In a hub-and-spoke VPRN topology, two distinct Route Targets (RTs) are used to control route distribution. The hub PE exports its routes with one RT (the "hub" RT) and imports routes tagged with a different RT (the "spoke" RT). Conversely, all spoke PEs import the "hub" RT and export the "spoke" RT.

In this scenario, target:65100:1 acts as the "hub" RT, and target:65100:2 acts as the "spoke" RT. The command export target:65100:1 import target:65100:2 is configured on the hub PE (PE1) to advertise its routes to all spokes and accept routes from all spokes, establishing the required hub-and-spoke connectivity.

B. PE2, PE3 and PE4 are spoke PEs. They would be configured with the inverse RT policy (export target:65100:2 import target:65100:1) to communicate only with the hub.

C. Configuring this command on all PEs would not create the desired hub-and-spoke topology, as spokes would incorrectly export the hub RT.

D. This route target command structure is the fundamental mechanism for creating a hub-and-spoke VPRN and is therefore essential for the configuration.

1. Nokia 7750 SR OS Services Guide, Release 22.10.R1, "VPRN services" chapter, Section: "Hub and Spoke VPRN Topologies": This section explicitly describes the use of separate import and export route targets for hub and spoke sites. It states, "The hub site is configured to export its routes with a specific route target and import routes from all spoke sites... The spoke sites are configured to import the hub’s routes and export their routes to the hub site." This directly supports the configuration logic applied to PE1.

2. Nokia 4A0-106 Courseware, "Nokia Virtual Private Routed Networks Student Guide", Module 3: VPRN Service Implementation: The course material details VPRN topologies, including hub-and-spoke. Configuration examples show the hub PE exporting one RT and importing another, while spoke PEs have the reverse configuration, confirming the command in the question is for the hub PE.

In a VPRN (MPLS L3VPN), Multi-Protocol BGP (MP-BGP) is used to distribute customer VPN routes across the provider's core network. These routes are exchanged between Provider Edge (PE) routers as VPN-IPv4 prefixes. To ensure that all PEs participating in a VPRN learn the routes from all other PEs in the same VPRN, a logical full mesh of internal BGP (iBGP) sessions is required between them. This allows a route learned from a Customer Edge (CE) device at one PE to be advertised to all other remote PEs, providing full connectivity for the customer's sites. While route reflectors can be used to simplify the physical configuration, the logical topology remains a full mesh where every PE can exchange routes with every other PE.

A. Full mesh between all CE, PE and P devices: P (Provider) routers are typically not BGP-aware and do not participate in VPRN routing; they only perform label switching. CEs do not peer with P routers.

B. Full mesh between PE and P devices: P routers do not run BGP for VPRN services. BGP sessions for route distribution are established between PE routers, not with P routers.

C. Full mesh of P devices: P routers are part of the transport core and are not involved in BGP peering for VPRN route exchange.

E. Full mesh between PE and CE devices: A CE device only needs a BGP session with its directly connected PE(s). There is no requirement for a full mesh between all CEs and all PEs.

1. Nokia 7750 SR OS Services Guide, Release 21.10.R1: In the "VPRN Service Overview" section, under "Distributing VPN-IPv4 Addresses", the documentation states: "To distribute VPN routing information across the service provider's network, PE routers must be configured to establish BGP sessions with other PE routers. A full mesh of iBGP sessions must be established between all PE routers, or a route reflector must be used." (Document ID: 3HE 17194 AAAC TQZZA, Section: VPRN Service Overview). This directly confirms the requirement for a full mesh of PE devices.

2. Rosen, E., & Rekhter, Y. (2006). BGP/MPLS IP Virtual Private Networks (VPNs). RFC 4364. Section 4, "Distributing VPN-IPv4 Information", describes the BGP mechanisms. It states, "If a set of PEs are in the same AS, they may be fully meshed, or they may use BGP route reflectors to distribute VPN-IPv4 routes." This foundational IETF standard establishes the logical full-mesh requirement (or its RR-based equivalent) between PEs in the same Autonomous System. (Available at: https://doi.org/10.17487/RFC4364)

A Layer 3 VPN provides routed, IP-based connectivity to customers across a provider's shared backbone. The term IP-VPN is a generic industry name for this service. The most prevalent technology for implementing this is BGP/MPLS VPN, as standardized in IETF RFC 4364, which uses Multiprotocol BGP to distribute customer routes. VPRN (Virtual Private Routed Network) is the specific term used by Nokia to describe its Layer 3 VPN service implementation on its Service Router platforms. All three terms correctly describe a Layer 3 VPN service from different perspectives (generic, technological, and vendor-specific).

C. VLL: Virtual Leased Line (VLL) is a point-to-point Layer 2 VPN service that emulates a private line, not a routed Layer 3 network.

D. VPLS: Virtual Private LAN Service (VPLS) is a multipoint Layer 2 VPN service that emulates an Ethernet LAN segment across a WAN.

F. ePipe: This is Nokia's specific product name for a point-to-point Ethernet VLL (a Layer 2 service), not a Layer 3 VPN.

1. Nokia 7750 SR OS Services Guide, Release 21.10.R1: In the "VPRN Services" chapter, the introduction states, "A Virtual Private Routed Network (VPRN) is a Layer 3 virtual private network (VPN) service that consists of a set of customer sites connected to a common IP/MPLS service provider network." This directly links VPRN to Layer 3 VPNs. The same guide defines VPLS and ePipe services as Layer 2 VPNs in their respective chapters.

2. Rosen, E., & Rekhter, Y. (2006). BGP/MPLS IP Virtual Private Networks (VPNs). RFC 4364. Internet Engineering Task Force (IETF). The title and abstract of this foundational document explicitly define the "BGP/MPLS IP VPN" architecture. The abstract states, "This document describes a method by which a Service Provider may use an IP backbone to provide IP Virtual Private Networks (VPNs) for its customers." This confirms that BGP/MPLS VPN and IP-VPN refer to the same Layer 3 service. (DOI: https://doi.org/10.17487/RFC4364)

The BGP AS path 65100 65100 is a distinctive indicator of the as-override feature in operation. This feature is typically used by a service provider to connect two or more customer sites that share the same Autonomous System (AS) number. When the provider's router (in AS 65100) advertises a prefix from one customer site to another, it replaces the customer's AS number in the path with its own AS number (65100) to avoid the BGP loop prevention mechanism. The receiving customer router then sees the path as originating from the provider, with the provider's AS listed twice. This indicates the prefix originated from another site connected via the single provider AS, 65100.

A. A prefix in a directly connected AS would have an AS path length of one (e.g., 65100), not two.

C. Two Autonomous Systems between the local and originating AS would result in an AS path length of at least three (e.g., AS1 AS2 OriginAS).

D. The AS path X X is the classic and most direct result of as-override across a single transit AS, making it the most likely scenario, not one with two or more.

E. AS 65100 is the transit (provider) AS. The as-override feature masks the true originating AS, but the prefix itself is located at the other customer site, not within the provider's network.

1. Nokia 7750 SR OS Services Guide, Release 21.10.R1, VPRN Services Guide. In the "VPRN BGP" chapter, the section on "BGP AS Override" states: "The as-override command replaces the AS number of the originator with the AS number of the provider edge (PE) router. This is used in cases where a customer is using the same AS number at different sites... When as-override is enabled, the PE router replaces the AS number of the CE with its own AS number in the AS path." This process creates the observed [ProviderAS ProviderAS] path, confirming a single transit AS topology.

2. Nokia 4A0-106 Courseware, Module 3: BGP. The course material explains that as-override is a solution for customers using the same AS at multiple sites connected to a single provider. It details how the provider PE replaces the customer AS with its own, leading to the AS path seen in the output, which represents a path through the single provider AS.

In an Inter-AS Model C VPRN, the ingress PE (PE1) pushes a three-label stack onto the packet destined for the remote PE (PE2). This is required to traverse the multiple autonomous systems.

1. VPN Label (Innermost): This label is advertised by the egress PE (PE2) via the direct MP-eBGP session with PE1. It identifies the specific VPRN service instance on PE2.

2. BGP Label (Middle): This label is used for transport between the Autonomous System Boundary Routers (ASBRs). ASBR2 advertises a labeled route for PE2 to ASBR1, which then advertises it to PE1. This BGP label ensures the packet is correctly forwarded from ASBR1 to PE2.

3. Transport/LDP Label (Outermost): This label is learned via LDP within the source AS (AS1). It is used to forward the packet from PE1 to its BGP next-hop, which is ASBR1.

A. One label is insufficient for an Inter-AS scenario; it cannot provide transport across both the intra-AS and inter-AS links while also identifying the VPRN service.

B. A two-label stack is characteristic of Inter-AS Model B, where ASBRs exchange VPN-IPv4 routes and perform a label swap, not Model C.

D. Four labels are not used in a standard Inter-AS Model C deployment. This might be seen in more complex hierarchical models like Carrier-of-Carriers, but not this scenario.

1. Nokia 7750 SR OS Services Guide, Release 20.10.R1, VPRN Services, Section: Inter-AS VPRNs. This guide details the operation of different Inter-AS VPRN models. For Model C (Option C), it describes the data plane forwarding, which involves a three-label stack pushed by the ingress PE: an LDP label to reach the local ASBR, a BGP label to cross the inter-AS link and reach the remote PE, and the VPN label for service demultiplexing at the remote PE.

2. Rosen, E., & Rekhter, Y. (2006). BGP/MPLS IP Virtual Private Networks (VPNs). RFC 4364, Section 10. This foundational RFC describes the architecture for BGP/MPLS VPNs. Section 10, "Multi-AS Backbones," explicitly states for the Option C scenario: "This requires a label stack of depth 3. The top label takes the packet to the egress ASBR of the first AS. The middle label is the one assigned by the egress ASBR of the second AS for the egress PE. The bottom label is the VPN label."

3. Nokia 4A0-106 Courseware, Nokia Virtual Private Routed Networks, Module 4: VPRN Service Provisioning, Section: Inter-AS VPRNs. The official course material explains that in Model C, the data plane requires three labels to be imposed by the ingress PE to ensure end-to-end transport and service identification across the separate autonomous systems.

For VPRN services to function correctly, all Provider Edge (PE) routers must exchange VPN-IPv4 routing information. This is accomplished using Multi-Protocol iBGP (MP-iBGP). In the absence of route reflectors or confederations, the iBGP split-horizon rule mandates that all iBGP speakers within an Autonomous System form a full mesh.

Crucially, only the PE routers participate in the VPRN service control plane; the Provider (P) routers are only involved in MPLS label switching and do not need to process VPN routes. Therefore, the full mesh is only required among the 6 PE routers. The formula for the number of sessions in a full mesh is n (n - 1) / 2, where n is the number of routers.

Applying this formula: 6 (6 - 1) / 2 = 6 5 / 2 = 15.

A. 1: This represents a single session, which is insufficient for any network with more than two PE routers.

B. 5: This is the number of iBGP peers a single PE router would have (n-1), not the total number of unique sessions in the network.

D. 30: This incorrectly calculates the number of sessions as n (n-1), which double-counts each bidirectional BGP session.

E. 45: This incorrectly includes the 4 P routers in the full-mesh calculation (10 9 / 2 = 45). P routers do not participate in the VPRN iBGP control plane.

1. Nokia 7750 SR OS Services Architecture Guide, Release 21.10.R1, Section: VPRN Service Overview. This guide explains the BGP/MPLS IP VPN model. It states, "The PE routers distribute VPN-IPv4 routes to each other by means of the MP-BGP protocol... The P routers in the service provider core are not aware of the VPN routes." This confirms that only PE routers are part of the iBGP mesh for VPRN.

2. Nokia 7750 SR OS MPLS Guide, Release 21.10.R1, Section: BGP. This guide details the iBGP split-horizon rule and the resulting requirement for a full-mesh topology among iBGP speakers when route reflectors are not used. It implicitly supports the n(n-1)/2 calculation for the number of required sessions.

3. RFC 4364: BGP/MPLS IP Virtual Private Networks (VPNs), Section 4. BGP Extended Communities and their use in VPNs. This foundational RFC describes the architecture where "PE-routers use an interior BGP (iBGP) to distribute VPN-IPv4 routes to each other." It also clarifies that P-routers "do not need to run BGP at all." This supports the exclusion of P routers from the iBGP session calculation.

In a Carrier Supporting Carrier (CSC) VPRN model where the customer carrier is a BGP/MPLS service provider, the backbone carrier's PE (CSC-PE) routers do not learn or advertise the end-customer's routes. The backbone network's responsibility is to provide transport connectivity between the customer carrier's PE routers (CSC-CEs). The CSC-PEs use MP-iBGP to exchange labeled routes for the customer carrier's infrastructure (its PEs and P-routers), not the individual VPN routes of the end-customers. The customer carrier runs its own, separate MP-BGP sessions between its own PEs over the backbone. Therefore, the statement that MP-iBGP advertises end-customer routes is not applicable to the BGP/MPLS service provider customer type, and thus is not applicable to both types of customer carriers.

A. This is the standard and recommended method. The CSC-PE (backbone carrier) and CSC-CE (customer carrier) are in different autonomous systems, making eBGP the appropriate protocol for exchanging labeled routes.

B. While eBGP is standard, using iBGP is technically possible if the CSC-PE and CSC-CE are configured in the same AS. This configuration would be applicable to either customer carrier type.

C. This is the fundamental mechanism for the backbone VPRN. CSC-PE routers use MP-iBGP to distribute the customer carrier's routes (as VPN-IPv4 prefixes) across the backbone network to other CSC-PEs.

1. Nokia 3HE15095AAABTQZZA 01 - 7450 ESS, 7750 SR, 7950 XRS, and VSR Triple Play Service Delivery Architecture Guide, Release 20.10.R1, Section: "Carrier Supporting Carrier".

Page 598: "In the CSC model, the backbone carrier does not need to know the end-customer’s routes. The backbone carrier only needs to carry the customer carrier’s PE-to-PE routing information." This directly supports why option D is incorrect for the BGP/MPLS SP customer type.

Page 599: "The CSC-PE router uses an eBGP session to the CSC-CE router to send and receive labeled IPv4 routes." This confirms option A is correct.

Page 599: "The CSC-PE router uses an MP-iBGP session to other CSC-PE routers to send and receive VPN-IPv4 routes." This confirms option C is correct.

2. RFC 4364 - BGP/MPLS IP Virtual Private Networks (VPNs), Section 10: "Carrier's Carrier".

Page 29, Paragraph 2: "The backbone carrier's PEs (the 'CSC-PEs') do not need to know the routes to the end-customers' CEs... The CSC-PEs only need to know the routes to the customer carrier's PEs (the 'CSC-CEs')." This standard reinforces that the backbone carrier is agnostic to the end-customer routes, making statement D inapplicable to the BGP/MPLS SP scenario.

On the Nokia 7750 Service Router (SR), Virtual Private Routed Network (VPRN) services utilize Multiprotocol BGP (MP-BGP) to exchange customer routing information between Provider Edge (PE) devices. This is achieved by using the VPN-IPv4 address family (AFI=1, SAFI=128). To enable the exchange of these VPRN routes within a BGP session, the family vpn-ipv4 command must be configured under the BGP group or neighbor context. This command activates the VPN-IPv4 address family for that specific BGP peering, allowing the advertisement and reception of labeled VPN-IPv4 prefixes, which are essential for VPRN service operation.

B, C: The keywords vprn-ipv4 and vprn are not valid address family identifiers within the Nokia SR OS BGP configuration context. The correct identifier is vpn-ipv4.

D, E, F: The command address-family is the syntax used by other network operating systems, such as Cisco IOS. Nokia's SR OS uses the family keyword to configure BGP address families.

1. Nokia 7750 SR OS Services Guide, Release 22.10.R1: In the "Virtual Private Routed Network (VPRN) Services" chapter, the section "VPRN Configuration Overview" details the BGP configuration steps. It explicitly shows the use of the family vpn-ipv4 command to enable the exchange of VPRN routes between PE routers. (See section: "Basic VPRN Configuration" for command examples).

2. Nokia 7750 SR OS Routing Protocols Guide, Release 22.10.R1: The "BGP" chapter, under the "BGP Configuration Overview" and "Configuring BGP" sections, describes the command hierarchy. It specifies that the family command is used at the config>router>bgp>group and config>router>bgp>group>neighbor levels to enable specific address families, including vpn-ipv4.

The statement that eiBGP Load Balancing is enabled in the config>router>bgp context is false. This feature is specific to a Virtual Private Routed Network (VPRN) service and is configured within the service context itself. The correct command path is config>service>vprn>eibgp-load-balancing. The global BGP context is used for base protocol configuration, whereas service-specific BGP behaviors like eiBGP load balancing are configured within the VPRN instance to which they apply.

A. ecmp and multipath are indeed prerequisites. For any BGP-based load balancing to occur within a VPRN, these commands must be explicitly enabled in the config>service>vprn>bgp context.

B. This is a fundamental BGP loop-prevention mechanism. For a PE to accept a VPN-IP route from a remote PE for a prefix it also learns locally, the Route Distinguisher (RD) of the remote PE must be different.

D. This statement accurately describes the core function of eiBGP load balancing: it enables a PE to load share traffic for a specific destination across a direct eBGP path to a CE and an indirect MP-iBGP path through another PE.

1. Nokia 7750 SR OS Services Guide, Release 21.10.R1, Document Part Number: 3HE 17194 AAAD TQZZA, Section: VPRN Services > eiBGP Load Balancing.

This section explicitly states, "To enable eiBGP load balancing for a specific VPRN, the config>service>vprn>eibgp-load-balancing command must be configured." This directly refutes option C.

The same section confirms option A: "In addition, the ecmp and multipath commands must be configured in the config>service>vprn>bgp context."

It also confirms option B regarding the RD: "For eiBGP load balancing to work, the RD of the VPRN on PE1 must be different from the RD of the VPRN on PE2."

The introductory paragraph confirms option D: "The 7750 SR supports eiBGP load balancing, which allows a PE to forward traffic to a destination CE using both a direct CE-PE eBGP link and an indirect path through another PE..."

In an Inter-AS VPRN Model B architecture, the Autonomous System Boundary Routers (ASBRs) exchange VPN-IPv4 routes with other ASBRs using Multiprotocol eBGP (MP-eBGP). Within each Autonomous System (AS), the Provider Edge (PE) routers establish Multiprotocol iBGP (MP-iBGP) sessions with their local ASBR. As PE1 and ASBR1 are both within AS1, they use an internal BGP session. This session must support the VPN-IPv4 address family to carry VPRN routes, which necessitates the use of MP-iBGP. The ASBR effectively acts as a route reflector for the PE within its own AS for VPRN prefixes.

A. iBGP: This is incorrect because standard iBGP does not support the advertisement of VPN-IPv4 address family routes, which is a requirement for VPRN services.

B. eBGP: This is incorrect as eBGP is used for routing between different Autonomous Systems. The connection between PE1 and ASBR1 is within a single AS (AS1).

D. MP-eBGP: This is incorrect because MP-eBGP is used between ASBRs in different Autonomous Systems (e.g., between ASBR1 and ASBR2), not between a PE and an ASBR within the same AS.

1. Nokia 7750 SR and 7950 XRS Layer 3 Services Guide: VPRN, Release 22.10.R1, Document ID: DG-2210-0111.

Section: Inter-AS VPRNs > Inter-AS VPRN Model B

Quote/Paraphrase: This section explicitly states, "The PEs in each AS have MP-iBGP sessions to their local ASBR. The ASBRs in each AS are interconnected via MP-eBGP sessions." This confirms that the session between a PE (like PE1) and its local ASBR (ASBR1) is MP-iBGP.

2. Nokia Service Routing Architect (SRA) Self-Study Guide: Preparing for the BGP, VPRN and Multicast Exams, Document ID: SRC-SSG-BVM-R19.

Section: Chapter 4: Virtual Private Routed Network (VPRN) Services > Inter-AS VPRNs > Option B

Quote/Paraphrase: The guide describes Option B by detailing that VPN-IPv4 routes are distributed from the PE to the ASBR using MP-iBGP. The ASBR then redistributes these routes to the remote ASBR using MP-eBGP. This directly supports the use of MP-iBGP between PE1 and ASBR1.