Which of the following statements regarding BGP shortcuts is FALSE?

The primary benefit of BGP shortcuts (also known as BGP Labeled Unicast) is to enable a BGP-free core network. In this architecture, edge routers (PEs) run BGP to exchange routing information. However, the transit routers (P-routers) in the core do not need to run BGP. Instead, they only need to be MPLS-enabled (running LDP or RSVP-TE) to perform label switching. The ingress edge router encapsulates the IP packet in an MPLS label stack and forwards it across an LSP to the BGP next-hop (the egress edge router). This eliminates the need for transit routers to have BGP routes, simplifying core router configuration and reducing processing overhead.

A. MPLS tunnels are used to carry transit traffic across the network. This is true. BGP shortcuts rely on MPLS Label Switched Paths (LSPs), which function as tunnels, to forward traffic from an ingress router to the BGP next-hop across the core.
B. A full mesh of iBGP peering sessions is not required. This is true. By using MPLS to forward traffic to the BGP next-hop, BGP shortcuts help avoid the need for intermediate routers to participate in the iBGP mesh, thus simplifying the iBGP topology.
D. The transit routers need to support LDP or RSVP-TE LSPs. This is true. For the MPLS tunnels to be established, the transit routers must run a label distribution protocol, such as LDP or RSVP-TE, to build the LSPs that carry the BGP traffic. ---

1. Nokia 7750 SR OS R21.10.R1 BGP Configuration Guide, Document Part Number: 3HE-17358-AAAA-TQZZA 01.

Section: BGP Labeled Unicast Routes for BGP Shortcut: "The ingress router resolves the BGP next hop of the prefix using an RSVP or LDP LSP. This allows the BGP traffic to be transported over the MPLS core without the core routers needing to have the BGP route in their routing table." This statement directly confirms that transit (core) routers do not need BGP, making option C false. It also validates options A and D.

2. Nokia Data Center, IP and Optical Networks, "Scaling BGP" Courseware Material.

Module: BGP Scaling Mechanisms: "BGP shortcuts leverage an underlying MPLS transport infrastructure (LDP or RSVP-TE) to forward traffic to BGP next-hops. This design creates a 'BGP-free core,' where P routers only perform label switching and do not participate in BGP. Only the PE routers at the edge of the network require BGP configuration." This source explicitly states that transit (P) routers are BGP-free, reinforcing that statement C is false.