352-001 · Question #61
Service provider XYZ plans to provide dedicated Internet access and MPLS L3VPN services to business customers. XYZ has these design specifications: - MP-BGP running on the core MPLS P routers with…
The correct answer is B. Enable separate BGP control plane routers using a route reflector server concept that will be fully C. Enable all EBGP routers as route reflector servers and MPLS PE routers as their clients. Removing MP-BGP from MPLS P core routers is achievable by offloading BGP to dedicated route reflector servers and using EBGP peering routers as route reflectors for PE clients, keeping P routers focused solely on label switching.
Question
Service provider XYZ plans to provide dedicated Internet access and MPLS L3VPN services to business customers. XYZ has these design specifications:
- MP-BGP running on the core MPLS P routers with external Internet routes.
- The core network will include 16 Point of Presence IP POPs throughout the Asia-Pacific region.
- An additional nine non-P routers will use EBGP peering with multiple providers for Internet traffic.
- An additional 50 PE routers will provide end customers with dedicated Internet access and L3VPN
services throughout the Asia-Pacific region. In what two ways can the MP-BGP be removed from the MPLS P core routers and still provide dedicated Internet access and MPLS L3VPN services? (Choose two.)
Options
- ADisable BGP from the MPLS core P routers and have the MPLS core P routers run OSPF and LDP.
- BEnable separate BGP control plane routers using a route reflector server concept that will be fully
- CEnable all EBGP routers as route reflector servers and MPLS PE routers as their clients.
- DIt is not possible to disable BGP from the MPLS core P routers without impacting the dedicated Internet
How the community answered
(39 responses)- A26% (10)
- B59% (23)
- D15% (6)
Why each option
Removing MP-BGP from MPLS P core routers is achievable by offloading BGP to dedicated route reflector servers and using EBGP peering routers as route reflectors for PE clients, keeping P routers focused solely on label switching.
Running only OSPF and LDP on P routers provides label forwarding infrastructure but does not distribute Internet or VPN routing information to PE routers, which still require BGP to populate their VRFs and forward Internet traffic.
Deploying dedicated BGP route reflector servers offloads the full Internet and VPN routing table from P routers. P routers continue to forward labeled packets using LDP without needing to maintain BGP RIB entries, while the route reflectors distribute reachability to PE routers.
Configuring EBGP peering routers as route reflector servers with PE routers as clients allows Internet routes learned via EBGP to be reflected directly to PE routers. This removes the need for P routers to participate in BGP at all, as PE routers obtain routes from the EBGP-connected reflectors.
This is factually incorrect because architectures using route reflectors and separation of the BGP control plane from the data-plane P routers are well-established designs that preserve both Internet access and L3VPN services.
Concept tested: BGP route reflector offload from MPLS P routers
Source: https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/iproute_bgp/configuration/xe-16/irg-xe-16-book/bgp-route-reflectors.html
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