between PE routers?

Accepted Answer

EVPN (AFI 25, SAFI 70). EVPN uses BGP EVPN address family (AFI 25, SAFI 70) to exchange MAC/VPN routes for L2 and L3 services.

Answer

IPv4 Unicast (AFI 1, SAFI 1)

Answer

L2VPN (AFI 25, SAFI 70)

Answer

VPNv4 Unicast (AFI 1, SAFI 128)

Question 10

Refer to the exhibit. A network engineer is troubleshooting MPLS forwarding for prefix 10.10.10.0/24. The router shows two entries. What does the 'Pop tag' in the outgoing tag indicate?

Accepted Answer

The router will pop the MPLS label before forwarding the packet.. The 'Pop tag' in the outgoing tag indicates that the router is the penultimate hop in the MPLS LSP. According to Penultimate Hop Popping (PHP) behavior, the penultimate router removes (pops) the top label before forwarding the IP packet to the egress LSR, so the egress router receives a pure IP packet and does not need to perform a label lookup. This is standard MPLS behavior defined in RFC 3031.

Answer

The router will swap the label with the local label 16.

Answer

The router has received an error in label distribution.

Answer

The router will forward the packet without an MPLS label.

Question 11

A service provider has deployed QoS on its MPLS backbone to offer different classes of service. The provider notices that EF (Expedited Forwarding) traffic sometimes experiences high jitter during congestion. Following recommended practices, which action is MOST likely to reduce jitter for EF traffic?

Accepted Answer

Use priority queuing (LLQ) for EF traffic with a policer. Priority queuing (LLQ) with a policer ensures EF traffic is served strictly before other queues, reducing jitter, while the policer prevents EF traffic from monopolizing bandwidth. Option B is wrong because traffic shaping smooths bursts but does not provide priority treatment during congestion, so jitter can still occur. Option C is wrong because changing DSCP to AF41 would reclassify EF traffic to a lower priority class, potentially increasing jitter and delay. Option D is wrong because WRED is a congestion avoidance mechanism that drops packets randomly, which can cause jitter for EF traffic; EF should be exempt from WRED.

Answer

Apply traffic shaping on all EF packets at the edge

Answer

Change the DSCP value of EF traffic to AF41 to reduce drops

Answer

Apply weighted random early detection (WRED) on the EF queue

Question 12

In an IS-IS network, a router has a NET of 49.0001.1921.6800.1001.00. What does the '00' at the end represent?

Accepted Answer

SEL (NSAP Selector). The last byte '00' is the SEL (NSAP Selector), which is always '00' for IS-IS routing.

Answer

System ID

Answer

AFI

Answer

Area ID

Question 13

A service provider is deploying LISP (Locator/ID Separation Protocol) to provide mobility and multihoming for customer endpoints. Which LISP component is responsible for maintaining the mapping between Endpoint Identifiers (EIDs) and Routing Locators (RLOCs) and for responding to Map-Request messages from ITRs?

Accepted Answer

Map-Server (MS). The Map-Server (MS) is the central control-plane component in LISP that maintains the authoritative mapping database of EID-to-RLOC entries. When an Ingress Tunnel Router (ITR) sends a Map-Request for an unknown EID, the Map-Server receives it, looks up the mapping, and either responds directly or forwards the request to the appropriate Egress Tunnel Router (ETR) for a reply. This makes the MS the correct answer for maintaining mappings and responding to Map-Requests.

Answer

Ingress Tunnel Router (ITR)

Answer

Map-Resolver (MR)

Answer

Egress Tunnel Router (ETR)

Question 14

Refer to the exhibit. The router is configured as a PE router in an MPLS VPN network. Which option correctly identifies a configuration error that would prevent proper operation?

Accepted Answer

The OSPF network statement uses an incorrect wildcard mask. The OSPF network statement uses a wildcard mask of 0.0.0.0, which matches only the exact IP address 10.1.1.1, but the interface has a /30 prefix (255.255.255.252), so the correct wildcard mask should be 0.0.0.3 to include the entire subnet. This misconfiguration prevents OSPF from advertising the correct network, breaking MPLS VPN CE-to-PE routing.

Answer

The neighbor remote-as should be the same AS number for iBGP

Answer

The interface lacks the 'mpls ip' command

Answer

The BGP network statement does not match the interface prefix

Question 15

What is the purpose of the 'mpls ldp autoconfig' command on an interface?

Accepted Answer

Automatically configure LDP on the interface. The 'mpls ldp autoconfig' command is used on an interface to automatically enable LDP on that interface for all IPv4 address families configured under the OSPF process. This eliminates the need to manually configure 'mpls ldp' on each interface, simplifying deployment in large-scale networks where LDP should be enabled on all OSPF-enabled interfaces.

Answer

Enable MPLS forwarding

Answer

Enable LDP on all interfaces

Answer

Disable LDP on the interface