Cisco 350-501 Implementing and Operating Cisco Service Provider Network Core Technologies (350-501 SPCOR) Exam Practice Test

the configuration should ensure that VRF ABC and XYZ have route targets that allow them to import routes from VRF CENTRAL, but not from each other. This can be achieved by careful manipulation of route targets and import/export policies within the VRF configurations456.

• References:

R1

router ospf 10

redistribute static

int et0/0

ip ospf hello-interval 5

ip ospf dead-interval 10

ip ospf cost 15

ip ospf 10 area 0

copy run start

R2

router ospf 10

redistribute static

int et0/0

ip ospf hello-interval 5

ip ospf dead-interval 10

ip ospf cost 15

ip ospf 10 area 0

copy run start

 To address the issue of BGP session flapping between ISP A and ISP B, the networking team at ISP A should implement BGP route dampening. This feature helps stabilize the network by suppressing the advertisement of flapping routes. The command bgp dampening 15 700 1500 30 will set the parameters for route dampening, where routes that flap will be suppressed for 30 minutes. This action will prevent the constant advertisement and withdrawal of unstable routes, thus improving the stability of the network. References := For further details on BGP route dampening and its configuration, the Implementing and Operating Cisco Service Provider Network Core Technologies (SPCOR) course materials and Cisco’s official documentation provide comprehensive guidance.

When creating new Cisco MPLS TE tunnels, the headend router sends a Path message to reserve bandwidth on the path to the tunnel’s tailend router. The Path message is part of the RSVP (Resource Reservation Protocol) used in signaling and establishing MPLS TE tunnels. It carries information about the requested resources and desired parameters for the tunnel123. References: Configuring MPLS TE RSVP, MPLS TE RSVP-TE, MPLS TE Theory.

Model-driven telemetry (MDT) in a service provider environment uses a push model to send data to network monitoring tools. This method is beneficial because it allows for the streaming of data from network devices to monitoring tools in real-time, using reliable transport mechanisms. This approach is more efficient than traditional polling methods like SNMP, as it can provide faster and more granular data updates, which is crucial for maintaining network performance and reliability123.

References: Implementing and Operating Cisco Service Provider Network Core Technologies (SPCOR)

 Transport Layer Security (TLS) is essential for securing RESTCONF communications on network devices. TLS provides a secure channel with encryption, ensuring that the data exchanged between the client and server remains private and integral. For RESTCONF to utilize TLS, it requires proper certificates for authentication. These certificates confirm the identity of the devices involved in the communication, preventing man-in-the-middle attacks and unauthorized access2.

References := Programmability Configuration Guide, Cisco IOS XE Amsterdam 17.1.x - RESTCONF Protocol2.

In the context of Cisco’s Implementing and Operating Service Provider Network Core Technologies, the UCS Series is typically where OpenStack components would be hosted. OpenStack is a cloud operating system that controls large pools of compute, storage, and networking resources throughout a data center, all managed through a dashboard that gives administrators control while empowering their users to provision resources through a web interface.

References: Cisco SPCOR training materials and documentation provide detailed information on the implementation and operation of service provider technologies, including the hosting of OpenStack components on the UCS Series.

A SYN flood is a type of denial-of-service (DoS) attack where an attacker sends a large number of SYN requests to a target server, overwhelming its resources and preventing legitimate connections. The attacker does not complete the TCP handshake, leaving the server in a half-open state.

 The configuration in Option D is correct for implementing BGP selective prefix suppression according to the requirements. The “aggregate-address” command is used to configure the advertisement of the summarized route 10.16.0.0/21, and the “suppress-map” option allows for selective suppression of specific prefixes, in this case, 10.16.6.0/24. References: Implementing and Operating Cisco Service Provider Network Core Technologies (SPCOR) - Cisco SPCOR Training & Certification

 Implementing CSC VPN services for a new backbone carrier provides several benefits. Firstly, it maintains a single backbone network, which simplifies the VPN implementation to customers (A). This eliminates the need for each Level 2 carrier to create and maintain a separate backbone network, thus lowering maintenance costs and simplifying management operations. Secondly, it supports a scalable growth strategy that services multiple customers efficiently (D). The Level 1 carrier can use one backbone network to provide VPN and Internet services for multiple Level 2 carriers, increasing revenues and efficiency.

References: The benefits of implementing CSC VPN services are detailed in the Huawei IP Encyclopedia, which explains the Carrier’s Carrier (CSC) networking solution in BGP/MPLS IP VPN2.

In OSPF, the election of the designated router (DR) and backup designated router (BDR) is based on the OSPF network type. The network types include:

• Broadcast: This is the default network type for Ethernet interfaces. In a broadcast network, OSPF elects a DR and BDR. All other routers become DROTHERs. To prevent the election of a DR/BDR, you can configure the interface as non-broadcast (NBMA) using the ip ospf network non-broadcast command.
• Point-to-Point: This network type is used for point-to-point links (e.g., serial links). There is no DR/BDR election in point-to-point networks.
• Point-to-Multipoint: This network type is used for point-to-multipoint links (e.g., Frame Relay). There is no DR/BDR election in point-to-multipoint networks.
• Point-to-Multipoint Non-Broadcast: Similar to point-to-multipoint, but explicitly configured as non-broadcast. There is no DR/BDR election in point-to-multipoint non-broadcast networks.
• Loopback: Loopback interfaces are always treated as point-to-point.
• Virtual-Link: Used for OSPF virtual links.
• Sham-Link: Used for OSPF sham links.
• Demand Circuit: Used for demand circuits (e.g., ISDN).
• Non-Broadcast: Explicitly configured as non-broadcast. There is no DR/BDR election in non-broadcast networks.

References:

• Implementing and Operating Cisco Service Provider Network Core Technologies (SPCOR) v1.0
• Cisco Learning Network Store - SPCOR Training

In the given scenario, the goal is to restrict users on the network between R1 and R2 from accessing the external network through R5, while still allowing them access to all resources within the administrative domain. The correct approach is to configure an Access Control List (ACL) that permits traffic to all internal networks and denies traffic to any external address. This ACL should be applied to the R2 interface that connects to R1 in the ingress direction. By doing so, traffic originating from users between R1 and R2 destined for external networks will be blocked, while internal traffic will be allowed.

References: This explanation is derived from the Implementing and Operating Cisco Service Provider Network Core Technologies (SPCOR) study materials, which cover the configuration and application of ACLs in a service provider network environment.

 In the given configuration, “tacacs-server host 192.168.1.2 single-connection” indicates that Router 1 will maintain a single connection to the TACACS+ server at IP address 192.168.1.2 for multiple authorization requests instead of opening a new connection for each request. This can be efficient in scenarios where there are frequent authorization requests as it reduces the overhead associated with establishing a new TCP connection each time.

References := Implementing and Operating Cisco Service Provider Network Core Technologies

To secure REST APIs, a network administrator should ensure that user sessions are authenticated and that the appropriate privilege level is provided for each user. This means that each API request should come with authentication credentials, and the server should validate these credentials for every request. This approach helps to maintain the stateless nature of REST APIs and ensures that only authorized users can access or modify resources. References: Best practices for securing REST APIs include using HTTPS, token-based authentication, and proper validation of input parameters to prevent common security vulnerabilities.

The OSPF adjacency issue between R1 and R2 is likely due to mismatched OSPF network types or hello/dead interval settings. The command ip ospf network point-to-point is used on point-to-point network types, which do not require matching hello/dead intervals, thus allowing OSPF adjacency to form even if these intervals are mismatched on the two routers. References: = Implementing and Operating Cisco Service Provider Network Core Technologies course materials. (

If RC is a stub router in an OSPF network, it requires a default route to be injected so that it can send traffic outside the OSPF domain. In OSPF, stub routers do not have any routes external to the OSPF domain in their routing tables. To allow these routers to reach networks outside of their OSPF domain, a default route should be injected into the stub area by the Area Border Router (ABR). This allows all routers in the stub area, including RC, to forward traffic for unknown destinations to the ABR, which then forwards it appropriately. References: Implementing and Operating Cisco Service Provider Network Core Technologies source documents or study guide

• The Forward Error Correction (FEC) field within the OTN (Optical Transport Network) signal structure is responsible for error correction. When data arrives at the receiver, the FEC field helps correct any errors that may have occurred during transmission. It enhances the reliability of optical communication by detecting and rectifying errors.
• References: Implementing and Operating Cisco Service Provider Network Core Technologies course materials.

Wavelength-division multiplexing (WDM) is a technology which multiplexes a number of optical carrier signals onto a single fiber [1], using different wavelengths of light to carry different signals. This allows for a greater capacity for data transfer and enables the addition of new wavelengths in a fiber-optic network

• Option A corresponds to the desired configuration. It uses an access-list to permit IGMP joins for the specific multicast group 239.10.10.10 from the source 172.20.20.3.
• Options B, C, and D do not match the desired configuration. They either allow all IGMP traffic or do not specify the correct source and group addresses.

References: Implementing and Operating Cisco Service Provider Network Core Technologies (SPCOR) source book

 The MPLS LSP ping is the utility that must be used to locate MPLS faults. It is specifically designed to troubleshoot Multiprotocol Label Switching (MPLS) by sending a ping through the MPLS network to verify the path and identify any issues.

References: Cisco provides a guide on MPLS Troubleshooting

Stateful (It has 1: N translation, It uses address overloading, It conservers IPv4 addresses)

Stateless (It is limited on the number of endpoints, It mandates IPv4-translatable IPv6 address allocation)

Segment routing prefix segments are linked to a prefix SID that is globally unique within the segment routing domain. This means that each prefix SID identifies a specific prefix in the network and is unique across the entire segment routing-enabled domain, ensuring that the path to the prefix can be identified and used by any node within the domain1. References: Introduction to Segment Routing - Cisco Learning Network2, ASR9000/XR Introduction to Segment Routing - Cisco Community3, About Segment Routing - Cisco Content Hub

 To prevent packets from being forwarded beyond the service provider domain when the Label Switched Path (LSP) is down, the engineer must configure a private IP address as the destination address of the headend router of Cisco MPLS Traffic Engineering (TE). This ensures that if the LSP fails, the packets will not be routable over the public internet, thus containing them within the service provider’s network.

References := Implementing and Operating Cisco Service Provider Network Core Technologies (SPCOR) documentation provides guidelines on MPLS TE configuration, including the use of private IP addresses for headend routers to maintain traffic within the service provider domain. This practice is aligned with the principles of traffic engineering and network containment for service providers.

 When implementing Nonstop Routing (NSR) High Availability on an MPLS Provider Edge (PE) router, it’s important to consider that NSR generally consumes more memory and CPU resources than Nonstop Forwarding (NSF) because it needs to maintain a stateful switchover capability. Additionally, NSR requires routing protocol extensions to ensure that the state information is correctly synchronized between the active and standby routers, allowing for seamless failover without session loss. This ensures continuous packet forwarding even during a switchover event.

To view login history for users who activated a session, the network administrator can use the show netconf-yang sessions command. This command provides information about active NETCONF/YANG sessions, including the login times for each user.

References:

• Cisco Community - Any command to see login history using CLI
• WinTips.org - How to View User Login History in Windows 10/11
• nixCraft - Linux Display Date And Time Of Login

https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/prog/configuration/167/b_167_programmability_cg/configuring_yang_datamodel.html

 A Virtual Network Function (VNF) role refers to a network function that is executed in software and can be deployed on a Network Functions Virtualization Infrastructure (NFVI). A firewall serves as a VNF role because it performs network functions, such as filtering traffic and security management, in software form rather than as a physical device.

References: Implementing and Operating Cisco Service Provider Network Core Technologies source documents or study guide.

To complete the launch of the new internet service, ISP_A needs to ensure that routes are shared between different VRFs for Customer_A and Customer_B. Importing route-target 62:101 into the customer VRFs on R1 and R3 allows for the exchange of routes between these VRFs, facilitating the necessary connectivity for the new service. References := Cisco SPCOR

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The Adjacency-SID sub-TLV extension is advertised within TLV-22 (Extended IS Reachability) to label a specific link in a segment routing domain. This allows for the identification and utilization of specific paths or links within the network, facilitating more efficient routing and traffic management. References := Implementing and Operating Cisco Service Provider Network Core Technologies

The Cisco MPLS TE forwarding adjacency feature allows a TE tunnel to be advertised into the IGP, effectively making the tunnel appear as a network link in the IGP topology. This integration helps in the optimal utilization of the TE tunnel by other routers for IP routing purposes.

https://www.cisco.com/c/en/us/p roducts/collateral/switches/nexus-9000-series-switches/guide-c07-734107.html

The configuration applies a QoS policy to the pos0/2/0/0 interface, which affects traffic as it exits the interface. The policy map “ciscopolicy” references the class map “ciscotest”, where traffic matching the class map criteria will be remarked. The command set precedence 1 within the class map “ciscotest” indicates that the traffic will be remarked to IP precedence 1. Therefore, the correct effect of this configuration is that traffic identified by the “ciscotest” class map will be remarked from its original IP precedence to IP precedence 1 when it exits the pos0/2/0/0 interface.

References: = This explanation is based on the QoS configuration practices as outlined in the Implementing and Operating Cisco Service Provider Network Core Technologies (SPCOR) course materials.

• References:

 NSO, or Network Services Orchestrator, provides full lifecycle management of devices and services in a network. It is designed to automate the service lifecycle from design and creation through deployment and decommissioning, without the need for manual intervention. This includes configuration, activation, updating, and ultimately, removal of services.

References: The role of NSO is detailed in the Cisco Crosswork Network Services Orchestrator (NSO) documentation

To configure multi-topology IS-IS for IPv6, the router must be configured with the ipv6 router isis command under the interface configuration mode. This command enables IS-IS for IPv6 on the interface. The ipv6 router isis command is used to enable IS-IS for IPv6 on an interface. The multi-topology keyword specifies that the interface will participate in multiple topologies. The level-1 and level-2 keywords specify the IS-IS levels for which the interface will participate. In this case, we want the interface to participate in both Level 1 and Level 2 topologies, so we use both keywords. 

 RFC 5305 extends the IS-IS protocol for traffic engineering by specifying new information that an Intermediate System (router) can place in Link State Protocol Data Units (LSPs). Sub-TLV type 10 of the extended IS-IS reachability TLV type 22 is used to specify the maximum reservable link bandwidth. This is an important parameter for traffic engineering as it defines the amount of bandwidth that can be reserved by traffic engineering algorithms for use in constrained-path computations for MPLS traffic engineering Label Switched Paths (LSPs). References: RFC 53051.

• In Cisco Unified MPLS, BGP (Border Gateway Protocol) is used to transport labels along with network layer reachability information. RFC 3107 defines BGP/MPLS IP Virtual Private Networks (VPNs) and allows BGP to carry MPLS labels, enhancing scalability and flexibility in MPLS networks.

References

1: Cisco. “Implementing and Operating Cisco Service Provider Network Core Technologies (SPCOR).” Link

The correct configuration for MPLS LDP synchronization with OSPF process 1 on router R1 is to use the command mpls ldp igp sync holddown 60 under the OSPF process configuration. This ensures that the MPLS LDP synchronization is enabled and held for 60 seconds with OSPF process 1, which helps prevent black holes in MPLS networks during the convergence process by ensuring that routes are not advertised until LDP is fully operational and labels have been exchanged between adjacent routers.

References:

• Implementing and Operating Cisco Service Provider Network Core Technologies (SPCOR) - Cisco SPCOR
• Additional resources on Cisco’s Service Provider training: Cisco Service Provider Training

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 In a Unified MPLS routing architecture with partitioned IGP domains, it is essential to ensure that the iBGP Labeled Unicast address families are correctly configured to facilitate the exchange of VPNv4 routes directly between PE routers. In this case, ABR R102 should be configured with the address family-level configuration depicted in Option A to support this architecture. This configuration ensures that R101 can peer with both R102 and R103, and similarly, R201 can peer with R202 and R203 using iBGP Labeled Unicast address families. References := Implementing and Operating Cisco Service Provider Network Core Technologies

 The BFD (Bidirectional Forwarding Detection) interval configuration on an interface is automatically disconnected when the BFD-configured subinterface is removed. This is because BFD sessions are tied to the specific subinterface, and removing it will terminate the BFD session associated with that subinterface.

References: The information is based on the Implementing and Operating Cisco Service Provider Network Core Technologies (SPCOR) course, which covers the configuration, verification, troubleshooting, and optimization of Service Provider IP network infrastructures, including BFD implementation

To inject a default route into the MP-BGP address family for a dedicated VRF, you would typically need to:

• Configure a static default route in the VRF using the ip route vrf 0.0.0.0 0.0.0.0  command.
• Redistribute the static route into BGP using the redistribute static command under the BGP VRF configuration.

 IP over ATM (IPoATM) and MPLS offer significant benefits over traditional ATM backbone networks, primarily due to their support for variable-length packets. Unlike ATM, which uses fixed-length cells, IPoATM and MPLS can handle packets of varying sizes, making them more efficient for carrying IP traffic. This efficiency comes from reduced overhead and better bandwidth utilization, as IP packets don’t need to be segmented and reassembled, avoiding the cell-padding issues inherent in ATM’s fixed-size cells1.

References: Performance Comparison of MPLS and ATM Based Networks - EUDL1.

To ensure multiple paths toward the hosting-as-a-service solution and basic protection against traffic black-holing in case of link failure, the engineering team should:

• B. Configure the fast-reroute per-prefix command for the IS-IS protocol in the MPLS network. This action enables fast reroute, which is a mechanism to quickly switch over to a backup path in case the primary path fails, without waiting for the routing protocol to converge.
• D. Configure the mpls ldp sync command in the MPLS network with the BGP additional-paths receive and additional-paths send options. MPLS LDP (Label Distribution Protocol) synchronization ensures that a label-switched path (LSP) is not used for forwarding traffic until all routers along the path have signaled that they have label information for that LSP. The BGP additional-paths feature allows for the advertisement of multiple paths for the same prefix, providing path diversity and redundancy.

https://www.cisco.com/c/en/us/support/docs/quality-of-service-qos/qos-policing/19645-policevsshape.html

 The Network Services Orchestrator (NSO) is designed to allow service providers to automate network operations efficiently. It provides a single, well-defined API that enables integration across various network environments. NSO’s capabilities include zero-touch telemetry, machine learning intuition, open APIs, and automated actions, which facilitate a simpler and more efficient network operation experience. This makes it an ideal choice for service providers looking to plan, optimize, and achieve closed-loop operations within their networks.

References := The information is based on the Implementing and Operating Cisco Service Provider Network Core Technologies (SPCOR) training and certification resources, which offer a deep dive into service provider technologies, including core architecture, services, networking, automation, quality of services, security, and network assurance123.

• The configuration in Option A is used to implement URPF in loose mode on the GigabitEthernet0/1 interface.
• Loose mode allows the router to check for any route back to the source, not necessarily the best route.
• By enabling URPF, the router ensures that incoming packets have a valid return path in the routing table.
• This helps prevent IP spoofing and limits malicious traffic on the network.

References:

• Implementing and Operating Cisco Service Provider Network Core Technologies
• On-Demand E-Learning

To avoid advertising the same routes back to their sources when using RIP as the routing protocol between multiple PEs and CEs, the network engineer should define VRFs (Virtual Routing and Forwarding) on each device. VRFs allow for traffic separation by creating separate routing tables for different VPNs or customers. By using VRFs, each CE-PE link can be associated with a specific VRF, ensuring that routes are not inadvertently advertised back to their sources. Other options (A, B, and D) are not directly related to this specific requirement. References: Implementing and Operating Cisco Service Provider Network Core Technologies source documents or study guide.

https://community.cisco.com/t5/mpls/cisco-xr-rpl-destination-vs-destination-prefix/td-p/4587693

Network Services Orchestrator (NSO) uses the YANG (Yet Another Next Generation) modeling language to provide a standardized way to automate network devices. YANG provides a powerful schema to model configuration and state data for network elements, which NSO leverages for service automation and orchestration.

References: Cisco Crosswork Network Services Orchestrator (NSO) - Cisco2.

The configuration shown indicates that R1 has been configured to support Label Distribution Protocol (LDP) graceful restart. This means that R1 will maintain the forwarding state during an LDP restart, allowing it to continue forwarding packets along known routes while it re-establishes LDP neighbors/peers. This ensures minimal disruption to traffic flow during such events. References: Implementing and Operating Cisco Service Provider Network Core Technologies source documents or study guide

To enable LDP session protection for LDP neighbors within each VRF, the engineer should configure LDP session protection within the individual VRFs. This ensures that LDP sessions are protected at the VRF level, providing security and stability for MPLS-based services. By enabling LDP session protection within each VRF, the router will take appropriate actions to protect LDP sessions against misbehaving neighbors or potential attacks. References: Implementing and Operating Cisco Service Provider Network Core Technologies (SPCOR) v1.0

The configuration should include a class-map that matches the ICMP traffic destined for the web server’s IP address. This can be achieved by using an access control list (ACL) within the class-map to match the ICMP traffic. Then, a policy-map should be applied that sets the next hop to the IP address of the new security appliance. This policy-map is then applied to the appropriate interface on router R2 using the service-policy command.

References: The Implementing and Operating Cisco Service Provider Network Core Technologies (SPCOR) course provides detailed information on configuring class-maps and policy-maps for traffic redirection. Specifically, it covers topics related to VPLS services and DDoS protection, which are relevant to the scenario presented in the question12. The course materials and official Cisco documentation serve as the primary references for this solution.

 BSR (Bootstrap Router) is used in PIM-SM networks to automate the distribution of group-to-RP mappings. In this scenario where devices need to dynamically learn about Rendezvous Points (RPs), BSR would be appropriate as it allows routers to automatically discover RP candidates and convey that information throughout the PIM domain. References := Cisco

The IPv4 address family configuration under neighbor configuration-mode must be removed. The exhibit shows the configuration of a BGP neighborship between an ASBR and a directly connected BGP speaker. The ASBR is running Cisco IOS XR. The neighbor is configured with the IPv4 address family, which is not supported on Cisco IOS XR. To establish the BGP neighborship, the IPv4 address family configuration must be removed.

https://www.cisco.com/c/en/us/td/docs/routers/xr12000/software/xr12k_r41/routing/configuration/guide/routing_cg41xr12k_chapter1.html

 mVPN (Multicast Virtual Private Network) is designed to support the efficient transport of multicast streams across a Layer 3 VPN. It enables service providers to use their existing MPLS networks to transport multicast traffic, allowing for scalable and manageable multicast delivery without requiring a separate network infrastructure. References: Implementing and Operating Cisco Service Provider Network Core Technologies

Here is the solution:

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The issue is occurring in OSPF stub area 100 where the Ethernet link is down between routers RX and RY due to a cut fiber, leading to dropped traffic from CE site A to the hub site. Changing the OSPF area 100 type to stub on RZ can resolve these issues. In a stub area, OSPF routers use a default route to forward traffic to destinations outside the area, reducing the size of their routing tables. This would allow traffic from CE site A to be routed through RZ when the direct link between RX and RY is down.

References: Implementing and Operating Cisco Service Provider Network Core Technologies (SPCOR) - Cisco SPCOR Training

RSVP tear messages are used to clear the PATH or RESERVATION states on a router instantaneously, which enables the reuse of resources on the router for other requests. This is essential in MPLS Traffic Engineering where efficient resource management is crucial for maintaining network performance and stability.

References: The explanation is based on the information provided in the Cisco Press article on MPLS TE Theory

In an EVPN operation, the PE (Provider Edge) router determines and advertises Ethernet segment reachability by discovering remote ESIs (Ethernet Segment Identifiers) and determining their redundancy mode (all-active or single-active). This is crucial in multihoming scenarios where the PE needs to auto-discover remote PEs and the corresponding redundancy mode. In case of segment failures, PEs withdraw the routes used at this stage to trigger fast convergence by signaling a MAC mass withdrawal on remote PEs3.

References:

• Cisco, “EVPN Configuration Guide for Cisco 8000 Series Routers, IOS XR Release 7.11.x”
• Huawei, “Overview of EVPN - New IP Technologies”

Router R1 establishes TCP connections that are authenticated with an MD5 password. In the context of BGP (Border Gateway Protocol), TCP is used for establishing connections, and MD5 passwords can be used for authentication to enhance security.

In the context of OSPF multiarea implementation, adjacency issues can arise due to network type mismatches or area boundary discrepancies. The command “ip ospf network point-to-point” is used on interface G0/1 to specify the OSPF network type as point-to-point. This configuration facilitates OSPF neighbor establishment over a direct connection between two routers, eliminating the need for a designated router (DR) or backup designated router (BDR), and resolving adjacency issues in the new area. References: Implementing and Operating Cisco Service Provider Network Core Technologies source documents or study guide

https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/ iproute_ospf/configuration/xe-16/iro-xe-16-book/iro-multi-area-adj-xe.html

 MPLS LDP (Label Distribution Protocol) is used for label distribution in MPLS networks. When making changes to the LDP configuration, it’s essential to ensure that the changes do not disrupt existing LDP sessions. In this scenario, the network administrator implemented MPLS LDP changes on the PE-A LSR (Label Switching Router) device, and the goal is to prevent any disruption to LDP peers.

The MPLS LDP Non-Stop Routing (NSR) feature allows LDP sessions to survive control-plane switchover events without interruption. When NSR is enabled, the LDP session state information is synchronized between the active and standby control planes. If the active control plane fails, the standby control plane takes over seamlessly, and LDP sessions continue without interruption.

https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/msp/configuration/xe-3s/mp-ha-xe-3s-book/mp-nsr-ldp-supp.pdf

• Configure an IP domain name: An IP domain name is essential for generating RSA keys needed for SSH. The RSA keys are part of the crypto key configuration, which is necessary to enable SSH on the router. This step ensures that users are authenticated via the SSH protocol when accessing the network remotely.
• Configure crypto keys: The crypto keys are crucial for secure communication. The engineer should generate RSA keys using the configured IP domain name. These keys will be used for encryption and authentication during SSH sessions.

The other options (B, D, and E) are not directly related to completing the SSH configuration for secure remote access. Therefore, the correct answers are A and C.

References:

• Implementing and Operating Cisco Service Provider Network Core Technologies

 MPLS TE tunnels are designed to optimize the flow of network traffic by mapping it onto specific paths based on resource requirements. Two key characteristics of MPLS TE tunnels are:

• RSVP for Bandwidth Reservation: MPLS TE tunnels use the Resource Reservation Protocol (RSVP) to reserve the necessary bandwidth for the tunnel, ensuring that the required resources are available for the data that will flow through it12.
• Unidirectional Flow: These tunnels are unidirectional, meaning they are established from a source to a destination and do not inherently support traffic in the reverse direction. This is because each MPLS TE tunnel is associated with a label-switched path (LSP) that is specifically set up for traffic flowing in one direction

The correct configuration to apply to the ASN 65001 border router is Option C. This configuration uses a route policy named PEER-AS65002-IN, which is applied to incoming routes from ASN 65002. The policy denies routes that have traversed 10 or more ASNs or have looped through ASN 65001. It also assigns a community value of 65001:200 to routes matching the prefix 2001:db8:aaaa::/48, which aligns with the conditions specified.

References: Implementing and Operating Cisco Service Provider Network Core Technologies (SPCOR v1.0); Cisco SPCOR Training & Certification.

 In OSPF, the election of the designated router (DR) and backup designated router (BDR) is based on the OSPF network type. The network types include:

• Broadcast: This is the default network type for Ethernet interfaces. In a broadcast network, OSPF elects a DR and BDR. All other routers become DROTHERs. To prevent the election of a DR/BDR, you can configure the interface as non-broadcast (NBMA) using the ip ospf network non-broadcast command.
• Point-to-Point: This network type is used for point-to-point links (e.g., serial links). There is no DR/BDR election in point-to-point networks.
• Point-to-Multipoint: This network type is used for point-to-multipoint links (e.g., Frame Relay). There is no DR/BDR election in point-to-multipoint networks.
• Point-to-Multipoint Non-Broadcast: Similar to point-to-multipoint, but explicitly configured as non-broadcast. There is no DR/BDR election in point-to-multipoint non-broadcast networks.
• Loopback: Loopback interfaces are always treated as point-to-point.
• Virtual-Link: Used for OSPF virtual links.
• Sham-Link: Used for OSPF sham links.
• Demand Circuit: Used for demand circuits (e.g., ISDN).
• Non-Broadcast: Explicitly configured as non-broadcast. There is no DR/BDR election in non-broadcast networks.

References:

• Implementing and Operating Cisco Service Provider Network Core Technologies (SPCOR) v1.0

 In a multi-vendor environment with PIM-SM, the Bootstrap Router (BSR) mechanism is used for devices to dynamically learn the Rendezvous Point (RP). BSR is a protocol feature that automates the dissemination of RP information in a PIM domain. This feature allows routers to automatically discover the RP set in use, which simplifies configuration and management compared to static RP configurations or Auto-RP. References: Implementing and Operating Cisco Service Provider Network Core Technologies source documents or study guide

The correct configuration to reduce LDP LIB size and advertise label bindings for the /32 loopback IP space only is to use an IP prefix-list that specifies the /32 prefix length and then configure MPLS LDP to allocate labels for these prefixes. The ip prefix-list LOOPBACKS seq 5 permit 0.0.0.0/0 le 32 command creates a prefix-list named LOOPBACKS that allows any IP address with a prefix length less than or equal to 32. The mpls ldp label allocate global prefix-list LOOPBACKS command then instructs the router to allocate labels for all prefixes permitted by the LOOPBACKS prefix-list, which in this case, would be all /32 prefixes. References: The explanation is based on the concepts covered in the SPCOR course, specifically the sections on MPLS LDP configuration and optimization. For more detailed information, refer to the official Cisco SPCOR course materials and documentation available at Cisco’s official training page.

To collect the required traffic statistics, the network engineer must configure the router to capture specific data points. The configurations in Option A and Option D align with these requirements. Option A involves configuring the router to collect IPv4 protocol, source address, destination address, application name, interface output, IPv4 source-prefix, IPv4 destination-prefix, counter bytes, flow direction, and transport tcp-flags. Option D involves setting the cache-period timer active to 20 seconds, which aligns with the CPU limit of processing samples that are a maximum of 20 seconds long.

References := Implementing and Operating Cisco Service Provider Network Core Technologies (SPCOR) v1.0

 DWDM, or Dense Wavelength Division Multiplexing, uses different wavelengths of light to combine multiple optical signals. This method allows for the transmission of various data streams simultaneously over a single optical fiber. By using closely spaced wavelengths, DWDM can fit more channels onto a single fiber, significantly increasing the capacity and efficiency of fiber-optic networks.

References: The explanation is based on the information available from the web search results on DWDM, which aligns with the principles outlined in the Cisco Service Provider source book. 

 The number “2” in the SNMP server configuration “snmp-server community ciscotest ro 2” refers to the numeric name of the Access Control List (ACL) that contains the list of SNMP managers with access to the agent. In this context, “ro” stands for read-only access, meaning that SNMP managers can only read but not modify data on the device. The ACL identified by number “2” specifies which SNMP managers are authorized to access SNMP data on this device using the community string “ciscotest”.

References: Implementing and Operating Cisco Service Provider Network Core Technologies source documents or study guide.

 The issue likely lies in the customer platforms’ default policy, which restricts E-BGP route exchange. References: Implementing and Operating Cisco Service Provider Network Core Technologies (SPCOR) course materials.

https://www.cisco.com/c/en/us/td/docs/routers/asr9000/software/asr9k-r6-2/routing/configuration/guide/b-routing-cg-asr9000-62x/b-routing-cg-asr9000-62x_chapter_010.html

The core component of MDT that describes the data streamed to a collector is the encoder. In the context of Microsoft Deployment Toolkit (MDT), the encoder is not explicitly mentioned; however, the concept aligns with the process of creating and capturing images of operating systems, which involves encoding or compiling the necessary data into a deployable image.

In Cisco hardware, when a high bandwidth multicast stream is sent over a Multicast VPN (MVPN), a data Multicast Distribution Tree (MDT) is specifically created for that stream. This data MDT is used in addition to the default MDT, which is used for lower-bandwidth or control traffic. The purpose of the data MDT is to optimize the transmission of high-bandwidth streams through the core of the network, ensuring that the multicast traffic is only sent to those PE routers that have local receivers for the multicast group in question. This mechanism helps in efficiently using network resources and provides a scalable solution for transmitting high-bandwidth multicast streams.

References: The explanation is based on the concepts outlined in the Implementing and Operating Cisco Service Provider Network Core Technologies (SPCOR) course, which covers the configuration, verification, troubleshooting, and optimization of Service Provider IP network infrastructures, including advanced topics like MVPN and MDTs

Option B is the correct answer because it meets all the given requirements. The configuration “snmp-server community comaccess ro 10” allows read-only access for all objects to members of Access-List 10 that use the comaccess community string. The “snmp-server host ABC.com informs version 2c public” command ensures SNMP authentication failure traps are sent to SNMPv2c and then to the host using SNMPv2c with the public community string.

 To prevent an MPLS TE Label Switched Path (LSP) from using any overseas links, an operator would use the explicit path feature. This feature allows the operator to define a specific route for the LSP to follow, which can be configured to exclude paths that traverse overseas links.

• https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/prog/configuration/166/b_166_programmability_cg/netconf_programmability_configuration_guide.html
• https://tools.ietf.org/html/rfc6241

The command nsf ietf helper strict-lsa-checking is used to configure the router to terminate the OSPF graceful restart process if it detects any changes in the LSA during the restart. This ensures that the network remains stable and consistent by preventing the use of outdated or incorrect routing information.

Using verbose knob in above command will list all the hops as below: R1#traceroute mpls multipath ipv4 10.1.5.5 255.255.255.255 verbose https://www.cisco.com/c/en/us/support/docs/multiprotocol-label-switching-mpls/multiprotocol-label-switching-mpls/200097-MPLS-LSP-Multipath-Trace.html

The failure to implement IS-IS multitopology can be attributed to the routing process not supporting extended metrics. Extended metrics are necessary for multitopology routing because they allow for the definition of multiple topologies within the same routing protocol, each with its own set of metrics and paths1.

References:

• Implementing and Operating Cisco Service Provider Network Core Technologies (SPCOR) source documents or study guide

To prevent access from spoofed addresses to the LAN, the engineer should enable Unicast Reverse Path Forwarding (uRPF). uRPF checks the reachability of the source address in packets being forwarded, which helps mitigate issues caused by malformed or forged IP source addresses.

• Option A is correct because it enables uRPF on interface FA0/0 and verifies that the source address is reachable via the outgoing interface, which is essential when the routing is symmetric.
• Option C is also correct as it enables uRPF on interface FA0/1 and allows the source address to be reachable via any interface, accommodating environments with asymmetric routing.

References :=

• Implementing and Operating Cisco Service Provider Network Core Technologies (SPCOR) source book and study guide.

The configuration snippet is for model-driven telemetry on Cisco IOS XR, which involves creating a sensor-group named “cisco” and specifying a YANG model path for telemetry data collection. This configuration is used to stream telemetry data from the router, aligning with option D. References: = Implementing and Operating Cisco Service Provider Network Core Technologies course materials

R1

key chain AUTH_ISIS

key 2

key-string C1sco!

exit

int range et0/0 , et1/0

isis authen key-chain AUTH_ISIS

ip isis

isis metric 15

Copy run start

R2

key chain AUTH_ISIS

key 2

key-string C1sco!

exit

int range et0/0 , et1/0

isis authen key-chain AUTH_ISIS

ip isis

isis metric 20

Copy run start

R3

key chain AUTH_ISIS

key 2

key-string C1sco!

exit

int range et0/0 , et1/0

isis authen key-chain AUTH_ISIS

ip isis

isis metric 25

Copy run start

To ensure that a router advertises only networks with a prefix mask length less than or equal to 21 to its BGP neighbor, the correct configuration is Option A. This involves applying a prefix list that permits updates for networks with the specified prefix length. The prefix list acts as a filter for outgoing route advertisements in BGP, ensuring that only routes that match the criteria are advertised to the neighbor.

Model-driven telemetry (MDT) utilizes YANG models to enable the subscription to specific data items that are streamed from network devices. This allows applications to receive near real-time updates without the need for traditional polling methods. MDT with YANG provides a more efficient and scalable way to monitor network devices by pushing updates to subscribers, which can specify the exact data they require2.

References: Configure Model-driven Telemetry on Cisco IOS-XE Devices with YANG Suite - Cisco2.

In the given architecture, if each area is running its own Interior Gateway Protocol (IGP), Border Gateway Protocol (BGP) must be used to provide an end-to-end Multiprotocol Label Switching (MPLS) Label Switched Path (LSP). This ensures that data packets can traverse through the different IGP areas seamlessly, maintaining connectivity across the entire network.

https://www.cisco.com/c/en/us/support/docs/multiprotocol-label-switching-mpls/mpls/215215-segment-routing -overview-and-migration-g.html

• https://www.cisco.com/c/en/us/support/docs/mpls-vpns/multiprotocol-label-switching-mpls/23986-mpls-vpns-config-example.html
• https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/mp_l3_vpns/configuration/15-mt/mp-l3-vpns-15-mt-book/mp-bgp-mpls-vpns.html

Cisco MPLS TE (Traffic Engineering) tunnels provide a way to optimize traffic routing within an MPLS network. However, there are certain constraints to be aware of:

• QoS-aware tunneling: Unfortunately, Cisco MPLS TE tunnels do not inherently support Quality of Service (QoS) awareness. This means that the tunnels themselves do not directly consider QoS parameters when making routing decisions. QoS policies must be applied separately at the network level, and the TE tunnels do not inherently take QoS into account during path selection.
• Tunnels spanning multiple OSPF areas: Contrary to option A, Cisco MPLS TE tunnels can indeed span multiple OSPF areas. The use of OSPF areas does not inherently restrict the creation of MPLS TE tunnels across area boundaries.
• ISIS metrics: Option B is incorrect. When using ISIS (Intermediate System to Intermediate System) as the Interior Gateway Protocol (IGP), newer-style metrics (such as wide metrics) are supported. Older-style metrics are not the only option.
• Tunnels over IP unnumbered links: Option C is also incorrect. Cisco MPLS TE tunnels can be configured over IP unnumbered links, allowing efficient use of IP addresses.

In summary, the primary constraint is the lack of built-in QoS awareness within MPLS TE tunnels.

References:

• Implementing an MPLS VPN over TE Tunnels - Cisco Support
• Configuring Basic MPLS TE - Cisco NX-OS

In the Pipe model of MPLS QoS, the MPLS EXP bits are set by the Customer Edge (CE) device. This model allows the CE to mark the packets, and these markings are retained throughout the MPLS network until they reach the egress Provider Edge (PE) router. The PE router does not alter the MPLS EXP value, ensuring that the QoS policy applied by the customer is preserved end-to-end.

References: Implementing and Operating Cisco Service Provider Network Core Technologies (SPCOR)

The ttl-security hops 2 command sets the accepted Time to Live (TTL) value for BGP packets received from a neighbor. It is used to protect against BGP session hijacking by ensuring that BGP packets come from an expected number of router hops away. In this case, the command specifies that BGP packets from neighbor 2.2.2.2 must have a TTL of at least 253, which means they can only be 1 hop away (255 - 2 = 253) to be accepted.

References: Implementing and Operating Cisco Service Provider Network Core Technologies (SPCOR) training material1.

The neighbor relationship is down because R2 is operating as a Level 1 router and the two routers are in different areas. In the IS-IS (Intermediate System to Intermediate System) protocol, Level 1 routers exchange routing information with other Level 1 routers in the same area, while Level 2 routers exchange information between areas. Since R1 is configured as a level-2 router and R2 as a level-1 router, they cannot form a neighbor relationship if they are not in the same area. References: Implementing and Operating Cisco Service Provider Network Core Technologies source documents or study guide

 Unicast Reverse Path Forwarding (uRPF) in strict mode ensures that packets are received on the interface that the router would use to forward the return traffic. If a packet is received on an interface that is not the best reverse path, the packet is dropped. This helps mitigate IP address spoofing and DDoS attacks.

The ISIS topology exhibit indicates that all four routers are configured as Level 1-2 routers, which means they can operate in both Level 1 and Level 2 IS-IS areas. This is evident from the net addresses that show a mix of area addresses, allowing for intra-area (Level 1) and inter-area (Level 2) routing. Additionally, R1 and R2 are Level 2 neighbors because they have different area addresses, allowing them to form Level 2 adjacencies and route between different areas.

References: = Implementing and Operating Cisco Service Provider Network Core Technologies course materials. 

The configuration shown in the exhibit is used to disable IP directed-broadcasts on a specific interface of a network device. This is typically done to mitigate smurf attacks, which involve sending a large amount of ICMP echo (ping) traffic to IP broadcast addresses, all having a spoofed source address of the victim’s IP. By disabling IP directed-broadcasts, the network device will not forward packets that are sent to broadcast addresses, thus mitigating this type of DDoS attack. References: Implementing and Operating Cisco Service Provider Network Core Technologies (SPCOR) - Module on Security in the Service Provider Network

 In Cisco IOS XR, to send BGP IPv4 labels to build inter-domain Label Switched Paths (LSPs), the configuration command used is router bgp 65515 neighbor 172.16.70.23 address-family ipv4 labeled-unicast. This command specifies that the router should use the BGP labeled unicast address family for the specified neighbor, which enables the exchange of label information along with the IPv4 routing information, facilitating MPLS LSP creation for inter-domain traffic.

References: Implementing and Operating Cisco Service Provider Network Core Technologies (SPCOR) training materials1.