350-501 Implementing and Operating Cisco Service Provider Network Core Technologies (350-501 SPCOR) Questions and Answers

 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

 To monitor memory consumption and buffer statistics securely on P and PE devices in an MPLS core, especially considering the high CPU usage, the engineering team should implement SNMP version 3 for its security features. Therefore, option A is correct as it specifies SNMP version 3 with authentication. Option B is also correct as it enables traps for memory buffer peak, which is essential for monitoring memory thresholds and ensuring quick response to potential issues.

SNMPv3 is the most secure version of SNMP, providing both security and remote configuration capabilities. The current configuration in the exhibit shows SNMP version 2c, which is less secure. SNMPv3 introduces security features such as authentication, privacy (encryption), and access control to address the vulnerabilities associated with earlier versions of SNMP. By re-configuring to use SNMPv3, the network administrator can enhance the security for SNMP for this configuration. References: Implementing and Operating Cisco Service Provider Network Core Technologies (SPCOR) - Cisco SPCOR Training & Certification

 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.

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.

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)

After a router reload, BGP sessions may fail to re-establish due to incorrect source interface configurations for BGP sessions. Since EBGP multihop has been configured, it’s essential that the BGP session uses the correct source interface for establishing the connection. By configuring the neighbor update-source command with the loopback interface on R2, the BGP session will use the stable loopback address rather than the physical interface, which can change state. This ensures that the BGP session remains stable and is not affected by interface states. References: BGP Troubleshooting Cheat Sheet With Examples - Catchpoint2, BGP session stuck in Idle state after NSRP failover - Juniper Networks3, BGP Session is Disconnected - Network Playbook

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 B: Internet routing through global routing on a PE router means that the PE router performs global routing for internet traffic. This allows the PE router to handle both L3VPN traffic and internet traffic.

Option D: Leaking internet routes from the global table into the L3VPN VRF allows the L3VPN customers to access the internet via the same MPLS backbone. The PE router imports internet routes into the L3VPN VRF, enabling internet access for VPN customers.

IOS XE:

It uses linux-based kernel

It has a separate control plane

IOS:

It is monolithic

It shares memory space

 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.

 The multicast implementation shown in the exhibit indicates that R2 is elected as the RP (Rendezvous Point) for the domain. This is inferred from the configuration commands which show R2 set up as a Bootstrap Router (BSR) candidate. In PIM-SM (Protocol Independent Multicast Sparse Mode), the BSR is responsible for announcing the RP-set to all routers in the PIM domain, and since R2 is the only BSR candidate, it effectively becomes the RP by default unless there are other configurations not shown in the exhibit.

The correct configuration for PE1 to connect AS 200 of the service provider with AS 100 of enterprise ABC using BGP, considering the VRF RT 100:10 is already configured, would involve setting up BGP with the correct neighbor and route distinguisher settings. Option C is likely the correct choice as it specifies the BGP neighbor to be within the enterprise ABC’s AS 100 and includes the address family configuration necessary for VRF-aware BGP sessions. References := The Implementing and Operating Cisco Service Provider Network Core Technologies (SPCOR) course materials provide detailed instructions on configuring BGP in a service provider environment, including the use of VRFs and route distinguishers. For more information, please refer to the official Cisco documentation and course materials related to SPCOR1.

LDP session protection capability is a feature that maintains LDP bindings when a link fails, using LDP Targeted Hellos to protect LDP sessions. Without the specific exhibit, it’s not possible to determine which router has LDP session protection enabled but session hold up is not active.

In the context of configuring L2VPN over MPLS, the xconnect statement is essential. It specifies the peer router and virtual circuit ID, creating the connection between two customer edge routers over the service provider’s MPLS network. Without the xconnect statement, there’s no association between the attachment circuits and pseudowire, leading to the failure of the L2VPN service.

 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.

 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.

The configuration in Option C correctly sets up the interfaces for VLAN tag translation. On interface GigabitEthernet2, the command rewrite ingress tag translate 1-to-1 dot1q 21 changes the incoming VLAN tag from 12 to 21. Conversely, on interface GigabitEthernet3, the command rewrite egress tag translate 1-to-1 dot1q 12 changes the outgoing VLAN tag from 21 to 12. This setup ensures that traffic flowing from R1 to R2 and vice versa has the correct VLAN tags as required.

To direct traffic from R3 to R4 via R1, the weight attribute on R3 can be set higher for the route through R1 compared to other routes. Weight is a Cisco-specific BGP attribute that determines the preferred path when multiple routes to the same destination exist. It is local to the router on which it is configured and not advertised to other BGP peers.

References :=

Implementing and Operating Cisco Service Provider Network Core Technologies (SPCOR) course materials.

 Cisco MPLS Traffic Engineering (TE) tunnels necessitate a link-state routing protocol like OSPF or IS-IS because these protocols use Shortest Path First (SPF) calculations. The tunnel endpoints leverage these SPF calculations to implement the tunnel, ensuring an efficient and optimized path through the network. This is essential for MPLS TE, which aims to optimize network resource utilization and improve traffic distribution across the network.

 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.

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.

To ensure that critical, time-sensitive data from the server on R1 to the host on R3 is always prioritized, especially during congestion, the network engineer should implement a Quality of Service (QoS) strategy that uses strict priority queuing. This QoS mechanism ensures that traffic marked as high priority is transmitted first, while other traffic may be queued or dropped if necessary. Strict priority queuing is designed for scenarios exactly like this, where certain traffic must be guaranteed bandwidth to meet time-sensitive requirements. References := For more detailed information on QoS strategies and classification, refer to the Implementing and Operating Cisco Service Provider Network Core Technologies (SPCOR) course materials, specifically the sections discussing QoS mechanisms and their implementation in service provider networks. Additionally, Cisco’s official documentation on QoS provides comprehensive guidelines on configuring and applying strict priority queuing to ensure bandwidth for critical traffic.

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.

R1

Router bgp 65515

No bgp default ipv4-unicast

Neig 2.2.2.2 remote-as 65516

Nei 2.2.2.2 update-soc loopback0

Nei 2.2.2.2 ebgp-multihop 2

Neig 2.2.2.2 pass C1sc0!

Nei 2000:cc13:cc13:2::1 remote-as 65516

Nei 2000:cc13:cc13:2::1 update-so loopback0

Nei 2000:cc13:cc13:2::1 pass C1sc0!

Nei 2000:cc13:cc13:2::1 ebgp-multihop 2

Address-family ipv4

Neig 2.2.2.2 activate

Address-family ipv6

Nei 2000:cc13:cc13:2::1 activate

Ip route 2.2.2.2 255.255.255.255 192.168.1.2

Ipv6 route 2000:cc13:cc13:2::1/128 2000:cc13:cc13:cc13::2

R2

Router bgp 65516

No bgp default ipv4-unicast

Neig 1.1.1.1 remote-as 65515

Nei 1.1.1.1 update-soc loopback0

Nei 1.1.1.1 pass C1sc0!

Nei 1.1.1.1 ebgp-multihop 2

Nei 2000:cc13:cc13:1::1 remote-as 65515

Nei 2000:cc13:cc13:1::1 update-so loopback0

Nei 2000:cc13:cc13:1::1 pass C1sc0!

Nei 2000:cc13:cc13:1::1 ebgp-multihop 2

Address-family ipv4

Neig 1.1.1.1 activate

Address-family ipv6

Nei 2000:cc13:cc13:1::1 activate

Ip route 1.1.1.1 255.255.255.255 192.168.1.1

Ipv6 route 2000:cc13:cc13:1::1/128 2000:cc13:cc13:cc13::1

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.

The script shown in the exhibit is a REST API call that adds a user with the last name ‘CiscoTest’ to the AAA database on the server located at the IP address 192.168.201.10. This is achieved through a POST request, which is typically used to create or update resources on a server. The script specifies the user details in JSON format, which is a common data format used for API calls.

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. (

The full separation model for Internet access and MPLS L3VPN services is chosen to enable EGP (Exterior Gateway Protocol) and IGP (Interior Gateway Protocol) to operate independently. In this model, the internet access and MPLS L3VPN services are fully separated, ensuring that the two networks do not interfere with each other’s operation. This separation enhances network security, performance, and manageability. References: Implementing and Operating Cisco Service Provider Network Core Technologies source documents or study guide

 The local-as keyword is used in BGP configurations to change the local AS number that is used in the BGP OPEN message when establishing a BGP session with a specific neighbor. In this case, even though the router is configured with AS 65000, it will use AS 65112 when establishing a connection with neighbor 192.168.1.2 due to the local-as keyword configuration. References := Cisco

https://www.cisco.com/c/en/us/support/docs/ip/border-gateway-protocol-bgp/13761-39.html

The configuration shown is for the head-end router of a Cisco MPLS TE tunnel with segment routing. This setup involves commands related to segment routing and MPLS traffic engineering tunnels, such as “mpls traffic-eng tunnels”, “segment-routing mpls”, and “segment-routing prefix-sid-map advertise-local”. These commands configure the head-end router to effectively create and manage TE tunnels using segment routing. References: Implementing and Operating Cisco Service Provider Network Core Technologies (SPCOR) - Cisco SPCOR Training & Certification.

Router 1 is the trigger router in a Remote Triggered Black Hole (RTBH) implementation. In the configuration provided, Router 1 has a static route to null0 for network 192.168.1.0/24 with a tag of 1, which is used to drop traffic destined to this network, effectively mitigating DDoS attacks. The route-map “ddos” matches this tag and sets local preference and community accordingly. The BGP process redistributes this static route based on the “ddos” route-map, signaling other routers in the network to drop traffic destined for the attacked network. References: Implementing and Operating Cisco Service Provider Network Core Technologies (SPCOR) - RTBH section1.

: In this scenario, E-LINE pseudowires are suitable because they create a point-to-point Ethernet connection between the two sites. E-LINE pseudowires are commonly used for point-to-point Ethernet services.

The correct configuration for enabling BGP FlowSpec client function and installation of policies on all local interfaces is flowspec address-family ipv4 install interface-all local. This command configures the router to accept FlowSpec policies from a BGP peer and apply them to all local interfaces. The flowspec keyword enables the BGP FlowSpec client function, address-family ipv4 specifies the address family, and install interface-all local ensures that the policies are installed on all local interfaces. References := Implementing and Operating Cisco Service Provider Network Core Technologies course.

 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.

 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.

The RPL script in the image is used to filter BGP routes based on the AS path. The script includes a condition that checks if the AS path contains ‘7077’ using a regular expression (ios-regex ‘777$’). If this condition is met, the route is passed; otherwise, it would be denied by default. Therefore, this script allows routes from AS 7077 and denies others.

References := For specific references, please consult the Implementing and Operating Cisco Service Provider Network Core Technologies source book or study guide, as I am unable to provide direct links or access content from external websites.

NetFlow provides traceback information by analyzing network traffic. To configure NetFlow for traceback, you need to set up a classification ACL (Access Control List) to identify which type of traffic will be analyzed. This allows NetFlow to focus on specific traffic flows and report relevant information. The classification ACL can be based on various criteria such as source/destination IP addresses, port numbers, or protocols. By defining the classification ACL, you ensure that only the relevant traffic is considered for NetFlow analysis.

The correct action to complete the configuration for connecting two offices via an MPLS L3 VPN is option A. This involves configuring the network 172.16.10.0 and using the redistribute-internal static commands under the BGP address family for Customer_A in the global BGP configuration on R1. In an MPLS L3 VPN, the provider edge (PE) router, which is R1 in this scenario, redistributes customer routes into BGP. The PE router then advertises these routes to other PE routers within the MPLS network using MP-BGP, allowing for the establishment of the VPN.

References :=

Implementing and Operating Cisco Service Provider Network Core Technologies (SPCOR) course materials and official Cisco documentation.

Here is the solution:

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

MPLS TE FRR (Fast ReRoute) provides backup protection by creating a bypass LSP for each protected LSP at each point of local repair. This method allows for rapid switching to the backup path in case of a failure, minimizing traffic loss and disruption.

References :=

Implementing and Operating Cisco Service Provider Network Core Technologies (SPCOR) course materials.

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.

 The issue is that the R2 Serial 1/0 interface is configured with an IP address, but the R1 Serial 1/0 interface is unnumbered. In OSPF, for two routers to form a neighbor relationship, they must be able to communicate on the same subnet. If one interface is unnumbered and the other has an IP address, they won’t be able to form a neighbor relationship, leading to OSPF prefixes missing from the routing table. References: Implementing and Operating Cisco Service Provider Network Core Technologies (SPCOR) - OSPF Configuration Guide

MPLS traffic-engineering tunnels can be configured with dynamic paths or explicitly defined paths across the core network. Tunnel links inherit IGP (Interior Gateway Protocol) metrics by default unless overridden by configurations that specify explicit paths or other criteria for path selection. Dynamic path tunnels use IGP metrics and other parameters like bandwidth availability for automatic path calculation. References: Implementing and Operating Cisco Service Provider Network Core Technologies source documents or study guide

The configuration shown in the exhibit indicates that Router 1 is configured with NETCONF-YANG and has enabled the feature candidate-datastore. This means that Router 1 has a temporary data store where a copy of the running configuration can be manipulated and verified before committing the configuration. This allows administrators to test changes before applying them to the running configuration, reducing the risk of errors that could impact network operations.

SOLUTION:-

R1

Config t

router isis 1

net 49.0001.0010.0001.0101.00

area-password C1sc0!

int et0/0

ip router isis 1

isis authen mode text level-2

isis circuit-type level-2

isis tag 1

int et1/0

ip router isis 1

isis authen mode text level-2

isis circuit-type level-2

isis tag 1

R2

router isis 2

net 49.0001.0010.0002.0202.00

area-password C1sc0!

int et0/0

ip router isis 2

isis authen mode text level-2

isis circuit-type level-2

isis tag 2

int et1/0

ip router isis 2

isis authen mode text level-1

isis circuit-type level-1

isis tag 2

R3

router isis 3

net 49.0001.0010.0003.0303.00

area-password C1sc0!

int et0/0

ip router isis 3

isis authen mode text level-1

isis circuit-type level-1

isis tag 3

int et1/0

ip router isis 3

isis authen mode text level-2

isis circuit-type level-2

isis tag 3

R1 Verification: -

R1

Config t

Ipv6 unicast-routing

Router isis 1

Metric-style wide

Address-family ipv6 unicast

Multi-topology

Int loop0

Ip router isis 1

Ipv6 router isis 1

Isis tag 1

Int et0/0

Ipv6 router isis 1

Int et1/0

Ipv6 router isis 1

R2

Config t

Ipv6 unicast-routing

Router isis 2

Metric-style wide

Address-family ipv6 unicast

Multi-topology

Int loop0

Ip router isis 2

Ipv6 router isis 2

Isis tag 2

Int et0/0

Ipv6 router isis 2

Int et1/0

Ipv6 router isis 2

R3

Config t

Ipv6 unicast-routing

Router isis 3

Metric-style wide

Address-family ipv6 unicast

Multi-topology

Int loop0

Ip router isis 3

Ipv6 router isis 3

Isis tag 3

Int et0/0

Ipv6 router isis 3

Int et1/0

Ipv6 router isis 3

R1 Ipv6 Verification: -

L

R1

Copy run start

R2

Copy run start

R3

Copy run start

The configuration snippet shows a BGP router with AS number 65001. It has a neighbor at IP address 10.10.10.1 with remote AS number 4282, and there is an outbound distribute-list applied to this neighbor relationship (distribute-list 1 out).

The distribute list refers to access list 1, which permits any route with an AS path that starts with the local ASN (permit ^$). This means that only local routes will be advertised to the neighbor at IP address 10.10.10.1; routes from other Autonomous Systems (ASNs) will not be advertised because they would have an AS path starting with another ASN.

 The router RA is configured with the command “ip pim ssm default”. This configuration enables Source-Specific Multicast (SSM) for the default range of 232.0.0.0/8, which is the IPv4 multicast address space reserved for SSM by IANA (Internet Assigned Numbers Authority). In SSM, data traffic is delivered to a specific group of subscribers identified by the combination of both source and multicast addresses, enhancing efficiency and security. References: Implementing and Operating Cisco Service Provider Network Core Technologies

 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

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.

 The configuration sets up a telemetry subscription to collect and send data every 60 seconds, which is indicated by the sample-interval 60000 setting in the configuration. References: For more detailed information, please refer to the official Cisco documentation on Implementing and Operating Cisco Service Provider Network Core Technologies (SPCOR) and the specific section on Telemetry Configuration.

The command “traceroute mpls ipv4 10.20.0.1/32 ttl 4” is used to trace the route that packets take to get from the source to the destination in an MPLS network, specifically for IPv4 addresses with a maximum of 4 hops (Time To Live). This command will provide information on all labels and hop-by-hop IP addresses for the specified destinations, meeting the requirements stated in the question.

References := For more detailed information, you can refer to the Implementing and Operating Cisco Service Provider Network Core Technologies training, which covers the configuration, verification, troubleshooting, and optimization of Service Provider IP network infrastructures, including MPLS operations

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

Ansible is widely recognized as a robust network automation tool that facilitates provisioning, configuration, and management of network devices. It uses simple, human-readable YAML syntax for its playbooks, making it easy to define tasks and orchestrate workflows for automated network operations1.

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.

Cisco MPLS Traffic Engineering (TE) tunnels necessitate a link-state routing protocol like OSPF or IS-IS because these protocols use Shortest Path First (SPF) calculations. The tunnel endpoints leverage these SPF calculations to implement the tunnel, ensuring an efficient and optimized path through the network. This is essential for MPLS TE, which aims to optimize network resource utilization and improve traffic distribution across the network.

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

 To ensure that traffic for the prefix 192.168.1.1/32 travels via the alternate path R6-R5, a route-map with a higher local preference should be applied inbound on R3 for neighbor R6. This will make the path through R6-R5 more preferable, thus meeting the requirement. References := Implementing and Operating Cisco Service Provider Network Core Technologies

The service provider must implement a QoS configuration that includes traffic policing to enforce the contracted bandwidth limits. Option B is the correct choice because it specifies a committed information rate (CIR) of 512 kbps, which matches the customer’s contracted rate. The configuration also includes a burst size that accommodates the Tc value of 125 ms, allowing for brief periods of higher traffic without dropping packets. This setup ensures that under peak conditions, any traffic exceeding the contracted rate is either marked or dropped, thus preventing the customer from exceeding the agreed-upon bandwidth. References := For more detailed information on QoS configurations for Frame Relay networks, refer to the Implementing and Operating Cisco Service Provider Network Core Technologies (SPCOR) course materials, which cover the principles of traffic policing and shaping in service provider environments

 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

The URL in the exhibit is used with REST API to send a message to the APIC (Application Policy Infrastructure Controller) to perform an operation on a managed object or class operator. In Cisco’s ACI (Application Centric Infrastructure), REST API requests are used for managing, configuring, and retrieving data from the APIC. The URL structure typically includes the IP address of the APIC and specific paths that refer to objects or classes within the ACI fabric. References: Implementing and Operating Cisco Service Provider Network Core Technologies source documents or study guide

 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”.

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.

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

The configuration shown in the exhibit enables IP flow information collection on the interface gigabitethernet0/1. This setup is used for network traffic analysis, and when applied, it provides data that includes the source interface of the traffic for traceback analysis. This is useful for identifying the origin of traffic, which can be critical in situations such as security incidents or network troubleshooting.

 In this scenario, BGP is used in the core of the service provider network, while OSPF serves as the PE-CE routing protocol. To ensure communication between CE1 and CE2, which are located in different geographical locations, it’s essential for PE1 and PE2 to share routes. This can be achieved by configuring both PEs to mutually redistribute BGP and OSPF routes within the VRF dedicated for that customer, ensuring seamless communication between both customer endpoints. References: Implementing and Operating Cisco Service Provider Network Core Technologies

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

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. 

 A Multi-Layer control plane, like Cisco’s nLight technology, provides an integrated approach that allows for the automatic provisioning, monitoring, and management of traffic across different network layers, from Layer 0 (optical) to Layer 3 (IP). This integration increases network agility and flexibility while improving network utilization, leading to significant cost savings and more efficient network resiliency solutions2.

 The JSON script in the exhibit configures BGP with a neighbor at IP address 192.168.1.2 that resides in AS (Autonomous System) 65514. In the script,  specifies the neighbor’s IP address, and  indicates the AS number of the neighbor.

The requirement is to redistribute routes with a tag of 80 and IP prefixes other than 192.168.10.20/24 from Level 1 into Level 2, and also to configure route leaking from Level 2 into the Level 1 domain for routes that are tagged with only 50 or 40. Option B, “Add match ip address 152 in route-map redist1-2”, meets the first requirement as it allows all IP prefixes except for the specified one (192.168.10.20/24) to be redistributed from Level-1 to Level-2 when they have a tag of 80.

To prevent packet loss when IGP (Interior Gateway Protocol) and LDP (Label Distribution Protocol) are not synchronized, enabling MPLS LDP IGP synchronization is crucial. This synchronization ensures that the IGP routing protocol (such as OSPF or IS-IS) waits until LDP convergence is completed before advertising labels for MPLS traffic. It helps maintain consistency between the IGP and LDP databases.

 YAML’s readability and straightforward syntax make it an ideal choice for expressing infrastructure as code, which is a core principle in both Ansible and SaltStack for automating and managing IT infrastructure.

 The REST API command shown in the exhibit is a POST request to a specific URL, indicating that it is used to submit data to be processed to a specified resource. In this case, the resource is an XML file named “Descriptions.xml”. POST requests are used when submitting data to be processed by the resource identified by the URI. The nature of the process conducted on the submitted data depends on that particular URI. References: Implementing and Operating Cisco Service Provider Network Core Technologies (SPCOR) - REST API section.

 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

1: graceful restart 2: IGP synchronization 3: session protection 4: targeted-hello accept

 In OSPF, for two routers to form an adjacency, they must have matching MTU sizes on their connecting interfaces. If the MTUs are mismatched, OSPF adjacency will be stuck in the EXSTART/EXCHANGE state because OSPF hello packets will not be exchanged between the routers. In this case, both routers R1 and R2 are stuck in EXCHANGE/EXSTART state due to mismatched MTU sizes as indicated in the exhibit. References: Implementing and Operating Cisco Service Provider Network Core Technologies (SPCOR) - Cisco

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

 BGPsec enhances BGP by adding a layer of security for the AS path attribute. When BGPsec is implemented, updates from eBGP peers include a BGPsec attribute sequence with a public key hash and digital signature. This ensures the authenticity and integrity of the AS path, preventing unauthorized AS numbers from being inserted. References: = Implementing and Operating Cisco Service Provider Network Core Technologies course materials. 

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.

The command “show policy-map control-plane” is used to display the control plane policies applied on a Cisco device, including the statistics related to packets matched by the class-maps of the policy-map. In this context, it helps in troubleshooting by providing detailed insights into how different types of traffic are being processed and controlled as they pass through the control plane.

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.

When configuring the 802.1q VLAN tag, the MTU must be increased by 4 bytes. This is because the 802.1Q tag adds an additional header to the Ethernet frame, which includes information such as the VLAN ID and priority. To accommodate this extra header without fragmenting the packet, the MTU must be increased accordingly2. References: Configure 802.1Q VLAN Tagging, 802.1q and MTU.

 The error message “%CLNS-4-AUTH_FAIL: ISIS: LAN LIIH authentication failed” indicates that there is an authentication failure in the IS-IS routing protocol between routers R1 and R2. In the exhibit, it can be observed that R2 has a state of “UP” for its IS-IS neighbor relationship, while R1 is in “INIT” state. This discrepancy in states indicates an issue with the establishment of the neighbor relationship, which can be attributed to an authentication failure at both Level 1 and Level 2 PDUs as indicated by option B.

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 issue is that router R2 is not installing the network 172.16.33.1/32 in the routing table due to an incorrect access list configuration. The correct answer is option C, which will allow the network to be installed in the routing table by permitting addresses from 172.16.33.0 to 172.16.33.255 with a wildcard mask of 0.0.0.255.

The current access list on R2, “access-list 1 permit 172,16,32,0 0,0,0,255”, only permits addresses from the range of 172,16,32,0 to 172,16,32,255 due to its wildcard mask of “0,.0,.0,.255”. This does not include the address “172,.16,.33,.1”.

 Egress PE NAT via a single centralized router allows L3VPN customers to access the internet. The NAT operation maintains a table that includes a field to identify the inside VRF of a translation. This is crucial for distinguishing between different customer VPNs that may use overlapping IP address spaces. By having this field, the NAT process can correctly associate each internal IP with its respective VRF and outside global IP address1. References: Centralized egress to internet, Egress PE NAT single centralized router.

The configuration in Option C uses a route policy that checks if the MED is equal to 30 and then sets the local-preference to 70. This aligns with the requirement to prioritize routes with a MED of 30 by assigning them a higher local-preference value, which influences the BGP path selection process in favor of these routes.

References := The Implementing and Operating Cisco Service Provider Network Core Technologies (SPCOR) course provides insights into configuring route policies for BGP, which includes setting local-preference based on MED values

 The command “show mpls traffic-engineering tunnels” is used to quickly check the path of a TE (Traffic Engineering) tunnel in a Cisco MPLS core network. This command provides detailed information about each TE tunnel, including its current operational status, configuration details, and the specific path it is taking through the network. References: Implementing and Operating Cisco Service Provider Network Core Technologies source documents or study guide

YANG (Yet Another Next Generation) is a data modeling language used to model configuration and state data of a network. It is used to define the data structure of configuration files and is widely used for network configuration and management. YANG uses containers to categorize related nodes, allowing for a hierarchical organization of the data. Types can be associated with each leaf, but they are not required. Spines are not used in YANG, and it is not a distributed model of nodes.

Packet loops can occur during the configuration of BIDIR-PIM if not all parts of your network support this protocol or are configured correctly for it. If some routers or switches in your network don’t understand or aren’t configured for BIDIR-PIM, they can inadvertently forward packets back into parts of the network they were already in, creating a loop. References: Implementing and Operating Cisco Service Provider Network Core Technologies (SPCOR) - Multicast section.

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.

 The Time to Live (TTL) security mechanism is a lightweight security feature that can protect against CPU and memory resource exhaustion due to a denial-of-service (DoS) attack. It works by setting a limit on the number of hops (TTL value) that BGP packets can traverse. By configuring neighbor 10.163.83.55 ttl-security hops 2, ISP A ensures that BGP packets received from ISP C must have a TTL value of at least 254 when they reach R1, as BGP packets decrement the TTL by 1 with each hop. This effectively prevents spoofing attacks from outside the directly connected network because any packets spoofed from further away would have a TTL that drops below the threshold before reaching R1.

Here is the solution: