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

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.

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

 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.

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.

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

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

The configuration in Option A is correct for enabling dial-out telemetry streams using gRPC on devices with TLS disabled.

It uses model-driven telemetry (MDT), which is a new method of monitoring network devices. Unlike traditional methods that pull data from the device, MDT pushes data from the device to the collector.

In this configuration:

Telemetry is model-driven.

It specifies a destination group with an IP address and port number where the telemetry data will be sent.

The encoding is self-describing-gpb (Google Protocol Buffers).

The protocol used is TCP.

This setup ensures that telemetry data is sent to the specified collector without requiring TLS encryption.

https://www.cisco.com/c/en/us/solutions/service-provider/mobile-internet/5g-transport/converged-5g-xhaul-transport.html#

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

The configuration snippet in the exhibit shows that BGP summarization is configured with the “aggregate-address” command followed by an IP address and a subnet mask, and then the “summary-only” and “as-set” options. The IP address is 192.168.0.0, and the subnet mask is 255.255.0.0, which corresponds to a /16 prefix length (indicating that the first 16 bits of the IP address are the network portion). However, there seems to be a typo in option B as it’s not a valid IP address format; hence option A is correct with an assumption of typo error.

The configuration ip verify unicast source reachable-via any under interface gigabitethernet0/1 on Router 1 ensures that incoming packets have a source IP address that matches an entry in the FIB (Forwarding Information Base), indicating it’s reachable via a real interface. This helps mitigate attacks by dropping traffic with unreachable source addresses. References := Cisco

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

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.

 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.

The issue of no LDP neighbor existing for 1.1.1.1 between two directly connected routers could be due to R2 not receiving any hellos from R1. In the context of LDP (Label Distribution Protocol), hellos are used for the discovery of LDP peers. They are sent periodically on each interface that LDP is enabled on to discover and maintain LDP sessions with neighbors. If R2 is not seeing any hellos from R1, it means there’s a failure in the initial step of establishing an LDP session, hence no neighbor relationship is formed.

 The show command output indicates that the BGP neighbor is in an Idle state, which means the BGP session has not been established. Additionally, it mentions “eBGP neighbor with no inbound or outbound policy; defaults to ‘drop’”. This implies that in the absence of specific policies for route advertisement and acceptance, the default action is to drop all routes. Therefore, no routes are accepted from the neighbor 192.168.2.2, nor are any routes advertised to it, aligning with option C. References: = Implementing and Operating Cisco Service Provider Network Core Technologies course materials.

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

 The control plane protocol used between Cisco SD-WAN routers and vSmart controllers is the Overlay Management Protocol (OMP). OMP is a proprietary protocol of Cisco SD-WAN that facilitates the exchange of routing, policy, and management information across the network. It operates within the secure environment provided by the Datagram Transport Layer Security (DTLS) or Transport Layer Security (TLS) control connection, ensuring that the communication between the routers and controllers is encrypted and authenticated1.

References := Cisco 300-415: Cisco SD-WAN vSmart-WAN Edge Router Control Plane Protocol

 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.

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.

 QPPB (QoS Policy Propagation via BGP) is a mechanism that allows the application of QoS policies using IP precedence or QoS group settings based on BGP community lists, AS paths, and prefix lists. In the context of the exhibit provided, it’s clear that QPPB is being used to apply a specific QoS policy (qos-group 10) based on AS path attributes. This aligns with option C, as it indicates that QoS policies are utilizing BGP to achieve comprehensive network coverage.

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

The correct 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.

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.

Here is the solution:

The issue described indicates that the preferred BGP path for traffic destined to 192.168.1.1/32 is not being used. By applying a route-map with a higher Local Preference (LP) on R1 for the prefix 192.168.1.1/32, the BGP path attributes can be manipulated to prefer the path through R2. Local Preference is a BGP attribute that determines the preferred exit path out of an AS. A higher Local Preference value is preferred over a lower one. Therefore, configuring the route-map High-LP with a higher Local Preference on R1’s BGP peering with R2 will influence the BGP path selection process, ensuring that traffic for 192.168.1.1/32 prefers the path R3-R2-R1 as expected.

The issue with Router 1 missing the route for Router 2’s loopback 0 is likely due to the routers being configured in different OSPF areas. For OSPF to properly exchange routing information, routers within the same network should be configured in the same area. Therefore, the engineer should change the area numbers on Router 1 and Router 2 to be the same, ensuring they can exchange routes, including the route for Router 2’s loopback 0.

Best – 50.50.50.2

2nd Best – 40.40.40.2

3rd Best – 20.20.20.2

44th Best – 30.30.30.2

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

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

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

 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

IOS XE:

It uses linux-based kernel

It has a separate control plane

IOS:

It is monolithic

It shares memory space

PCE – 1,2,5

PCC- 3,4

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

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

 To configure extended discovery to support the MPLS LDP session between the headend and tailend routers, the engineer must configure a targeted neighbor session. This action allows for the establishment of LDP sessions between routers that are not directly connected, which is necessary for setting up MPLS tunnels that span multiple hops in the network.

References := The concept of targeted LDP sessions is covered in the Implementing and Operating Cisco Service Provider Network Core Technologies (SPCOR) curriculum, which explains how these sessions are used to establish LDP relationships over a non-directly connected interface, facilitating MPLS tunneling for applications like video streaming.

When implementing traffic shaping on a network, the goal is to control the rate of traffic being sent into the network to avoid congestion. This is done by buffering excess packets and then scheduling them to be sent out at a steady rate.

Option A is correct because traffic shaping requires a queue with sufficient memory to buffer excess packets. When the traffic rate exceeds the configured maximum rate (shaping rate), the excess packets are temporarily stored in the queue until they can be sent out, ensuring a smooth flow of traffic without overwhelming the network1.

Option B is also correct as traffic shaping involves configuring token values in bytes. Tokens are used to represent permission to send a certain amount of data. The token bucket is filled with tokens at a steady rate, and packets can only be sent if there are enough tokens in the bucket. The token values determine the size of the bucket and the rate at which it is refilled, which in turn controls the rate of traffic1.

Option C is incorrect because packet remarking for excess traffic is not a component of traffic shaping. Packet remarking is typically used in conjunction with policing, where packets that exceed the rate limit can be remarked to a lower priority for downstream handling1.

Option D is incorrect in the context of traffic shaping. While a scheduling function is used to handle the packets that are delayed due to buffering, the scheduling itself is not part of the shaping mechanism but rather a function of the queuing system that works alongside shaping1.

Option E is incorrect as it pertains to traffic policing, not shaping. In traffic policing, packets that exceed a certain threshold are discarded or remarked, whereas shaping delays excess packets by buffering them1.

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

 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.

 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.

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

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

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.

Here is the solution:

To mitigate DDoS attacks in a BGP environment, an engineer can apply BGP FlowSpec, which allows for the creation of traffic filtering policies that can be distributed across the network. This configuration enables the network to respond quickly to DDoS attacks by filtering or redirecting malicious traffic based on predefined criteria, such as source IP, destination IP, and port numbers456.

 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. 

 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

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.

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.

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

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

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

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

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

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

The correct configuration for deploying VRF on ASBR router R1 to have connectivity over an MPLS VPN inter-AS Option AB network is found in option C. This involves configuring the interface with the commands shown, including setting the interface ethernet, applying IP VRF forwarding, and enabling MPLS BGP forwarding. These steps ensure that the interface is properly configured for VRF and can support MPLS VPN inter-AS communications effectively. References := Implementing and Operating Cisco Service Provider Network Core Technologies

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

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.

 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.

 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.

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

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.

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

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

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

A. 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 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.

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

 The requirement is for R2 to delay sending BGP updates to R5 for multicast traffic by 30 seconds. This can be achieved by configuring the advertisement interval for IPv4 multicast traffic on R2, which controls the frequency of sending BGP updates for multicast routes. References := Cisco SPCOR

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

 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.

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

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

The configuration snippet shows that MPLS and LDP are configured globally but not enabled on an interface. The commands include “mpls label protocol ldp,” “mpls ldp router-id loopback 0,” and “mpls ip,” which are necessary for global settings. However, to establish LDP neighbors and exchange labels, LDP must be enabled on the specific interface where it’s needed.

 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.

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

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

To redirect traffic from ASN 64501 to 10.0.0.0/8 via the primary link North_A instead of the slow backup link North_B, setting a higher local preference between North_A and South_A is required. Local preference is a BGP attribute that helps in selecting the exit point from an AS (Autonomous System). By increasing local preference for routes received on North_A, traffic will be directed through this path as it becomes more preferred. References := Cisco Implementing and Operating Cisco Service Provider Network Core Technologies (SPCOR)

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

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

The 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

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.

 The configuration shown in the exhibit indicates a BGP FlowSpec policy that is configured locally on CSR1. This policy is designed to drop all traffic destined for TCP ports 80 and 443 for the IP address 10.6.5.0/24. The traffic rate is displayed as 0 bps, which suggests that the policy is not currently dropping any traffic. However, the matched and dropped statistics indicate that the policy has been active in the past, as it has matched and dropped packets.

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

Area 10 should receive inter-area routes and support mutual redistribution with the extranet but not receive the default route (::/0). This requirement does not align with any of the stub or NSSA configurations, as these would restrict the type of routes received.

Area 11 should only receive the default route from the ABR and not support external route redistribution or advertise inter-area routes. Configuring Area 11 as an NSSA (Not So Stubby Area) with the no-summary option on R7 and as NSSA on XR31 would prevent inter-area routes from being advertised into Area 11. Additionally, the default-information-originate command on R7 would generate a default route into Area 11, fulfilling the requirement.

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

 The ttl-security hops  command sets the maximum number of hops that a BGP message can traverse. In this case, setting ttl-security hops 2 means that the router will accept BGP packets from a neighbor (2.2.2.2) only if the TTL is 253 or more. This is because the default TTL value is 255, and for each hop, the TTL is decremented by 1. Therefore, a packet from a directly connected neighbor would have a TTL of 254 when it reaches the PE router. If the packet has traversed one more router (making it two hops away), the TTL would be 253 upon arrival.

The BGPsec framework is designed to secure the AS path information in BGP updates. It uses digital signatures to validate the AS path and prevent unauthorized route manipulation. Here are the key points related to BGPsec:

Securing AS Path:

BGPsec ensures the integrity of the AS path by allowing routers to sign BGP updates using their private keys.

When a router originates a BGP route, it signs the AS path information with its private key.

Other routers can verify the signature using the corresponding public key.

This prevents malicious AS path modifications and ensures the authenticity of the advertised route.

Private Keys and Router Key Pair:

BGPsec relies on cryptographic keys for signing and verifying BGP updates.

Each router has a router key pair consisting of a private key and a corresponding public key.

The private key is kept confidential and is used for signing route updates.

The public key is distributed to other routers for verification.

Expiration Time:

Unlike regular BGP updates, BGPsec does not assign an expiration time (TTL) to route advertisements.

The absence of an expiration time ensures that the signed AS path remains valid until explicitly withdrawn.

In summary, BGPsec enhances BGP security by securing the AS path using digital signatures and private keys. It does not rely on IPsec tunnels for security1.

 Enabling MPLS LDP IGP Synchronization ensures that the IGP advertises a route only if there is a corresponding label binding from LDP. This synchronization helps prevent blackholing traffic when there is a direct link failure in the network. When the B-C link failed, the IGP could find an alternate path via routers E and F, but without LDP synchronization, the labels for MPLS were not available on this new path, leading to traffic loss. By enabling LDP IGP Synchronization, routers will only use paths for which a complete set of labels exists, ensuring label forwarding occurs on the alternate path.

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.