Free Practice Questions for the Cisco CCNP Service Provider 350-501 Exam (2026 Updated)

The Internet gateway router being connected as a PE router to the MPLS backbone is a design attribute that can be used to provide Internet access to a major customer through a separate dedicated VPN. This setup allows for efficient routing and separation of traffic, ensuring security and performance.

The command  channel-group 1 mode desirable  configures the switch port to actively send PAgP packets to negotiate forming an EtherChannel. PAgP is a Cisco-proprietary protocol used in the automatic creation of EtherChannel links. When set to ‘desirable’, the port actively attempts to form an EtherChannel, which means it sends PAgP packets without waiting for the connected peer to initiate the negotiation.

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.

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

 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.

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

QoS-aware tunneling : Unfortunately, Cisco MPLS TE tunnels do not inherently support Quality of Service (QoS) awareness. This means that the tunnels themselves do not directly consider QoS parameters when making routing decisions. QoS policies must be applied separately at the network level, and the TE tunnels do not inherently take QoS into account during path selection.

Tunnels spanning multiple OSPF areas : Contrary to option A, Cisco MPLS TE tunnels can indeed span multiple OSPF areas. The use of OSPF areas does not inherently restrict the creation of MPLS TE tunnels across area boundaries.

ISIS metrics : Option B is incorrect. When using ISIS (Intermediate System to Intermediate System) as the Interior Gateway Protocol (IGP), newer-style metrics (such as wide metrics) are supported. Older-style metrics are not the only option.

Tunnels over IP unnumbered links : Option C is also incorrect. Cisco MPLS TE tunnels can be configured over IP unnumbered links, allowing efficient use of IP addresses.

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

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.

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

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).

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

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

Option A  corresponds to the desired configuration. It uses an  access-list  to permit IGMP joins for the specific multicast group  239.10.10.10  from the source  172.20.20.3 .

Options B, C, and D  do not match the desired configuration. They either allow all IGMP traffic or do not specify the correct source and group addresses.

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

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

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

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

References

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

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 reliability 1 2 3 .

In the context of OSPF multiarea implementation, adjacency issues can often be resolved by specifying the type of network on the interface. In this case, option B “ip ospf network point-to-point” is appropriate as it helps in forming OSPF adjacency over point-to-point links by allowing OSPF to use a simpler neighbor discovery process, which can resolve adjacency issues.  References  :=  Implementing and Operating Cisco Service Provider Network Core Technologies

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.

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 network 1 .

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 traffic 1 .

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 handling 1 .

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 shaping 1 .

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 them 1 .

 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.

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.

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

To 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.

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.

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.

 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.

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.

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

 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 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.

Cisco Internetwork Operating System (IOS) is the software used on most Cisco Systems routers and current Cisco network switches. IOS is a package of routing, switching, internetworking and telecommunications functions integrated into a multitasking operating system. IOS uses a monolithic architecture, meaning that all processes run in a single address space, making it a single-image system.

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.

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.

 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 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,  < bgpPeerP addr= " 192.168.1.2 " >  specifies the neighbor’s IP address, and  < bgpAsP asn= " 65514 " / >  indicates the AS number of the neighbor.

Path Computation Element (Calculates paths through the network, keeps TE topology database information, sends path status updates)

Path computation Client (sends path calculation request, sends path creation request)

Path Computation Element (PCE)

Represents a software module (which can be a component or application) that enables the router to compute paths applying a set of constraints between any pair of nodes within the router’s TE topology database. PCEs are discovered through IGP.

Path Computation Client (PCC)

Represents a software module running on a router that is capable of sending and receiving path computation requests and responses to and from PCEs. The PCC is typically an LSR (Label Switching Router).

https://www.cisco.com/c/en/us/td/docs/routers/crs/softwa re/crs_r5-3/mpls/configuration/guide/b-mpls-cg53x-crs/b-mpls-cg53x-crs_chap ter_0110.html#con_1279822

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.

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 .

 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

Here is the solution:

To implement Bidirectional Forwarding Detection (BFD) in an IS-IS environment, the first task is to configure BFD in an interface configuration mode. This involves setting up BFD parameters on the interfaces where IS-IS is running to enable quick failure detection.

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 configurations 4 5 6 .

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 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.

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.

When implementing LDP NSF (Nonstop Forwarding) on the network, an engineer must perform the following tasks:

Implement direct connections for LDP peers : This ensures that LDP sessions can be reestablished quickly after a switchover.

Enable NSF for the link-state routing protocol in use on the network : This allows the routing protocol to maintain its state during a switchover, ensuring seamless operation.

For example, if OSPF is the link-state routing protocol, enabling NSF for OSPF ensures that OSPF adjacencies are maintained during a switchover

For encrypted authentication on Router 1, the correct action is to configure an SNMP user with an authentication password and associate it with a group. Option B includes the use of MD5 authentication, which provides the required security for message confidentiality.

 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

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

 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.

 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. 

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

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

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.

 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.

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.

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.

 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.

R1

R2

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

References  := The information is based on the Implementing and Operating Cisco Service Provider Network Core Technologies (SPCOR) training and certification resources, which offer a deep dive into service provider technologies, including core architecture, services, networking, automation, quality of services, security, and network assurance 1 2 3 .

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

To establish LDP sessions between the PE and P routers, you need to enable communication over TCP port 646 for T-LDP hello messages.

T-LDP (Targeted LDP) uses TCP port 646 for session establishment.

Example configuration:

interface GigabitEthernet0/0

mpls ldp discovery targeted-hello accept

 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.

 The  ttl-security hops < number >  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.

 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.

 In XML, a self-closing tag such as  < tag/ >  indicates that the element does not contain any data, hence the data field is considered blank. This is a common way to represent empty elements in XML documents.

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.

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.

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 relationships 1 2 .

References  :=

Implementing and Operating Cisco Service Provider Network Core Technologies (SPCOR) course materials 3 .

Cisco OSPFv3 configuration guides and examples

R1

key chain AUTH_ISIS

key 2

key-string C1sco!

exit

int range et0/0 , et1/0

isis authen key-chain AUTH_ISIS

ip isis

isis metric 15

Copy run start

R2

key chain AUTH_ISIS

key 2

key-string C1sco!

exit

int range et0/0 , et1/0

isis authen key-chain AUTH_ISIS

ip isis

isis metric 20

Copy run start

R3

key chain AUTH_ISIS

key 2

key-string C1sco!

exit

int range et0/0 , et1/0

isis authen key-chain AUTH_ISIS

ip isis

isis metric 25

Copy run start

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

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

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

The 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”.

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

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.

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

 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.

In an MPLS network, the Label Distribution Protocol (LDP) is used to distribute labels which can include segment prefixes. LDP is a protocol that automatically generates and exchanges labels between routers, allowing for the forwarding of packets along a predetermined path without the need for complex lookups in a routing table at every hop.

 To achieve this, we need to apply an  access control list (ACL)  on  PE-R9  that permits  SSH  traffic from the  management network 192.168.0.0/16  while denying other traffic. The correct ACL configuration is as follows:

access-list 100 permit tcp 192.168.0.0 0.0.255.255 any eq 22

access-list 100 deny ip any any

The first line permits  TCP traffic  from the  management network  to any destination with  destination port 22  (SSH).

The second line denies all other IP traffic.

In MPLS Layer 3 VPNs, shared services such as Internet access can be provided through the use of a shared services VRF (Virtual Routing and Forwarding). The customer VRF uses route targets to import routes from the shared services VRF, which contains the routes to the Internet. This allows the customer sites to access the Internet without compromising the isolation of their private networks.  References : The concept of shared services VRF and the use of route targets for importing and exporting routes are common practices in MPLS VPN implementations.

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 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.

 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.

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 I nformation Base), indicating it’s reachable via a real interface. This helps mitigate attacks by dropping traffic with unreachable source addresses.  References  :=  Cisco

OSPF adjacency is established when two OSPF routers have matching interface parameters. This includes the OSPF router ID, network address, area ID, and other OSPF-specific configurations such as MTU size and network type. For example, the configuration commands provided in the image description suggest setting the OSPF router ID, network address with a wildcard mask, and specifying the OSPF area. Additionally, the interface is set to a point-to-point network type with a specific MTU size, which is important for OSPF adjacency as mismatched MTU sizes can prevent OSPF neighbors from forming an adjacency.

: In the context of telemetry for data analytics, a destination (such as a collector or monitoring system) initiates a session to a router. This session allows the router to send telemetry data to the destination for analysis.

When there is an LSP breakage during the testing of MPLS OAM ping capabilities, the ingress MPLS router does not receive any reply because MPLS OAM ping is used to verify connectivity over Label Switched Paths (LSPs), and if an LSP is broken, the echo request will not reach the egress router, resulting in no echo reply being sent back.

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 < VRF-NAME > 0.0.0.0 0.0.0.0 < NEXT-HOP >  command.

Redistribute the static route  into BGP using the  redistribute static  command under the BGP VRF configuration.

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

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

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

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.

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.

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.

 To meet the scalability and service recovery requirements, the network engineer should implement BGP PIC core functionality on routers R2 and R3 (Option A). This will enhance the convergence time during a failure. Additionally, establishing BGP connectivity between routers R1 and R4 with VPNv4 address family enabled (Option C) will facilitate MPLS services across multiple IGP domains.

References  :=

Implementing and Operating Cisco Service Provider Network Core Technologies

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

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

 The 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