If Route Reflector 1 (RR1) is used for Internet routes, and Route Reflector 2 (RR2) is used for VPN routes, which of the following is TRUE?

In a scaled BGP design where different route reflectors (RRs) are used for different services, the BGP sessions are typically configured to support only the necessary address families. RR1, designated for Internet routes, will have iBGP sessions with Provider Edge (PE) routers that are enabled exclusively for the IPv4 unicast address family. This is because Internet routes are standard IPv4 prefixes. Conversely, RR2, designated for VPN routes, will have its iBGP sessions with PEs enabled for the VPN-IPv4 address family to exchange customer VPN prefixes. This separation provides better scalability, easier management, and fault isolation between the Internet and VPN routing domains.

A. The BGP sessions with RR2 are for VPN routes, which use the VPN-IPv4 address family. Including the standard IPv4 address family is unnecessary and contradicts the design's separation of roles.

C. RR1 is explicitly designated for Internet routes. The BGP sessions established with it would not be configured to carry VPN-IPv4 routes, as that is the role of RR2.

D. RR2 is used for VPN routes, which are exchanged using the VPN-IPv4 address family (AFI 1, SAFI 128), not the standard IPv4 address family (AFI 1, SAFI 1).

1. Nokia 7750 SR OS MPLS Guide, Release 21.10.R1, Section: BGP/MPLS IP VPNs: This guide details the mechanism for L3VPNs. It states, "BGP is used to distribute VPN routing information between PE routers... When BGP is used to distribute VPN routes, the VPN-IPv4 address family must be enabled." This confirms that a dedicated RR for VPN routes (RR2) must support the VPN-IPv4 address family. The separation of RRs implies that the Internet RR (RR1) would not have this family enabled.

2. Nokia 7750 SR OS Services Architecture Guide, Release 21.10.R1, Section: VPRN Service Overview: This document describes the fundamental architecture of Virtual Private Routed Network (VPRN) services. It explains that BGP distributes VPN-IPv4 NLRI (Network Layer Reachability Information) between PE routers. The design choice to use separate RRs for Internet (IPv4) and VPN (VPN-IPv4) routes is a common scaling technique to isolate the routing planes, meaning the session to the Internet RR would only need the IPv4 address family.

3. Nokia Data Center Fabric with EVPN and VXLAN Solution Guide, Release 2.0, Section 3.2.2.2 "Route Reflector Placement": While discussing EVPN, this solution guide reinforces the design principle of using separate sets of route reflectors for different address families (e.g., underlay address-family IPv4/IPv6 and overlay address-family EVPN). This principle of functional separation is directly applicable to the scenario of separating Internet (IPv4) and L3VPN (VPN-IPv4) route reflection for scalability and stability.