350-501 Practice Exam 59 — 20 Questions

Question 1

In BGP, an SP router receives multiple routes to the same prefix. The first route has a weight of 100, LOCAL_PREF of 200, AS_PATH length 3, and is learned via eBGP. The second route has weight 50, LOCAL_PREF 150, AS_PATH length 2, and is learned via iBGP. According to BGP route selection, which route will be preferred?

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

Accepted Answer

The first route (weight 100). BGP selection order: highest weight first. Route 1 has weight 100, Route 2 has weight 50, so Route 1 is preferred regardless of other attributes.

Answer

The second route (AS_PATH length 2)

Answer

The first route (eBGP learned)

Answer

The second route (LOCAL_PREF 150)

Question 2

In OSPF TE extensions for RSVP-TE, which LSA type is used to carry TE information (such as link attributes) in OSPF?

Accepted Answer

Type 10 Opaque LSA. Opaque LSA Type 10 (Area-local) is used for TE information in OSPF. Type 9 is link-local, Type 11 is AS-scoped.

Answer

Type 11 Opaque LSA

Answer

Type 5 AS-external LSA

Answer

Type 9 Opaque LSA

Question 3

An SP customer reports intermittent voice quality issues. The engineer wants to measure jitter and packet loss between two remote sites using Cisco IP SLA. Which IP SLA operation type should be configured?

Accepted Answer

UDP Jitter. The UDP Jitter operation (option E) is correct because it measures both one-way jitter and packet loss by sending UDP packets with precise timestamps, which is essential for diagnosing voice quality issues. Unlike other IP SLA operations, UDP Jitter specifically tracks inter-packet delay variation (jitter) and loss patterns that directly impact VoIP and real-time traffic.

Answer

DNS Query

Answer

ICMP Echo

Answer

HTTP Get

Answer

TCP Connect

Question 4

Which RSVP reservation style is most commonly used in MPLS-TE to allow sharing of resources among multiple LSPs of the same session?

Accepted Answer

Shared Explicit (SE). Shared Explicit (SE) style allows multiple senders to share a reservation, which is typical for MPLS-TE where the headend may have multiple LSPs to the same destination.

Answer

Wildcard Filter (WF)

Answer

Distinct Filter (DF)

Answer

Fixed Filter (FF)

Question 5

Which access technology uses wavelength division multiplexing to provide symmetric gigabit speeds in fiber-optic networks?

Accepted Answer

XGS-PON. XGS-PON uses wavelength division multiplexing to support symmetric 10 Gbps speeds, while GPON is asymmetric and DSL/cable are copper-based.

Answer

Cable

Answer

GPON

Answer

DSL

Question 6

An ISP operates an MPLS Layer 3 VPN backbone. A customer, Corporation X, has four sites (A, B, C, D) each connected to a different PE router (PE-A, PE-B, PE-C, PE-D). They use OSPF as the CE-PE routing protocol. Sites A, B, and C can exchange routes without issue. However, Site D suddenly loses connectivity to Site B, though it can still reach Sites A and C. Show commands on PE-D reveal that the VRF for Corporation X imports RT:100:200, and the route for Site B (prefix 10.10.20.0/24) is present in the BGP VPNv4 table with RT:100:200 and next-hop 10.0.2.2. The OSPF neighbor between PE-D and the CE at Site D is up, and no route filters are configured. ‘ping 10.10.20.0’ from PE-D fails. What is the most likely cause of the issue?

Accepted Answer

The BGP next-hop (10.0.2.2) for Site B's route is not reachable in PE-D's global routing table.. The route is in the VPNv4 table with the correct RT, so import is working. The next-hop is 10.0.2.2. For the VPNv4 route to be installed into the VRF, the next-hop must be reachable in the global routing table of PE-D. If it is not reachable, the route will not be installed, explaining the loss of connectivity to Site B. This can be verified with 'show ip route 10.0.2.2' on PE-D. Option A is incorrect because OSPF route type does not affect BGP redistribution. Option B is incorrect because the route is present in the VPNv4 table with the correct RT, so import is fine. Option C is incorrect because label allocation is working (the prefix is present with labels).

Answer

OSPF route redistribution from PE-B into BGP is set to external type 2, while PE-D expects type 1.

Answer

The route target for Site B is misconfigured on PE-D, not matching the export RT from PE-B.

Answer

PE-D is not assigning an MPLS label for the route to Site B, causing packets to be dropped.

Question 7

A service provider is deploying a QoS policy for a customer with voice, mission-critical data, and best-effort traffic. The voice requires strict priority and low latency. Which queuing mechanism should be used to ensure voice packets are always served before other queues, and what additional measure is necessary to prevent voice traffic from starving other traffic?

Accepted Answer

LLQ for voice; policing on the priority queue to limit voice traffic to a configured rate.. LLQ provides a strict priority queue for delay-sensitive traffic like voice. However, to prevent starvation of other traffic, policing must be applied to the priority queue to limit the amount of voice traffic allowed into it.

Answer

FIFO queuing with a priority list; no policing needed because FIFO handles voice adequately.

Answer

CBWFQ with bandwidth percent for voice; no additional measure needed because CBWFQ inherently prevents starvation.

Answer

WRED for voice; tail drop for data; this ensures low latency for voice.

Question 8

Which MPLS VPN technology allows a service provider to offer overlapping IP addresses to different customers while using a single routing table per VPN?

Accepted Answer

MPLS Layer 3 VPN (BGP/MPLS IP VPN). D is correct because MPLS Layer 3 VPN (BGP/MPLS IP VPN) uses per-VPN routing tables (VRFs) to maintain separate forwarding instances for each customer. This allows overlapping IP addresses across different customers while keeping each VPN's routes isolated. The provider edge routers exchange VPNv4 routes using MP-BGP with route distinguishers (RDs) to make overlapping prefixes unique, and route targets (RTs) control which VRFs import/export those routes.

Answer

Any Transport over MPLS (AToM)

Answer

VPLS

Answer

MPLS Traffic Engineering (TE)

Question 9

Which THREE technologies or protocols are used to implement automated service provisioning in a Cisco service provider network?

Accepted Answer

Cisco NSO. Cisco NSO (Network Services Orchestrator) is a key technology for automated service provisioning because it provides a multi-vendor, service-oriented orchestration layer that uses YANG models and NETCONF to manage device configurations and service lifecycles. It enables operators to define services as templates, then push consistent configurations across the network, drastically reducing manual CLI-based provisioning.

Answer

SNMP

Answer

RIP

Question 10

Which routing protocol is used between CE and PE routers in a typical MPLS L3VPN deployment?

Accepted Answer

BGP. While BGP is a common choice for routing between CE and PE in MPLS L3VPN deployments due to its scalability, policy control, and support for multi-homing, it is not the only protocol. Other dynamic routing protocols such as OSPF, EIGRP, RIP, and static routing are also valid. In a typical deployment, CE and PE can exchange routes using any routing protocol; the PE then redistributes those routes into MP‑BGP for VPN‑v4 advertisement between PEs. The question’s correct answer is BGP because it is the most common and recommended protocol for many scenarios, but candidates should know that the CE‑PE routing protocol is not limited to BGP.

Answer

RIP

Answer

EIGRP

Answer

IS-IS

Question 11

In MPLS forwarding, what label operation does a transit LSR perform on the top label of a labeled packet?

Accepted Answer

Swap. A transit Label Switch Router (LSR) in an MPLS network receives a labeled packet and must forward it toward the egress LSR. The core operation on the top label is a swap: the incoming label is replaced with an outgoing label learned from the downstream LSR via Label Distribution Protocol (LDP) or other label distribution protocols. This maintains the label-switched path (LSP) and ensures the packet continues along the correct path.

Answer

None

Answer

Pop

Answer

Push

Question 12

A network operator deploys a QoS policy on a route reflector to classify traffic based on BGP community values. However, the policy is not matching the intended traffic. Which is the most likely cause?

Accepted Answer

The class-map uses a match statement referencing BGP community values, which are not visible at the QoS classification stage.. BGP community values are exchanged as part of the BGP routing update and are stored in the BGP table, but they are not carried in the IP packet header. QoS classification in Cisco IOS operates on fields within the Layer 2 or Layer 3 packet header (e.g., DSCP, IP precedence, CoS) and cannot inspect BGP attributes like community values. Therefore, a class-map using a match statement for BGP communities will never match traffic at the QoS classification stage, making this the most likely cause of the policy not working.

Answer

The policy-map is applied to the wrong interface.

Answer

The service-policy is applied in the wrong direction (input vs output).

Answer

The class-default class is consuming all traffic.

Question 13

A service provider has a network with multiple PE routers providing MPLS L3VPN services. Customers are complaining that some remote sites are unreachable after a recent software upgrade on PE1. Upon investigation, you notice that PE1 is receiving BGP VPNv4 routes from the route reflector, but some routes are not being installed in the VRF routing table. PE1 is configured with BGP additional-path capability and has a route policy that selects only the best path. The VRF on PE1 has import and export route targets configured correctly. The missing routes have a higher local preference but are not selected due to a tie-break in BGP path selection. Which action should be taken to ensure that all valid routes are installed in the VRF?

Accepted Answer

Configure BGP additional-paths for the VRF and adjust the route policy to allow multiple paths.. B is correct because the issue is that PE1 is configured with BGP additional-path capability but has a route policy that selects only the best path. When BGP path selection ties on local preference and other attributes, additional-path send/receive capability allows multiple paths to be considered, but the route policy must be adjusted to permit multiple paths into the VRF. Without this, only the single best path is installed, even if valid alternative paths exist.

Answer

Reset the BGP session between PE1 and the route reflector.

Answer

Disable route target filtering on PE1 to import all routes.

Answer

Increase the local preference on the route reflector for the missing routes.

Question 14

An SP has configured MPLS TE tunnels for traffic engineering. To verify the status of the TE tunnels, which command provides the most relevant information?

Accepted Answer

show mpls traffic-eng tunnels brief. The 'show mpls traffic-eng tunnels brief' command directly displays the status, state (up/down), and key parameters (e.g., bandwidth, path) of all configured MPLS TE tunnels, making it the most relevant command for verifying TE tunnel status. It provides a concise view of tunnel endpoints, admin/operational states, and signaled bandwidth, which is essential for traffic engineering verification.

Answer

show mpls forwarding-table

Answer

show mpls ldp tunnels

Answer

show ip rsvp reservation

Question 15

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

Accepted Answer

EVI (Ethernet VPN Instance). In EVPN VPWS, two parameters must match between endpoints: the EVI (Ethernet VPN Instance) must match because it defines the EVPN instance and the Route Distinguisher. The Route-target must also match because it ensures that routes are imported/exported correctly between the endpoints. The ESI (Ethernet Segment Identifier) is local to each PE and does not need to match; it identifies the local segment for split-horizon and DF election purposes.

Answer

ESI (Ethernet Segment Identifier)

Answer

VLAN ID of the attachment circuit

Answer

IMET group address

Question 16

A service provider is implementing EVPN for its VPLS replacement. They have configured BGP EVPN on all PEs and have set up an EVPN instance for a customer requiring broadcast, unknown unicast, and multicast (BUM) traffic. The customer reports that broadcast traffic from one site is not being received at another site. The engineer checks the EVPN configuration and finds that the EVI is configured correctly, the route-target matches, and the BGP sessions are established. The engineer also checks the MAC address table on the receiving PE and sees that the source MAC of the broadcast frame is learned on the local interface, but not from the remote VTEP. The engineer suspects an issue with the IMET (Inclusive Multicast Ethernet Tag) route. Which action should the engineer take to verify the IMET route?

Accepted Answer

Check the BGP EVPN route table for IMET (route-type 3) routes using 'show bgp l2vpn evpn route-type 3'.. 'show bgp l2vpn evpn route-type 3' displays the IMET (Inclusive Multicast Ethernet Tag) routes, which are necessary for forwarding BUM traffic between VTEPs. Option A is incorrect because 'show evpn instance detail' shows local EVI configuration but not remote IMET routes. Option C is incorrect because route-type 2 is for MAC/IP advertisement, not IMET. Option D is incorrect because 'show l2vpn vfi' is used for VPLS, not EVPN.

Answer

Use 'show evpn instance detail' to check the EVI configuration.

Answer

Use 'show bgp l2vpn evpn route-type 2' to verify MAC/IP routes.

Answer

Use 'show l2vpn vfi' to verify the VPLS forwarding instance.

Question 17

A service provider operates an MPLS-TE network using RSVP-TE with a full mesh of tunnels between core routers. The network uses OSPF as IGP with traffic engineering extensions. Recently, a new headend router PE-New was added and configured with several TE tunnels to remote destinations. However, some tunnels repeatedly go down after a few minutes and show in the 'down' state with the error 'Tunnel path option 0: no path to destination (TEDB lookup failed)'. The TE tunnels that remain up are those to destinations that are directly connected to the same OSPF area. The network has multiple OSPF areas (area 0, 1, 2) with inter-area routes redistributed. The operator suspects the issue is related to the TEDB (Traffic Engineering Database) not having complete information. Which action is MOST likely to resolve the issue?

Accepted Answer

Change the IGP to IS-IS with wide metrics and enable MPLS-TE on all IS-IS levels. The issue is that OSPF does not flood traffic engineering (TE) information across area boundaries by default. The TEDB on PE-New lacks topology data for inter-area destinations, so tunnel path computation fails. IS-IS, when configured with wide metrics and MPLS-TE enabled on all levels, floods TE link-state information throughout the entire routing domain (both Level-1 and Level-2), ensuring the TEDB is complete. This resolves the problem. Option D (static routes) does not populate the TEDB. Option B does not help because adding loopbacks to OSPF does not provide TE information. Option A (priorities) only affects tunnel setup and preemption, not TEDB completeness.

Answer

Increase the tunnel hold-priority and setup-priority values

Answer

Add the remote loopbacks to OSPF using network statements in area 0

Answer

Configure static routes for the remote destinations on PE-New

Question 18

Based on the exhibit, which label operation will occur when a packet destined to 10.2.2.1 enters PE1 with label 17?

Accepted Answer

Swap label 17 to label 18. The exhibit shows an MPLS VPN scenario where PE1 receives a labeled packet destined for 10.2.2.1. The incoming label 17 corresponds to the VPNv4 route for 10.2.2.1/32, and the LFIB on PE1 indicates a swap operation to label 18, which is the transport label used to forward the packet across the MPLS core toward the next-hop PE.

Answer

Forward with no label (Untagged)

Answer

Pop the label and forward as IP

Answer

Push label 17 onto the packet

Question 19

Match each MPLS VPN technology to its description.

Accepted Answer

MPLS Layer 3 VPN: Uses BGP to distribute customer routes between PE routers. MPLS provides multiple VPN services: Layer 3 VPNs use BGP for route exchange, Layer 2 VPNs emulate L2 circuits, TE controls traffic paths, and Inter-AS extends connectivity across providers. Common confusions involve swapping the L2 and L3 definitions.

Answer

MPLS Layer 3 VPN: Provides transparent transport of Layer 2 frames

Answer

MPLS Layer 2 VPN: Uses BGP to distribute customer routes between PE routers

Question 20

Refer to the exhibit. An engineer configures MPLS LDP on a router. The router has two interfaces with IP addresses 10.0.0.1/30 and 10.0.0.5/30. The engineer notices that LDP sessions are not established. The OSPF neighbor adjacencies are up. What is the most likely cause?

Accepted Answer

LDP is not enabled on the interfaces. D is correct because MPLS LDP requires explicit interface-level activation under the `mpls ip` command. Even if OSPF adjacencies are up and the global LDP process is configured, LDP will not form sessions on interfaces where `mpls ip` is missing. The engineer likely enabled LDP globally but forgot to enable it on the specific interfaces, which is a common oversight.

Answer

The OSPF network statements do not cover the interfaces correctly

Answer

The MPLS MTU is set to 1500, which is too low

Answer

The label range is too small