350-501 Sample Questions Answers

 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.

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

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

 The configuration in the exhibit shows the implementation of Nonstop Forwarding (NSF) with OSPF. NSF is used to minimize the downtime of neighbor relationships during a Route Processor (RP) switchover. The nsf command enables NSF, and ietf specifies the use of the IETF standard for graceful restart in OSPF. The restart interval 90 sets the time, in seconds, within which the restarting router should complete its restart, helping to maintain uninterrupted forwarding despite the switchover.

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

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

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

 In IS-IS, Level 2 peers must have matching authentication settings to ensure security and integrity of the routing domain. The hello timer setting must also match to ensure that the peers can maintain a consistent adjacency state. Mismatched hello timers could lead to adjacency flaps or failure to form an adjacency.

References: The information is based on the IS-IS protocol’s use of TLVs (Type-Length-Value) which makes it highly extensible. As new features come in, they can be added to the protocol with TLVs. This includes authentication mechanisms and timer settings that ensure secure and stable adjacencies between Level 2 peers

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

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

 The 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

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.

References: Implementing and Operating Cisco Service Provider Network Core Technologies (SPCOR) official course materials available on Cisco’s website.

The disruption in IS-IS connectivity between R1 and R2, despite the interfaces being up, suggests an issue with packet handling or MTU configuration. Action A, disabling padding for hello packets under the serial interface on R2, is necessary because excessive padding can lead to issues in processing hello packets effectively. Action C, changing the MTU to 1500 bytes on R2, addresses potential MTU mismatch issues. MTU mismatches are common problems that can interrupt connectivity in networks using routing protocols like IS-IS; ensuring both routers operate at the same MTU can resolve this issue.

References := The explanation is derived from the principles outlined in Cisco’s Implementing and Operating Cisco Service Provider Network Core Technologies, which emphasizes the importance of proper packet handling and MTU configuration for maintaining IS-IS connectivity.

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

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

NetFlow version 9 can report additional information such as BGP Autonomous System (AS) information due to its template-based design, which allows for flexibility and support for a wider range of IP flow information, including IPv4 and IPv6 flow information, BGP routing information, and multicast flow data.

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 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.

The correct configuration for extending the layer 2 domain between the company’s two locations involves setting up the interface with L2 transport, specifying the encapsulation method as dot1q with the VLAN tag of 12, and applying the appropriate rewrite ingress tag rules. This setup ensures that the VLAN tag is preserved across the service provider’s core, maintaining the layer 2 domain continuity.

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

In the context of VPLS (Virtual Private LAN Service) configuration, the engineer should perform additional configurations to enable the virtual switch instance. The correct answer is Option A, which likely involves configuring interface VLAN and associating it with xconnect vfi to establish end-to-end LAN connectivity between customer’s remote offices. This is essential for enabling VPLS, which allows geographically dispersed sites to be connected over a service provider’s network as if they were on the same local area network.

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

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

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

The 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

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

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

• 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.

 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

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

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

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

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

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

When a prefix list is applied to a BGP neighbor, it filters routes based on the specified conditions. In this scenario, the prefix list is designed to permit prefixes that are equal to or longer than /17 but shorter than or equal to /19. Therefore:

• A: 192.168.0.0/19 is denied because it falls outside the specified range.
• D: 192.168.0.0/16 is denied as it is shorter than the minimum length of /17.
• E: 192.168.0.0/16 is permitted because it is the exact prefix specified in the prefix list, and the ge and le modifiers apply to more specific routes derived from this prefix. References: Implementing and Operating Cisco Service Provider Network Core Technologies (SPCOR) - Cisco official courseware.

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

References:

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

In a multivendor network environment, it is essential to configure OSPF NSF with the IETF standard to ensure compatibility across different vendor devices. The command router ospf 1 nsf ietf enables OSPF NSF capability using the IETF standard, which facilitates uninterrupted forwarding during a route processor switchover.

References: Implementing and Operating Cisco Service Provider Network Core Technologies (SPCOR) - OSPF Nonstop Forwarding section.

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

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

The absence of routes learned by PE4 from PE5 in other PE routers’ routing tables is likely due to missing route target configurations. Route targets are crucial for importing and exporting VPN routes between VRFs in MPLS Layer 3 VPNs.

• Option D is correct because advertising the route targets for PE5 to the other PEs will allow them to import routes from PE5 into their respective VRFs, facilitating communication across the Layer 3 VPN.

References :=

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

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.

The command PE-A(config-pmap-c)#set dscp ef is used to apply DSCP marking to the traffic matched by the class-map. DSCP marking is a part of QoS policy to prioritize traffic. The ‘ef’ (Expedited Forwarding) value is commonly used for voice traffic to ensure it receives high priority and low delay through the network.

References: For more information, refer to the QoS section in the Implementing and Operating Cisco Service Provider Network Core Technologies (SPCOR) course materials.

In Cisco’s path selection process, the weight attribute is the first criterion for selecting a path. It is a Cisco-specific parameter, local to the router, and it is not propagated in routing updates. The path with the highest weight is preferred. Therefore, configuring a high weight on the peer to ASN 4567 will make Router R1 prefer this path for all outbound traffic directed towards ASN 4567. References: Implementing and Operating Cisco Service Provider Network Core Technologies (SPCOR) - Cisco SPCOR Training & Certification

 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 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.

References: For more detailed information, please refer to the Implementing and Operating Cisco Service Provider Network Core Technologies (SPCOR) course materials, specifically the sections covering MPLS and Layer 2 VPNs.

• References:

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

 Both Chef and Puppet are configuration management platforms that aim to configure and manage servers and other IT infrastructure. They operate in the same infrastructure management space and share several similarities:

• Use a master-client architecture: Chef functions with a master-client architecture, where the server runs on the master machine, and the client runs as an agent on every client machine. Similarly, Puppet follows a similar setup.
• Manage devices or nodes to be configured: Both Chef and Puppet manage the configuration of devices or nodes within an infrastructure.
• Leverage a pull model: Both tools use a pull model, where the configuration is pulled from a central server to the managed nodes.

https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/fnetflow/configuration/xe-3s/fnf-xe-3s-book/fnf-ipfix-expor t.html#d27853e197a1635

 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.

References: For more detailed information, please refer to the Implementing and Operating Cisco Service Provider Network Core Technologies (SPCOR) course materials, specifically the sections covering OSPF area types and LSA types.

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

The term ‘ImpNull’ in the CLI output indicates that Label 0, also known as the “Implicit Null” label, is used for the prefix displayed. This label instructs the penultimate router in an MPLS network to pop the label before forwarding the packet to the ultimate hop, which is the egress router. Therefore, Label 0 will not be part of the MPLS label stack for packets destined for 192.168.10.10 (Option A). This process is known as Penultimate Hop Popping (PHP) and is used to optimize the forwarding process by reducing one level of lookup at the egress router (Option D).

References: For more detailed information, please refer to the MPLS section in the Implementing and Operating Cisco Service Provider Network Core Technologies (SPCOR) course materials.

The OSPF neighbor relationship is not establishing due to a mismatch in MTU (Maximum Transmission Unit) settings on the interfaces of PE-A and PE-B routers. On PE-A, there is no MTU configuration under the interface FastEthernet0/0, which means it is using the default MTU setting. However, on PE-B, the MTU is explicitly set to 1400 bytes with “ip mtu 1400” command under interface FastEthernet0/0. OSPF requires that both ends of a point-to-point link have matching MTU sizes to form a neighbor relationship; otherwise, OSPF adjacency will not be established.

References:

• Implementing and Operating Cisco Service Provider Network Core Technologies (SPCOR) - Cisco SPCOR Resources

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

 In Cisco Service Provider Network Core Technologies, an EVPN instance can be likened to a VRF (Virtual Routing and Forwarding). A VRF allows multiple instances of a routing table to co-exist within the same router at the same time. Similarly, EVPN provides separation between routing instances which aligns with how VRF operates.

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

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.

Solution

R3

router bgp 65413

add ipv4

nei 2.2.2.2 allowas-in

nei 4.4.4.4 allowas-in

add ipv6

nei 2001:db8:4:4:4::4 allowas-in

end

copy run start

=======================

R2

router bgp 65413

nei 1.1.1.1 as-override

nei 3.3.3.3 as-override

end

copy run start

=======================

R3

router bgp 65413

nei 10.3.4.2 remot 65412

nei 2001:db8:3:4::2 remot 65412

nei 2001:db8:4:4:4:4::4 remot 65412

nei 2001:db8:4:4:4:4::4 ebgp-multihop 10

add ip4

nei 10.3.4.2 act

ex

add ipv6

nei 2001:db8:4:4:4:4::4 activate

nei 2001:db8:4:4:4:4::4 ebgp-multihop 10

nei 2001:db8:3:4::2 act

end

copy run start

===================

R4

router bgp 65412

nei 10.3.4.1 remot 65413

nei 2001:db8:3:3:3:3::3 remot 65413

nei 2001:db8:3:3:3:3::3 ebgp-multihop 10

nei 2001:db8:3:4::1 remot 65413

add ipv4

nei 10.3.4.1 remot act

nei 10.3.4.1 prefix-limit 10

add ipv6

nei 2001:db8:3:3:3:3::3 activate

nei 2001:db8:3:3:3:3::3 ebgp-multihop 10

nei 2001:db8:3:3:3:3::3 prefix-limit 10

nei 2001:db8:3:4::1 activate

nei 2001:db8:3:4::1 prefix-limit 10

end

copy run start

 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 regular expressions, the caret (^) is used to indicate the start of a string. This is a fundamental concept in pattern matching using regular expressions, where ^ matches the position at the beginning of the string.

References: This information is consistent with regular expression syntax as described in various Cisco documentation and resources related to Cisco IOS software configurations.

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

The QoS-group keyword on Cisco IOS XR is used for marking packets on the ingress of the device. This allows for internal handling and is not transmitted across the network. It can be used in fabric QoS policy as a match criteria to apply specific policies based on the QoS group marking.

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

•  By setting IP precedence values (using Differentiated Services Code Point - DSCP) and configuring traffic policing, the network can enforce policies to drop or mark packets based on their priority. When traffic exceeds the specified threshold, the network can take appropriate actions.
• References: Implementing and Operating Cisco Service Provider Network Core Technologies (SPCOR) v1.0

 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

The correct command to authenticate the OSPF neighbor between PE-A and PE-B using MD5 is found in Option A. In this option, the command ip ospf message-digest-key 1 md5 44578611 is used to configure OSPF MD5 authentication on an interface with the key ID as 1 and key string as 44578611. The second command ip ospf authentication key-chain 44578611 is used to enable OSPF authentication on an interface and associate it with a specific key chain. References := Cisco - Implementing and Operating Cisco Service Provider Network Core Technologies

 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

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.

References: Implementing and Operating Cisco Service Provider Network Core Technologies (SPCOR v1.0); Cisco official documentation on BGP Configuration.

In this scenario, when edge routers at different regional sites are connected over a global carrier backbone, MP-eBGP must be run between routers to exchange customer VPNv4 routes. This is essential for enabling communication between customer sites located in different regions while utilizing a global carrier backbone service. References: Implementing and Operating Cisco Service Provider Network Core Technologies source documents or study guide

The configuration shown indicates that Router 1 is set up with a route-map named “ddos” that matches traffic tagged with “tag 1”. The traffic matching this tag is then set to have a next-hop IP of 192.0.2.1 and a local preference of 150. The community is also set to “no export”, which means this route will not be advertised to external BGP peers. Since there’s no explicit deny statement in the configuration, only traffic with tag 1 and local preference of 150 will be dropped by Router 1 as per the BGP routing policy. References: Implementing and Operating Cisco Service Provider Network Core Technologies course materials. 

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

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

Cisco MPLS TE uses OSPF extensions to allow for optimized transit between a headend router and a destination router by utilizing Opaque LSAs. Opaque LSAs allow for the calculation and establishment of unidirectional tunnels that are set according to the network constraint. The tunnels are built bidirectionally by utilizing Router LSAs, which share router link advertisements to each router within the MPLS environment. ASBR Summary LSAs are also used to share OSPF domain information so that the two routers know how to reach each other during tunnel setup. Furthermore, Network LSAs are used to share RSVP information which is necessary for setting up the tunnel between the two routers.

 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. 

 The show isis neighbors command is used to display the Intermediate System to Intermediate System (IS-IS) neighbors that the router has discovered. This command is essential for troubleshooting and verifying the IS-IS network’s topology and ensuring that the router has formed the correct adjacencies with its neighbors.

References := For more detailed information and study materials, you can refer to the official Cisco course page for “Implementing and Operating Cisco Service Provider Network Core Technologies” here and the on-demand e-learning resources here.

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.

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

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

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

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

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

 In BGP, the Local Preference attribute is used to influence the exit point from an AS (Autonomous System). A higher local preference value is preferred, and all routes received inherit the local preference value of the route that is installed in the IP routing table. So, configuring a higher local preference outbound will make specific BGP speakers as preferred exit points for customer AS. References := Cisco

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

 To align with customer contract SLAs and allow 10% of interface capacity on router R3 for traffic from CE1 towards the FTP server, the network engineer must apply a policy map to R1 to reserve the remaining 10% of interface bandwidth (Option C). Additionally, applying a policy map to R3 to reserve 10% of interface bandwidth (Option D) ensures adherence to the customer’s contract SLAs while utilizing the allocated bandwidth capacity. References: Implementing and Operating Cisco Service Provider Network Core Technologies (SPCOR) - Quality of Service section.

RSVP (Resource Reservation Protocol) is used with MPLS (Multiprotocol Label Switching) traffic engineering tunnels primarily to reserve bandwidth along the path of the tunnel. This ensures that sufficient resources are allocated for the traffic to meet quality of service requirements, which is crucial for maintaining the performance of critical applications that traverse the network. References := For more information on RSVP and MPLS traffic engineering, refer to the Implementing and Operating Cisco Service Provider Network Core Technologies (SPCOR) course materials, which provide detailed explanations on how these technologies work together to optimize network traffic1.

Here is the solution:

Text Description automatically generated

 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.

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

TASK1:Run “sh run” command on both routers, check if there is any “router ospf” configured. If it’s configured, check if Loopback0 ip it’s being used as OSPF ID. If it’s, jump to TASK2. Otherwise run:R1

router ospf 10

router-id 10.1.1.1

R2

router ospf 10

router-id 10.2.2.2

TASK2:

R1 & R2

int lo0

ip ospf 10 area 0

ip ospf network point-to-point

!

int e0/0

ip ospf network point-to-point

ip ospf 10 area 0

ip ospf authentication message-digest

ip ospf message-digest-key 1 md5 C1sc0!

!

 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.

Remember that SSM is an extension of IP multicast where datagram traffic is forwarded only from explicitly joined multicast sources to receivers. It creates source-specific multicast distribution trees without shared trees.

References:

• Cisco PIM-SSM Configuration Example
• Cisco IP Multicast: PIM Configuration Guide

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

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

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. 

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

• PE-2 should import the OSPF route from the global routing table into the CUSTOMER-ABC VRF. This allows the VRF to have internet reachability.
• The configuration should include an import route-target statement under the VRF configuration on PE-2. The route target should match the one used by CE-1 to advertise the default route (0.0.0.0/0) to PE-1.

References:

• Implementing and Operating Cisco Service Provider Network Core Technologies (SPCOR) study guide or official documentation.

 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

TI-LFA, or Topology Independent Loop-Free Alternate, is a fast-reroute mechanism that provides protection against link or node failures in a network. It guarantees a loop-free alternate path for all areas configured in OSPF, ensuring traffic can be quickly rerouted in case of a failure. This characteristic is crucial for maintaining network stability and avoiding traffic loops, which can lead to packet loss and network congestion.

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

• Cisco MPLS TE tunnels can be established using IS-IS and OSPF as the routing protocols. These protocols allow the creation of traffic-engineered paths within the MPLS network.
• References: Implementing and Operating Cisco Service Provider Network Core Technologies course materials.

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

 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.

References:

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

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

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.

References: Cisco Community, Cisco Documentation

Router 4 must be in the same area as Router 1, so it should have the same area address which is “49.0111”. The system ID can be different to uniquely identify the router in that area, but since there is no option with a different system ID and the same area address, option B is correct as it has both the same area address and system ID as Router 1. References := Cisco

 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