Cisco 300-515 Practice Test Questions, Exam Dumps

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300-515 Cisco Practice Test Questions and Exam Dumps

Question No 1:

Which utility can you use to validate an LSP in an MPLS environment?

A. uRPF
B. MPLS LSP ping
C. logging
D. RSVP

Correct Answer: B

Explanation:

The utility used to validate a Label Switched Path (LSP) in an MPLS (Multiprotocol Label Switching) environment is MPLS LSP ping. This tool is specifically designed to test the LSPs in MPLS networks by sending ping-like messages along the path, verifying the integrity of the LSPs and ensuring that packets are forwarded as expected. This utility allows network engineers to troubleshoot MPLS paths, check label distribution, and confirm connectivity across the MPLS network.

Option A, uRPF (Unicast Reverse Path Forwarding), is a security feature that ensures traffic is coming from a legitimate source based on routing tables, but it does not validate LSPs in an MPLS environment.

Option C, logging, while important for monitoring network operations, does not specifically validate LSPs. Logging can capture events and issues that might relate to LSPs, but it doesn't directly test or validate the path.

Option D, RSVP (Resource Reservation Protocol), is used to establish and maintain LSPs by signaling and reserving resources for data paths, but it does not validate an existing LSP. RSVP is involved in the creation of LSPs rather than their validation.

Question No 2:

What is the primary function of a VRF on a router?

A. It enables the router to support multiple separate routing tables, which allows the device to handle overlapping IP addresses.
B. It enables a router to run BGP and a distance vector routing protocol at the same time, which allows it to serve as a VPN endpoint between remote sites.
C. It enables a router to configure VLANs locally, which provides segregation between networks.
D. It enables the router to provide faster switching through the network by using labels to identify the input and output interfaces for neighbor routers.

Correct Answer: A

Explanation:

The primary function of Virtual Routing and Forwarding (VRF) on a router is to allow the device to maintain multiple, separate routing tables. This enables the router to support overlapping IP address spaces by isolating network traffic for different virtual networks. Each VRF instance creates a separate virtual routing table, which allows for different sets of routing decisions and paths to exist on the same physical router. This makes VRF essential in environments such as service provider networks where multiple customers might be using the same router and could have overlapping IP address ranges.

By separating these routing tables, VRF provides logical separation between different network segments while still allowing the traffic to flow through the same physical infrastructure. This separation is commonly used in scenarios such as VPNs, where different customer networks are isolated from each other but still share common physical resources.

Option B discusses running multiple routing protocols like BGP and a distance vector routing protocol; however, VRF does not directly address this functionality. While VRF can be used in VPN setups, it does not enable the running of multiple routing protocols at the same time. Instead, it isolates different routing tables to create logical separation.
Option C talks about configuring VLANs locally, which is more related to Layer 2 network segmentation, not the function of VRF, which operates at Layer 3 for routing purposes.
Option D describes MPLS (Multiprotocol Label Switching), where labels are used to identify traffic paths for faster switching across the network. This is different from the functionality of VRF, which does not involve labeling for faster switching.

Therefore, the correct answer is A, as VRF's primary role is to enable multiple, separate routing tables, handling overlapping IP addresses and providing logical network separation.

Question No 3:

Which two statements describe primary differences between MPLS Layer 2 and Layer 3 VPNs? (Choose two.)

A. Layer 2 VPNs use IPsec tunneling, but Layer 3 VPNs use L2TPv3 tunneling.
B. Layer 2 VPNs use AToM, but Layer 3 VPNs use MPLS/BGP.
C. Layer 2 VPNs use BGP, but Layer 3 VPNs use VPLS.
D. Layer 2 VPNs use L2TPv3 tunneling, but Layer 3 VPNs use GRE tunneling.
E. Layer 2 VPNs use IPsec tunneling, but Layer 3 VPNs use pseudowires to provide tunneling.

Correct Answer: B, E

Explanation:

MPLS VPNs are often used to create virtual private networks, but Layer 2 and Layer 3 VPNs differ in terms of their tunneling methods, protocols, and the level of encapsulation used.

Layer 2 VPNs use AToM, but Layer 3 VPNs use MPLS/BGP (Option B):
This is a correct distinction. Layer 2 VPNs (L2VPNs) typically use AToM (Any Transport over MPLS) to transport Layer 2 frames over an MPLS network, which is focused on point-to-point connectivity for Ethernet, ATM, or Frame Relay services. In contrast, Layer 3 VPNs (L3VPNs) use MPLS with BGP (Border Gateway Protocol) to route Layer 3 IP packets between customer sites, enabling IP-based virtual routing across an MPLS backbone. The use of BGP allows for the management of IP routing tables for each customer.
Layer 2 VPNs use IPsec tunneling, but Layer 3 VPNs use pseudowires to provide tunneling (Option E):
This is a valid difference. Layer 2 VPNs often use IPsec for secure tunneling, allowing for Layer 2 traffic to be securely transmitted across a public network. This is especially useful in scenarios where data link layer connectivity needs to be maintained over untrusted networks. On the other hand, Layer 3 VPNs typically use pseudowires, which provide a virtual point-to-point connection across an MPLS network, enabling Layer 3 IP packets to be forwarded transparently, maintaining the routing functionality without the need for secure IPsec tunneling.

The other options are incorrect for the following reasons:

Option A is incorrect because Layer 2 VPNs typically use L2TPv3 or MPLS pseudowires for tunneling, not IPsec. Layer 3 VPNs also do not typically use L2TPv3 but instead rely on BGP for routing.
Option C is incorrect because Layer 2 VPNs do not typically use BGP as a routing protocol for VPN operation. Instead, they use technologies like VPLS (Virtual Private LAN Service) to emulate Layer 2 services. Layer 3 VPNs use BGP to manage IP routing tables across multiple sites.
Option D is incorrect because Layer 2 VPNs typically use L2TPv3 or MPLS pseudowires for tunneling, while Layer 3 VPNs use MPLS and BGP as part of their infrastructure, not GRE tunneling, which is more common for general-purpose network tunnels but not specifically for MPLS Layer 3 VPNs.

In conclusion, the two correct answers are B and E, as they accurately describe the primary differences in tunneling methods and protocols between Layer 2 and Layer 3 MPLS VPNs.

Question No 4:

Refer to the exhibit. A network engineer has been called to configure the four PE devices in order to enable full communication among the four CE devices connected to them. While starting to configure, he experienced a connectivity issue.

Which two tasks should the engineer perform in order to begin the process correctly? (Choose two.)

A. Configure PE3 to export route-targets 100:1 and 200:2.
B. Configure PE3 to import route-targets 100:1 and 200:2.
C. Configure PE4 to import route-targets 101:1 and 202:2.
D. Configure PE2 to export route-targets 300:3 and 400:4.
E. Configure PE1 to import route-targets 300:3 and 400:4.

Answer: B, C

Explanation:

To begin configuring the PE devices for full communication among the CE devices, the engineer must ensure that the import and export of route-targets are properly configured on the PE devices. Route-targets in MPLS VPNs are used to control the distribution of routing information between PEs.

B. Configure PE3 to import route-targets 100:1 and 200:2: This is necessary because PE3 needs to import the correct route-targets for the networks it will exchange with its neighboring devices. These route-targets should correspond to the correct VPNs it will interact with, ensuring that routes are imported properly for communication.
C. Configure PE4 to import route-targets 101:1 and 202:2: Similarly, PE4 needs to import its respective route-targets. This ensures that it can receive routing information relevant to the connected CE devices, enabling communication between the devices on different sides of the network.

Let's review the other options:

A. Configure PE3 to export route-targets 100:1 and 200:2: While exporting route-targets is necessary for distributing routing information to other PEs, this task is not immediately required to address the connectivity issue. Importing the necessary route-targets is the priority.
D. Configure PE2 to export route-targets 300:3 and 400:4: Similar to option A, PE2 must export routes, but this is not as critical as ensuring that the necessary import tasks (like those in options B and C) are completed.
E. Configure PE1 to import route-targets 300:3 and 400:4: PE1’s configuration should also be correct, but the task of importing route-targets on PE1 is secondary compared to ensuring that the initial communication setup is completed between PE3 and PE4.

Thus, B and C are the correct tasks to begin addressing the issue and ensuring full communication.

Question No 5:

Refer to the exhibit. If the two devices are operating normally, which two conclusions can you draw from this configuration? (Choose two.)

A. CE1 must use OSPF to establish a neighbor relationship with PE1.
B. PE1 labels the routes it learns from CE1 with the route-target 222:2 and shares them with its VPNv4 peers.
C. PE1 labels the routes it learns from CE1 with the route-target 111:1 and shares them with its VPNv4 peers.
D. The PE-CE routes between the devices are being exchanged by OSPF.
E. CE1 is supporting CSC.

Answer: C,D

Explanation:

In this scenario, PE1 (Provider Edge) and CE1 (Customer Edge) are likely involved in an MPLS VPN setup, where PE1 connects to VPNv4 peers and CE1 is involved in routing information exchanges.

Option C suggests that PE1 is labeling the routes it learns from CE1 with the route-target 111:1 and sharing them with its VPNv4 peers. This is typical in MPLS VPN configurations where route-targets are used to tag and filter routes as they are shared with other PE devices, which is standard practice in VPN environments to ensure correct route distribution.

Option D indicates that PE-CE routes between the devices are exchanged by OSPF. OSPF is a common IGP (Interior Gateway Protocol) used between PE and CE routers to exchange routing information. The statement likely indicates that OSPF is the protocol used for exchanging routes between PE1 and CE1.

Option A is incorrect because the configuration does not necessarily dictate that OSPF must be used specifically to establish a neighbor relationship between CE1 and PE1. While OSPF is commonly used, other routing protocols like EIGRP or BGP could also be involved.

Option B is incorrect because the route-target 222:2 would typically be used for routes in a different VPN context or for a different VPN instance. The route-target specified in the configuration for PE1 to share routes with its VPNv4 peers is more likely to be 111:1 as stated in C.

Option E is not directly supported by the information in the configuration and is unrelated to the MPLS or VPN context provided. There is no clear indication that CSC (Customer Service Configuration or similar) is being supported by CE1 based on the exhibit details.

Thus, the correct conclusions are C and D.

Question No 6:

Which two frames can be configured on an Ethernet flow point? (Choose two.)

A. of a specific VLAN
B. with different type of service values
C. with identical type of service value
D. with different class of service values
E. with no tags

Correct answers: A, C

Explanation:

Ethernet flow points are used in networking to manage and control traffic flows, particularly in terms of QoS (Quality of Service) and VLAN tagging. The configuration options available for frames at these points allow the network administrator to control how data is prioritized and categorized.

A. of a specific VLAN is correct. An Ethernet flow point can be configured to handle traffic associated with a specific VLAN (Virtual Local Area Network). VLAN tagging helps segregate network traffic, providing logical segmentation within the physical infrastructure. Frames with specific VLAN tags can be managed at the flow point to ensure proper routing, prioritization, and handling of traffic based on VLAN IDs.

B. with different type of service values is incorrect. While the Type of Service (ToS) field can be used for prioritizing traffic, different ToS values in frames would typically require the configuration of traffic policies across the network infrastructure. However, configuring a flow point to manage traffic with different ToS values directly is not standard, as it would be handled more effectively using classification and policy rules rather than frame-specific configuration.

C. with identical type of service value is correct. Configuring frames with identical Type of Service (ToS) values is possible on an Ethernet flow point. The ToS field is used to indicate the priority of packets. In environments where traffic needs to be grouped or managed based on priority, configuring frames to have the same ToS value can ensure that packets are treated uniformly and can be routed, queued, and processed accordingly.

D. with different class of service values is incorrect. The Class of Service (CoS) is a layer 2 (data link layer) concept that is associated with frames, especially in environments using VLANs or other methods of traffic management. While it's possible to use CoS for prioritizing traffic, configuring a flow point with different CoS values for frames would involve more complex traffic management than what is typically configured at the flow point itself. CoS values are often handled separately through policies or network-wide QoS settings.

E. with no tags is incorrect. Frames that are "untagged" (i.e., do not carry VLAN information) are common, but Ethernet flow points are more typically associated with managing traffic based on VLAN or QoS tags. A frame with no tags is treated as a standard Ethernet frame, and while they can certainly exist, flow points are typically configured with more specific traffic management based on tags.

In summary, Ethernet flow points can handle traffic either with a specific VLAN tag or with the same Type of Service value, ensuring proper routing, prioritization, and QoS handling based on network policies.

Question No 7:

In an Ethernet Virtual Circuit environment, which restriction do bridge domains have when STP is running?

A. The STP mode must be RSTP or PVST+
B. Bridge domains must be mapped to a different VLAN.
C. The STP mode must be MSTP
D. Bridge domains must belong to different MST instances.

Correct answer is C

Explanation:

In an Ethernet Virtual Circuit environment, when Spanning Tree Protocol (STP) is running, the STP mode must be MSTP (Multiple Spanning Tree Protocol), which is specifically designed for environments with multiple VLANs and multiple bridge domains. MSTP allows the mapping of multiple VLANs into a single spanning tree instance, thereby improving scalability and network efficiency. This makes C the correct answer.

A is incorrect because RSTP or PVST+ are not the required modes for an Ethernet Virtual Circuit environment; MSTP is the recommended mode for handling multiple bridge domains.
B is incorrect because bridge domains are typically associated with specific VLANs, and while you may map different VLANs to different bridge domains, this is not the primary restriction when STP is running.
D is incorrect because there is no requirement for bridge domains to belong to different MST instances. Multiple bridge domains can exist within the same MST instance, allowing efficient network management.

Thus, the correct answer is C.

Question No 8:

Which type of router can serve as the midpoint router and the tailend router in an MPLS P2MP TE network implementation?

A. headend
B. source
C. transit
D. bud

Answer: D

Explanation:

In a Multiprotocol Label Switching (MPLS) Point-to-Multipoint (P2MP) Traffic Engineering (TE) network, different types of routers play distinct roles in ensuring that traffic is efficiently transmitted from the source to the destinations. In this context, the bud router is specifically designed to serve both as a midpoint router and as a tailend router in the P2MP TE implementation.

Bud router: A bud router serves as the point where traffic from the headend or source router is branched out to multiple destinations. It is called a "bud" because it connects the main traffic flow (from the headend) to multiple outgoing flows to tailend routers. It can function both as the midpoint router (routing traffic within the network) and as the tailend router (the final destination of some traffic streams).

Now, let's analyze the other options:

A. Headend: The headend router is typically the source router in a P2MP TE network. It is responsible for originating the traffic and sending it to the network. The headend router does not serve as a midpoint or tailend router.
B. Source: Similar to the headend, the source router is the originator of the MPLS P2MP traffic. It is the starting point for the distribution of traffic, but it does not serve as a midpoint or tailend router. The role of source is more focused on initiating the traffic flow.
C. Transit: Transit routers are responsible for forwarding traffic through the network but are not the endpoints of the traffic flow. They only pass the traffic along the path between the source and the destination, so they do not act as midpoint or tailend routers.

In conclusion, the bud router is the correct answer because it is the router that can both relay the traffic (midpoint role) and serve as a destination (tailend role) in a P2MP MPLS TE network.

Question No 9:

An engineer is investigating an EVPN traffic flow issue. Which type of traffic should the engineer allow in an EVPN Tree Service in order to fix this issue?

A. known unicast from a leaf to another leaf
B. unknown unicast from a leaf to another leaf
C. multicast from a leaf to another leaf
D. known unicast from a root to another root

Correct answer: B

Explanation:

In an EVPN (Ethernet Virtual Private Network) environment, traffic flows are carefully controlled based on the type of communication involved. The issue mentioned in the question is related to traffic flow between leaves, and it is critical to understand how EVPN handles different types of traffic, such as unicast, multicast, and broadcast.

Known unicast traffic: This refers to packets that are destined for a specific device (i.e., the MAC address is already known). In EVPN, known unicast traffic is generally handled via the control plane (i.e., through the use of MAC address learning and advertisements). However, if the traffic is not explicitly advertised or if there are issues with the underlying EVPN configuration, this traffic may not flow correctly.
Unknown unicast traffic: This is traffic that is sent to a destination for which the source does not know the MAC address. EVPN addresses this type of traffic by using the multicast distribution tree to flood unknown unicast traffic. If this type of traffic is not allowed or if multicast forwarding is not properly configured, there can be issues with EVPN connectivity, as the traffic will not be appropriately flooded across the EVPN network.
Multicast traffic: Multicast is used in EVPN for efficient delivery of traffic to multiple receivers. However, multicast forwarding and handling may not directly resolve issues with unicast traffic, and multicast forwarding may not always be the core issue when troubleshooting traffic flow issues between leaf devices.
Known unicast from a root to another root: This is not typically the primary issue when investigating traffic flow between leaf devices. The root nodes usually manage the distribution of MAC addresses and related information to the leaf nodes, so problems related to root-to-root traffic are less likely to be the root cause in this scenario.

The critical issue here is unknown unicast traffic. When an EVPN network has issues with forwarding unknown unicast traffic, it is often due to problems with multicast distribution trees or the proper allowance of this type of traffic across the network. By ensuring that unknown unicast traffic is allowed to propagate, the engineer can resolve issues related to traffic flow between leaf devices.

Therefore, the correct answer is B.

Question No 10:

An engineer is investigating an MPLS LDP issue. Which command should an engineer use on a Cisco IOS XE device to display the contents of the LFIB?

A. show mpls forwarding-table
B. show mpls ldp neighbors
C. show mpls ldp labels
D. show mpls ldp bindings

Correct answer: A

Explanation:

In an MPLS (Multiprotocol Label Switching) network, the LFIB (Label Forwarding Information Base) is a table used to determine how to forward labeled packets based on the label value. This table contains entries that map incoming labels to outgoing labels and interface information, effectively guiding how traffic should be forwarded through the MPLS network.

A. show mpls forwarding-table: This command displays the contents of the LFIB, which is exactly what the engineer needs when investigating MPLS LDP issues. It shows how MPLS labels are forwarded and mapped across the network, providing insights into the label forwarding paths.
B. show mpls ldp neighbors: This command is used to display information about the LDP (Label Distribution Protocol) neighbors. While it provides details on which LDP peers are established, it does not show the contents of the LFIB.
C. show mpls ldp labels: This command shows the label bindings that have been distributed by LDP. It reveals the labels that have been assigned to different FECs (Forwarding Equivalence Classes), but it does not show the actual LFIB, which is more about the forwarding decision.
D. show mpls ldp bindings: This command displays the label bindings that have been learned via LDP for different FECs, but it does not show the LFIB itself. The LFIB contains the actual forwarding information based on those bindings.

Thus, the correct command to display the LFIB on a Cisco IOS XE device is A (show mpls forwarding-table). This command directly displays the MPLS forwarding information used by the device to make forwarding decisions based on labels.