When a routing protocol is configured as the PE-CE protocol at one site of a customer VPRN, the same routing protocol must be configured as the PE-CE protocol at all other sites of the same customer VPRN.

The statement is false. A fundamental feature of a VPRN (Virtual Private Routed Network) service, which is based on the IETF standard for BGP/MPLS IP VPNs (RFC 4364), is the ability to support different PE-CE (Provider Edge to Customer Edge) routing protocols at various sites belonging to the same customer VPRN. The PE router acts as a boundary, performing route redistribution. It learns routes from a CE device using one protocol (e.g., OSPF at Site A), redistributes these routes into MP-BGP to be carried across the provider's MPLS core, and then at a remote PE router, redistributes them from MP-BGP into the local PE-CE protocol (which could be BGP, RIP, or even static routing at Site B). This architecture decouples the routing protocols used at each customer site, providing significant flexibility for both the service provider and the customer.

The "True" option is incorrect because it contradicts the core design and a primary advantage of MPLS L3VPN/VPRN services. Forcing a single PE-CE routing protocol across all sites would be a significant and unnecessary limitation, removing the flexibility that the MP-BGP-based architecture is designed to provide.

1. Nokia 7750 SR OS Services Guide, Release 22.10.R1, "VPRN services" chapter, Section: "PE-CE routing protocols". This section details the configuration of various routing protocols (BGP, OSPF, RIP, IS-IS) and static routing between PE and CE routers. The documentation describes configuring these protocols on a per-interface (per-site) basis within a single VPRN service, implicitly and explicitly demonstrating that different sites can use different protocols. For example, one sap can be in an OSPF area while another sap in the same VPRN service can have a BGP neighbor relationship configured.

2. Nokia Virtual Private Routed Network Service Student Guide, Course Number 4A0-106, Module 3: VPRN Routing. This official courseware explains the VPRN architecture. It explicitly states that the PE router can run different routing protocols with different CEs for the same VPRN. It details the process of route redistribution from a PE-CE protocol into MP-BGP and vice-versa, which is the mechanism that enables this flexibility.

3. Stallings, W. (2016). Foundations of Modern Networking: SDN, NFV, and Cloud Computing. Pearson Education, Inc. Chapter 11, Section 11.4 "MPLS Virtual Private Networks". While a general textbook, it is representative of university-level courseware. This chapter explains the architecture of RFC 4364 L3VPNs. It describes the role of the PE router in isolating the customer's routing from the provider's core and from other customer sites. It clarifies that the PE-CE protocol is a local matter for each site and that MP-BGP is used to stitch the sites together, allowing for heterogeneous PE-CE routing protocols.