View Full Cisco CCNP Service Provider 350-501 Exam Dumps and Practice Test Dumps.

 

Question 1

Which protocol is commonly used to distribute VPNv4 routes between PE routers in an MPLS Layer 3 VPN?

1. OSPF
2. BGP
3. LACP
4. STP

Correct Answer: 2

Explanation

BGP is commonly used to exchange VPNv4 and VPNv6 routes between Provider Edge (PE) routers in MPLS Layer 3 VPN environments. MP-BGP extends traditional BGP functionality to carry VPN-specific routing information, including route distinguishers and route targets. This allows multiple customer VPNs to coexist across the same provider infrastructure while keeping their routing information logically separated. OSPF is generally used for internal routing within a network, LACP provides link aggregation, and STP prevents Layer 2 loops. Therefore, BGP is the appropriate protocol for distributing VPN routes between PE routers.

Question 2

Which MPLS label is used to identify a VPN route in an MPLS Layer 3 VPN?

1. VPN label
2. VLAN tag
3. MAC label
4. Ethernet label

Correct Answer: 1

Explanation

In an MPLS Layer 3 VPN, the VPN label identifies the specific VPN route or forwarding context on the provider network. A PE router typically imposes an MPLS label stack when forwarding traffic across the provider network. The outer label can be used for transport across the MPLS core, while the inner VPN label identifies the destination VPN context. VLAN tags and MAC addresses serve different networking functions and are not MPLS VPN labels. Therefore, the VPN label is the correct answer for identifying the VPN forwarding context.

Question 3

Which protocol is primarily used by MPLS routers to distribute labels for IPv4 routes in a traditional MPLS network?

1. BFD
2. RSVP only
3. LDP
4. ARP

Correct Answer: 3

Explanation

Label Distribution Protocol (LDP) is commonly used to distribute MPLS labels associated with routes in traditional MPLS networks. LDP establishes sessions between MPLS-enabled routers and allows them to exchange label bindings. These labels can then be used to forward packets through the MPLS network without performing a full IP lookup at every hop. RSVP-TE can also distribute labels for traffic-engineered paths, but it serves a different purpose. BFD provides fast failure detection, while ARP resolves IPv4 addresses to MAC addresses. Therefore, LDP is correct.

Question 4

What is the primary purpose of a Route Distinguisher (RD) in an MPLS Layer 3 VPN?

1. To encrypt customer traffic
2. To make VPN routes globally unique
3. To calculate the MPLS TTL
4. To select an IGP

Correct Answer: 2

Explanation

A Route Distinguisher makes VPN routes unique when multiple customers use overlapping IPv4 or IPv6 address spaces. The RD is combined with a customer prefix to create a VPN-specific route, such as a VPNv4 route. This allows the provider’s BGP infrastructure to distinguish identical prefixes belonging to different VPNs. An RD does not provide encryption, calculate MPLS TTL values, or select an IGP. Route Targets have a different function: they control the import and export of VPN routes between VRFs. Therefore, making VPN routes globally unique is the correct purpose of an RD.

Question 5

Which BGP extended community controls the import and export of VPN routes between VRFs?

1. Route Target
2. Route Distinguisher
3. Local Preference
4. MED

Correct Answer: 1

Explanation

A Route Target (RT) is a BGP extended community used to control which VPN routes are imported into or exported from a VRF. When a PE exports a customer route, it can attach one or more route-target communities. Other PE routers use their configured import policies to determine which routes should enter a particular VRF. This mechanism allows controlled connectivity between customer sites and VPNs. A Route Distinguisher makes routes unique, while Local Preference and MED are BGP path-selection attributes. Therefore, Route Target is correct.

Question 6

Which technology provides fast failure detection independent of the routing protocol?

1. DHCP
2. BFD
3. FTP
4. NTP

Correct Answer: 2

Explanation

Bidirectional Forwarding Detection (BFD) provides rapid detection of forwarding-path failures between network devices. It operates independently of routing protocols, although routing protocols such as OSPF, IS-IS, and BGP can use BFD information to react more quickly to failures. BFD is particularly useful in service provider networks where fast convergence is important. DHCP provides address configuration, FTP transfers files, and NTP synchronizes time. BFD can significantly reduce the time required to detect certain failures compared with waiting for normal routing protocol timers. Therefore, BFD is the correct answer.

Question 7

Which IGP is commonly used in large service provider networks because of its scalable hierarchical design using areas?

1. RIP
2. OSPF
3. ARP
4. STP

Correct Answer: 2

Explanation

OSPF is a link-state interior gateway protocol that supports hierarchical network design through areas. This allows large networks to be divided into logical sections, reducing the amount of topology information that must be processed throughout the entire network. Service providers may also use IS-IS, which is another scalable link-state IGP. RIP is generally unsuitable for large service provider cores because of its limited metric and slower convergence characteristics. ARP is used for address resolution, while STP is a Layer 2 loop-prevention protocol. Therefore, OSPF is correct.

Question 8

Which protocol is widely used as an IGP in large service provider core networks because of its scalability and flexible hierarchy?

1. IS-IS
2. FTP
3. DHCP
4. TFTP

Correct Answer: 1

Explanation

IS-IS is a link-state interior gateway protocol widely deployed in service provider networks. It supports hierarchical routing through Level 1 and Level 2 areas and can scale effectively in large networks. IS-IS can also support multiple network-layer protocols and has strong integration with traffic-engineering and service-provider technologies. FTP, DHCP, and TFTP are application or network services rather than core IGPs. Although OSPF is also widely used in service provider environments, IS-IS is particularly common in large provider cores. Therefore, IS-IS is the correct answer.

Question 9

Which MPLS forwarding operation removes the top label from a packet before forwarding it?

1. Push
2. Swap
3. Pop
4. Encode

Correct Answer: 3

Explanation

The MPLS pop operation removes the top label from an MPLS label stack. Label operations generally include push, swap, and pop. Push adds a label to the stack, swap replaces the existing top label with another label, and pop removes the top label. Penultimate Hop Popping (PHP) is a common MPLS behavior where the router before the egress PE removes the outer transport label. This can reduce the label-processing work required at the egress router. Therefore, pop is the correct operation for removing the top MPLS label.

Question 10

What does MPLS Traffic Engineering primarily attempt to optimize?

1. Physical cable length
2. Path selection based on network constraints and traffic requirements
3. DNS resolution
4. Ethernet MAC learning

Correct Answer: 2

Explanation

MPLS Traffic Engineering allows service providers to control how traffic traverses the network based on constraints and traffic requirements rather than relying solely on the shortest IGP path. Traffic-engineered paths can help distribute traffic across available links, avoid congested areas, or satisfy bandwidth and policy requirements. Technologies such as RSVP-TE have historically been used for MPLS traffic engineering, while Segment Routing provides another modern approach. DNS resolution and MAC learning are unrelated to MPLS traffic engineering. Therefore, path selection based on network constraints and traffic requirements is correct.

Question 11

Which BGP attribute is commonly used to influence the preferred outbound path within an autonomous system?

1. Local Preference
2. MED
3. Origin
4. Atomic Aggregate

Correct Answer: 1

Explanation

Local Preference is a BGP attribute used within an autonomous system to influence which exit path is preferred for outbound traffic. Higher Local Preference values are generally preferred in Cisco BGP path selection. Because the attribute is propagated throughout the autonomous system, it can help coordinate outbound routing decisions across multiple routers. MED is commonly used to influence inbound path selection from a neighboring autonomous system, while Origin and Atomic Aggregate have different roles. Therefore, Local Preference is the correct answer for influencing the preferred outbound path.

Question 12

Which BGP attribute is commonly used to provide a neighboring autonomous system with a preference for inbound traffic?

1. Weight
2. Local Preference
3. MED
4. Router ID

Correct Answer: 3

Explanation

Multi-Exit Discriminator (MED) can be used to indicate a preferred entry point into an autonomous system when multiple links exist between neighboring autonomous systems. Lower MED values are generally preferred when comparing otherwise applicable paths from the same neighboring AS. MED is therefore commonly used to influence inbound traffic decisions from another AS. Local Preference is primarily used within an AS to influence outbound traffic, while Weight is Cisco-specific and local to a router. Router ID identifies a BGP speaker and is not a traffic-engineering attribute. Therefore, MED is correct.

Question 13

Which BGP feature allows a service provider to maintain separate customer routing tables on the same PE router?

1. VLAN database
2. VRF
3. STP instance
4. EtherChannel

Correct Answer: 2

Explanation

Virtual Routing and Forwarding (VRF) allows a router to maintain multiple independent routing tables. In an MPLS Layer 3 VPN environment, a PE router can use separate VRFs for different customers. This provides logical separation even when different customers use overlapping IP address ranges. Each VRF can have its own interfaces, routes, import/export policies, and forwarding information. VLAN databases and STP instances are primarily Layer 2 mechanisms, while EtherChannel combines physical links. Therefore, VRF is the correct technology for maintaining separate customer routing tables.

Question 14

Which technology is used to provide an MPLS-based Layer 2 VPN service that connects customer Ethernet sites?

1. EVPN
2. DNS
3. DHCP
4. NTP

Correct Answer: 1

Explanation

Ethernet VPN (EVPN) is a technology used to provide Layer 2 and Layer 3 VPN services over provider networks. EVPN uses BGP as its control plane and can provide scalable Ethernet connectivity between customer sites. It is commonly associated with MPLS or Segment Routing transport in service provider architectures. EVPN improves upon traditional Layer 2 VPN approaches by providing a control-plane mechanism for learning and distributing MAC and related reachability information. DNS resolves names, DHCP provides address configuration, and NTP synchronizes clocks. Therefore, EVPN is correct.

Question 15

Which Segment Routing technology uses MPLS labels to identify segments?

1. SR-MPLS
2. SR-DNS
3. SR-ARP
4. SR-FTP

Correct Answer: 1

Explanation

Segment Routing over MPLS, commonly called SR-MPLS, uses MPLS labels to represent segments. A segment represents an instruction or destination within the network, and a sequence of segments can define the desired forwarding path. Segment Routing can reduce dependence on traditional signaling protocols and can integrate with IGPs such as IS-IS or OSPF. SR-MPLS is especially relevant to service provider networks that already operate MPLS infrastructure. The other options are not standard Segment Routing technologies. Therefore, SR-MPLS is the correct answer.

Question 16

What is the primary purpose of Segment Routing Traffic Engineering (SR-TE)?

1. To control traffic paths using a sequence of segments
2. To assign DHCP addresses
3. To replace Ethernet switching
4. To provide DNS resolution

Correct Answer: 1

Explanation

Segment Routing Traffic Engineering (SR-TE) allows network operators to influence traffic paths by specifying a sequence of segments that represents the desired forwarding behavior. A segment can identify a node, adjacency, or other supported instruction. By constructing an appropriate segment list, traffic can be directed through specific network resources or paths. This provides traffic-engineering capabilities without requiring every intermediate router to maintain a separate traffic-engineering tunnel state. DHCP, Ethernet switching, and DNS perform different functions. Therefore, controlling traffic paths using a sequence of segments is correct.

Question 17

Which protocol is commonly used to synchronize clocks across service provider network devices?

1. BGP
2. NTP
3. LDP
4. MPLS

Correct Answer: 2

Explanation

Network Time Protocol (NTP) is commonly used to synchronize clocks between network devices and time servers. Accurate time is important for service providers because logs, monitoring events, troubleshooting records, and security events often depend on consistent timestamps. NTP allows devices to synchronize their clocks with an authoritative time source. BGP exchanges routing information, LDP distributes MPLS labels, and MPLS provides packet forwarding using labels. Although more precise timing technologies such as Precision Time Protocol can be used for specific requirements, NTP is the standard answer for general network clock synchronization.

Question 18

Which protocol can provide a secure encrypted connection for remotely managing a service provider router?

1. Telnet
2. HTTP
3. SSH
4. TFTP

Correct Answer: 3

Explanation

Secure Shell (SSH) provides an encrypted connection for remote management of network devices. It protects authentication credentials and management traffic from being transmitted in clear text. Service provider administrators can use SSH for secure CLI access to routers and other network equipment. Telnet also provides remote terminal access but does not encrypt the session. HTTP is an application-layer protocol and TFTP is a simple file-transfer protocol without built-in encryption. Therefore, SSH is the appropriate choice when secure remote CLI management is required.

Question 19

Which mechanism allows a service provider network to detect a forwarding-path failure quickly and notify a routing protocol?

1. BFD
2. FTP
3. DNS
4. VLAN tagging

Correct Answer: 1

Explanation

Bidirectional Forwarding Detection (BFD) is designed for rapid detection of failures in forwarding paths. BFD sessions exchange control packets between neighboring devices and can detect failures much faster than many traditional routing protocol timers. Routing protocols can integrate with BFD so that a detected failure triggers faster convergence. This capability is particularly valuable in service provider environments where high availability and fast restoration are important. FTP and DNS provide application services, while VLAN tagging identifies Layer 2 traffic. Therefore, BFD is the correct mechanism.

Question 20

Which component of an MPLS Layer 3 VPN architecture connects directly to the customer network?

1. P router
2. PE router
3. Route reflector
4. Route server

Correct Answer: 2

Explanation

The Provider Edge (PE) router connects directly to customer-facing interfaces in an MPLS Layer 3 VPN architecture. The PE maintains customer VRFs and exchanges VPN routes with other PE routers, commonly using MP-BGP. Provider (P) routers generally operate within the service provider core and do not maintain customer VPN routing information. Route reflectors can assist with BGP scalability, while a route server has different control-plane roles depending on the architecture. Therefore, the PE router is the component that directly connects the provider network to the customer network.