350-501 Questions and Answers

 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

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.

The configuration snippet indicates a BGP setup where the neighbor 192.168.1.2 is defined, but not activated for the IPv4 address family. To complete the configuration and allow the exchange of IPv4 routes, the neighbor must be activated under the IPv4 address family. This is done by adding the command address-family ipv4 unicast followed by neighbor 192.168.1.2 activate in the BGP configuration mode.

 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.

 For OSPF, the subnet mask must match between two devices on the same network segment to form an adjacency, as it defines the network’s address range. The hello timer setting is crucial for the OSPF Hello protocol, which is used for neighbor discovery and maintaining neighbor relationships. Finally, the area number must be the same because OSPF uses areas to define a hierarchy within the network, and routers within the same area share routing information.

 The iosxr_command module in Ansible is used to issue commands on remote devices running Cisco IOS XR. This module allows network administrators to execute operational commands on Cisco routers and switches, which is essential for tasks such as retrieving information or applying configuration changes. It is a part of network automation using Ansible, which simplifies the management of network devices by automating repetitive tasks.

 A prefix segment identifier (PSID) is a unique identifier used in Segment Routing (SR) networks. It is locally significant within a specific SR domain. Each PSID corresponds to a specific segment (such as a node or an adjacency) in the SR domain. PSIDs are used to create segment lists that define the path a packet should follow through the network. Unlike globally unique identifiers, PSIDs are only meaningful within the context of a single SR domain.

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 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

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.

 In Segment Routing Traffic Engineering (SR-TE), when defining explicit path hops for devices using IP unnumbered interfaces, the router ID and labels are crucial. The router ID uniquely identifies a router in the network, while labels are used to direct packets along a specific path without relying on IP addresses, which is essential in unnumbered interface scenarios

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.

 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

This configuration sets up policing rules for different protocols including CDP (Cisco Discovery Protocol) and ARP (Address Resolution Protocol), with specific rate limits for invalid packets as well as CDP and ARP protocols. References: Implementing and Operating Cisco Service Provider Network Core Technologies source documents or study guide

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.

 The configuration in the exhibit shows that R1 is configured with “mpls ldp graceful-restart”, which enables LDP Graceful Restart on the router. This means that R1 can support a graceful restart operation on the peer, even if graceful restart is disabled on the peer. This feature allows LDP to recover from failures without affecting the forwarding plane, ensuring network stability and minimal packet loss during failovers.

 To establish MPLS LDP sessions between two routers, both routers must be configured to support MPLS on the interfaces that connect them. The configuration shown for R2 includes enabling MPLS label protocol LDP and configuring interfaces Ethernet1/0 and Ethernet1/1. However, to complete the MPLS LDP session setup, R2 also needs to have MPLS enabled on the interface toward R1. This is done by entering the interface configuration mode for the relevant interface and using the mpls ip command. This command enables MPLS forwarding for IP packets on the interface, which is necessary for LDP to advertise and map labels to the IP routes.

References := The answer is based on the concepts covered in the Implementing and Operating Cisco Service Provider Network Core Technologies (SPCOR) course,

 The issue described involves packets being dropped when sent from the application server to the access site. Since OSPF and BGP peerings are confirmed to be operational, the problem likely lies within the route advertisement. Allowing 172.16.20.1 in the BGP advertisement on R3 by adjusting the route-map will likely resolve the issue, ensuring that traffic destined for 172.16.20.1 is not being inadvertently filtered or blocked.

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.

MPLS LSP ping is a utility for locating faults within an MPLS network, specifically for Label Switched Paths (LSPs). It helps in verifying the LSPs in the MPLS network. The utility sends echo requests to the destination, and if the path is complete, echo replies are received. References := Cisco

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.

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.

When implementing LDP NSF on your network, enabling NSF for the link-state routing protocol in use on the network is essential to ensure continuous forwarding of packets during a failure scenario. Additionally, enabling NSF for BGP ensures that BGP sessions are not dropped during a switchover, maintaining network stability and uptime.

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.

 The ip igmp join-group command is used on a router interface to simulate the presence of an IGMP host for a specific multicast group. By issuing the command ip igmp join-group 239.10.10.10, the router is configured to join the multicast group 239.10.10.10 and will receive multicast traffic for this group. This is useful for testing or when the router itself needs to receive the multicast stream.

 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.

 In the given scenario, to ensure that area 15 traffic from R5 to R1 prefers the route through R4, a multiarea adjacency should be implemented on the link between R2 and R4. The cost can be manipulated to make this path preferred. Multiarea adjacency allows OSPF routers to form adjacencies with routers in other areas, enabling more direct routing of traffic. By adjusting the cost of this adjacency, traffic can be directed preferentially through specific paths.

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.

 To implement a PIM-SSM (Protocol Independent Multicast - Source Specific Multicast) configuration for streaming live traffic across different domains, the network operator must ensure that IGMPv3 (Internet Group Management Protocol version 3) is enabled on R1. IGMPv3 is required for SSM because it allows the receiver to specify the source IP address of the desired traffic, which is a key feature of SSM. The operator would configure IGMPv3 on the interfaces that connect to the users who will be accessing the multicast stream. Additionally, PIM-SSM must be enabled on the router, and the multicast sources and groups must be properly defined.

 The TTL security mechanism is used to protect a router from receiving BGP sessions that are not originated from the expected peer. It drops incoming TCP segments whose TTL value is not equal to or greater than the expected minimum value, thus helping in preventing DoS attacks that could be initiated from an unauthorized source pretending to be a legitimate BGP peer. References := Implementing and Operating Cisco Service Provider Network Core Technologies

The issue of Router 1 failing to establish an OSPF peering with Router 2, and the increase in CPU and memory usage can be attributed to a mismatch in MTU (Maximum Transmission Unit) sizes. In OSPF, for a successful adjacency to be formed, the MTU size on the interfaces that are trying to form this adjacency must match. In this case, changing the MTU to 1524 on Router 1 will make it compatible with Router 2, allowing OSPF peering to be established and customer traffic to pass through successfully.

During the traceback phase of the six-phase approach to service provider security, the action that occurs is tracing the attack flows from the attacked sections of the network toward the network edges. This phase entails identifying the source of the attack by analyzing the path that the attack traffic has taken through the network.

Cisco IOS XE Software is an open and flexible operating system optimized for a variety of network infrastructures. One of its key enhancements over Cisco IOS Software is the support for symmetric multiprocessing (SMP). This allows the operating system to efficiently utilize multiple CPU cores, improving performance and scalability for network services.

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 OSPF, for two routers to establish communication, they must have the same key ID and key value on their interfaces. This ensures secure communication between the OSPF peers. The key ID and value are part of the OSPF authentication mechanism that helps in validating the identity of OSPF peers before exchanging routing information. References: Implementing and Operating Cisco Service Provider Network Core Technologies (SPCOR) - Cisco SPCOR Training & Certification

 In Cisco IOS XR software, the keychain management for BGP is done in the routing configuration mode. This mode allows you to configure keychain parameters such as the key identifier, cryptographic algorithm, and other related settings. The keychain is essential for authentication and secure communication between BGP peers. By configuring the keychain in the routing context, you ensure that BGP sessions use the specified keys for authentication and integrity protection1.

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

The issue of the OSPF domain receiving only the 172.17.1.0/24 route and not the default route 0.0.0.0/0 can be resolved by configuring OSPF to propagate default routes. Let’s take a look at the options:

Option A: The configuration includes the following commands:

router ospf 1

default-information originate

end

This configuration generates a default route into the OSPF domain, which is missing in this scenario.

 The “show cef interface” command is used to display per-interface statistics about Unicast Reverse Path Forwarding (uRPF) drops and suppressed drops. uRPF is a feature that helps to mitigate problems caused by IP address spoofing, and the “show cef interface” command provides detailed information on the interfaces where uRPF is applied, including drop statistics.

 In the context of Cisco IOS XR software, the configuration under Option D is appropriate for adding an interface to a bundle using LACP (Link Aggregation Control Protocol). The configuration specifies two Ten Gigabit Ethernet interfaces (TenGigE0/1/0/5 and TenGigE0/1/0/6) with descriptions indicating they are part of “bundle_1_link”. Both interfaces are assigned to “bundle id 1” with a load interval of 30 seconds, ensuring they are part of the same link aggregation group and share traffic load.

The REST API script in the exhibit is used to configure a VRF (Virtual Routing and Forwarding) instance. In the script,  defines a tenant named “customer”, and  creates a VRF named “customervrf” within that tenant. A VRF allows multiple instances of a routing table to co-exist within the same router at the same time, enabling network paths to be segmented without requiring multiple routers. References: Implementing and Operating Cisco Service Provider Network Core Technologies source documents or study guide.

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.

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.

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.

 In OSPF, for two routers to establish communication, they must have the same key ID and key value on their interfaces. This ensures secure communication between the OSPF peers. The key ID and value are part of the OSPF authentication mechanism that helps in validating the identity of OSPF peers before exchanging routing information. References: Implementing and Operating Cisco Service Provider Network Core Technologies (SPCOR) - Cisco SPCOR Training & Certification

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.

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 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

In IS-IS, to advertise only the network prefixes associated with passive interfaces, the command advertise passive-only under the address family configuration mode is used. This ensures that only the prefixes of passive interfaces are advertised to other IS-IS routers in the network. The passive interface command is used to prevent IS-IS from forming adjacencies over that interface, while still allowing the network prefix of the interface to be included in the IS-IS link-state database.

The configuration creates a class map named WEB which is used to match HTTP traffic. This class map can then be referenced in a policy map to define specific actions for traffic that matches the criteria, such as applying QoS policies or traffic shaping.

 In the context of Implementing and Operating Cisco Service Provider Network Core Technologies, LDP-IGP Synchronization is configured to ensure that the IGP and LDP convergences are synchronized. Option C is correct because it shows the configuration where router ISIS 1 is being configured with MPLS LDP sync, but not on a specific interface, ensuring that LDP is operational on all interfaces where IS-IS is enabled before routes are advertised. References := Cisco

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

 To complete the implementation of the route map “ciscotest” for filtering routes to a BGP peer, the engineer must attach the route map to the BGP neighbor statement in the inbound direction. This will apply the specified filtering criteria to routes received from the BGP neighbor, thereby limiting access to restricted areas within the network as intended by the client. References := The Implementing and Operating Cisco Service Provider Network Core Technologies (SPCOR) course materials discuss the configuration of route maps and their application to BGP neighbors for route filtering purposes

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

The configuration command xconnect 192.168.0.1 12 encapsulation mpls pw-class cisco is used to set up a pseudowire connection to a remote peer at IP address 192.168.0.1 using MPLS encapsulation. The pw-class cisco refers to a pseudowire class named ‘cisco’ that defines the parameters for the MPLS pseudowire. This configuration is part of setting up Layer 2 VPNs, which are often used in service provider networks to extend services such as Ethernet, ATM, or Frame Relay over an MPLS network.

 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.

 When interface Gi0/0/0/2 is shut down for maintenance, the other interfaces’ states are affected based on their current configurations and roles. In this case, Gi0/0/0/0 becomes active because it is next in line to take over the traffic load, ensuring that network service remains uninterrupted. Gi0/0/0/1 remains standby as it was before the shutdown of Gi0/0/0/2.

IntServ (Integrated Services) is a model that allows hosts to report their QoS (Quality of Service) needs to the network. In this model, applications inform the network about their bandwidth requirements and traffic characteristics, enabling the network to reserve resources and provide the requested QoS. References := Implementing and Operating Cisco Service Provider Network Core Technologies

 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.

Here is the solution:

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.

 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

 OSPFv3 is designed to support both IPv4 and IPv6. The message “IPv6 routing not enabled” indicates that IPv6 has not been configured on the router, but this does not prevent OSPFv3 from running for IPv4. The OSPFv3 configuration for IPv4 will still function on the interface FastEthernet0/0 as intended.

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.

 To establish LDP peering with the loopback IP address as its Router ID, both RA and RC need to configure their LDP router IDs to use their respective loopback addresses. This is done by applying the ‘mpls ldp router-id loopback0’ command on both routers. This configuration ensures that LDP peering uses the loopback addresses, which is a requirement for the service-provider core network.

References := This explanation is based on the concepts outlined in Cisco’s Implementing and Operating Service Provider Network Core Technologies (SPCOR) course, which provides in-depth knowledge on service provider infrastructure. For further study, refer to the official Cisco documentation and training materials available on the Cisco Learning Network Store.

1: PIM-DM 2:IGMP 3:PIM-SM 3:shared tree 4:source tree

To filter routes when redistributing OSPF into BGP, you should configure a route map and reference it with the redistribute command.

The route map allows you to apply filtering criteria to the routes being redistributed.

Example configuration:

router bgp 65000

redistribute ospf 1 route-map OSPF-TO-BGP

!

route-map OSPF-TO-BGP permit 10

match ip address prefix-list OSPF-TO-BGP-FILTER

!

ip prefix-list OSPF-TO-BGP-FILTER seq 10 deny 192.168.0.0/24

ip prefix-list OSPF-TO-BGP-FILTER seq 20 permit any

In this scenario, gRPC dial-out mode is being used for telemetry. The receiver with IP address 192.168.1.1 will be assigned one of the subscriptions and will manage the ASR. To configure this, the router needs to use the protocol tcp command. This ensures that telemetry data is streamed out over a TCP connection to the specified receiver. Other options (A, B, and D) are not relevant for this specific use case.

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.

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

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.

YANG (Yet Another Next Generation) is a data modeling language used primarily for the configuration and state data of network elements. It is closely associated with the NETCONF (Network Configuration Protocol) for which it models configuration data. YANG provides schemas that define how data is structured and transported by NETCONF operations. It also shapes the state data of network elements, allowing for a standardized format for representing the operational state of devices. References: YANG is defined in RFCs such as RFC 6020 and RFC 7950, which outline its role in NETCONF operations and its capabilities in modeling both configuration and state data.

 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

 Both options provide a default route pointing to CE-1, allowing CE-2 to access the internet. The specific choice would depend on additional context or requirements not provided in the question.

The SPT threshold set to infinity causes multicast traffic to permanently stay on the shared tree and not switch to the source tree. In multicast routing, the Shortest Path Tree (SPT) threshold determines when a router should switch from receiving multicast traffic on the shared tree to receiving it on a source tree. Setting the SPT threshold to infinity means that the router will always receive multicast traffic on the shared tree

In this scenario, CE1 and CE2 need connectivity to the internet through the ISP connected to PE3. The most straightforward approach is to configure CE1 and CE2 with a static default route pointing to PE3 as the next-hop for internet-bound traffic. This ensures that any traffic destined for the internet will be routed directly to PE3, which is directly connected to the internet. Other options (A, B, and D) involve more complex configurations and are not necessary for this specific task. References: Implementing and Operating Cisco Service Provider Network Core Technologies source documents or study guide

The available PHY modes to implement an IOS XR Gigabit Ethernet interface are MAN (Metropolitan Area Network) and WAN (Wide Area Network). References:

Cisco IOS XR Software Configuration Guide

Cisco ASR 9000 Series Aggregation Services Routers Interface and Hardware Component Configuration Guide

Hr40wan - 10 Gigabit Ethernet WAN PHY Controller Commands on Cisco IOS XR

10-Gigabit Ethernet WAN PHY Controller Commands 

The network operator needs to provide connectivity between two IPv4 and IPv6 dual-stacked networks using specific assigned IPv6 space. NAT46 (Network Address Translation 46) is the appropriate technology for this scenario. It allows translation between IPv4 and IPv6 addresses, enabling communication between the dual-stack networks. NAT46 maps IPv6 addresses to IPv4 addresses and vice versa, facilitating seamless communication across different address families. References: Implementing and Operating Cisco Service Provider Network Core Technologies

SNMP Community String: Enable SNMP community string C1sc0 with read-only permissions.

Interface Index Persistence: Enable interface index persistence.

Restrict SNMP Community: Restrict the SNMP community to only the monitoring server with IP address 198.18.19.100/32.

View-Only Access: Provide view-only access to ospflfEntry and ospfNbrEntry.

When OSPF routers establish adjacency, they must agree on the MTU size on the connecting interface. If the MTUs do not match, the routers will not form an OSPF adjacency, and the link between them will not come up. Therefore, configuring the MTUs on the interfaces to match is essential for the OSPF network to function correctly.

When implementing a prefix list, it is a best practice to use nonsequential sequence numbers. This allows for the insertion of additional entries at a later time without the need to renumber the entire list, providing flexibility in managing the prefix list.

https://www.cisco.com/c/en/us/td/docs/ios/12_2sr/12_2sra/feature/guide/srtunsel.html#wp105781 5

The configuration for R1 indicates a BGP neighbor relationship with a device in AS 65012. However, R2 is actually in AS 65000, leading to a mismatch in AS numbers. This discrepancy will prevent the establishment of a BGP neighbor relationship between R1 and R2.

 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 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

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.

 The configuration shown is for the head-end router of a Cisco MPLS TE tunnel with segment routing. The commands included, such as “mpls traffic-eng tunnels” and “segment-routing mpls,” indicate that this is set up for a head-end router in an MPLS TE tunnel. There is no requirement for an explicit path or OSPF to be running, which eliminates options A and B. Option C is also incorrect as there’s no indication of a dynamic path configuration present.

OSPFv3 is used for routing IPv6 prefixes and requires that each interface intended to participate in OSPFv3 has the protocol enabled. This involves specifying the OSPF process ID and the area ID that the interface belongs to. The process ID links the interface to a specific OSPFv3 process running on the router, and the area ID determines the area within the OSPF topology that the interface is part of. Without this configuration, the interfaces will not actively participate in OSPFv3 route advertisement or neighbor relationships12.

References :=

Implementing and Operating Cisco Service Provider Network Core Technologies (SPCOR) course materials3.

Cisco OSPFv3 configuration guides and examples

 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 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.

https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/cether/configuration/xe-3s/asr903/16-12-1/b-ce-xe-16-12- asr900/m_ce_802_1ad_900.html

The mpls ldp graceful-restart command is applied in the global configuration mode in IOS XE Software. This command enables MPLS LDP Graceful Restart, which assists a neighboring router with MPLS LDP Stateful Switchover/Nonstop Forwarding (SSO/NSF) Support and Graceful Restart to recover gracefully from an interruption in service without losing its MPLS forwarding state1.

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 task requires the engineer to configure a route map that permits all unmatched routes during router redistribution within BGP. The correct action is to remove the implicit deny entry at the end of the route map, as indicated in Option C. By default, route maps have an implicit deny at the end, meaning that if a route doesn’t match any of the permit or deny statements in the route map, it will be denied. Removing this implicit deny entry ensures that all unmatched routes are permitted. References := Implementing and Operating Cisco Service Provider Network Core Technologies

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

 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.

IS-IS uses NET addresses to identify each router in the network, and the NET address of each router must be unique. In order for IS-IS to establish connectivity between R1 and R3, the NET address of R3 must be different from the NET address of R1, but it must also follow the same structure. In this case, the NET address of R1 is 49.0133.532b.ca14.6915.21311.F40F.1B3a.ba10.00, so the NET address of R3 must be 49.0133.532b.ca14.6915.21311.F40F.1B4a.bb87.00.

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.

A. Reconnect Timeout field: Specifies the time within which the LDP session should be reestablished after a failure.

C. Graceful restart capability in OPEN message: Indicates that the router supports LDP graceful restart and is capable of maintaining its MPLS forwarding state across a control plane failure.

D. Recovery Time field: Specifies the time that the router will maintain the MPLS forwarding state while it attempts to reestablish LDP sessions.

When choosing between SaltStack and Chef for network automation, it is important to consider that Chef is an agent-based tool written in Ruby, while SaltStack is a Python-based module tool. This fundamental difference in language and architecture can influence the decision based on the existing environment and the team’s expertise.

References :=

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

Official Cisco documentation and training resources available on the Cisco Learning Network Store.

 Router R1 is configured as a stub area with the “no-summary” option, which means it will not receive summary LSAs (Type 3) from the Area Border Router (ABR). It will only have Type 1 (Router LSAs) and Type 2 (Network LSAs) in its OSPF database for the area it belongs to. Router R2 is configured as an NSSA (Not So Stubby Area), which allows it to import AS external routes as Type-7 LSAs. These Type-7 LSAs can then be converted to Type-5 LSAs by the ABR when propagated into other areas. Therefore, R2 has Types 1, 2, and 7 LSAs in its OSPF database.