352-001 · Question #301
You are the lead IP network designer for a new service provider called XYZ, and you are working closely with the CTO to finalize design requirements. The CTO informs you that they want to transport IP
The correct answer is B. Use MPLS 6PE to simplify the operation and keep a BGP-free core. D. Prepare the dual-stack infrastructure from the beginning, even if BGP prefixes would have to be. MPLS 6PE is the recommended approach for transporting customer IPv6 prefixes over an IPv4 MPLS core because it avoids introducing IPv6 into the core while keeping it BGP-free, and preparing dual-stack infrastructure early ensures long-term flexibility.
Question
You are the lead IP network designer for a new service provider called XYZ, and you are working closely with the CTO to finalize design requirements. The CTO informs you that they want to transport IPv6 prefixes of customers through the XYZ network at this time; however, they need your advice on whether to deploy dual stack or MPLS 6PE/6VPE. Which two options do you recommend? (Choose two.)
Options
- ABuild a dual-stack network. Enable BGP in the core.
- BUse MPLS 6PE to simplify the operation and keep a BGP-free core.
- CUse MPLS 6VPE to simplify the operation and keep a BGP-free core.
- DPrepare the dual-stack infrastructure from the beginning, even if BGP prefixes would have to be
How the community answered
(63 responses)- A25% (16)
- B62% (39)
- C13% (8)
Why each option
MPLS 6PE is the recommended approach for transporting customer IPv6 prefixes over an IPv4 MPLS core because it avoids introducing IPv6 into the core while keeping it BGP-free, and preparing dual-stack infrastructure early ensures long-term flexibility.
Enabling BGP in the core (P routers) introduces significant scalability and operational complexity, defeating the purpose of an MPLS architecture where the core remains BGP-free and only processes labeled packets.
MPLS 6PE tunnels customer IPv6 prefixes across an IPv4/MPLS core by encoding IPv6 routes as labeled BGP updates only at PE routers, keeping P routers IPv4-only and BGP-free. This simplifies core operations while enabling immediate IPv6 service delivery to customers.
MPLS 6VPE is designed for transporting IPv6 VPN (L3VPN) customer prefixes with full VRF separation, which adds unnecessary complexity when the requirement is simply to transport customer IPv6 prefixes without managed VPN isolation.
Deploying dual-stack infrastructure from the outset - even while running MPLS 6PE - ensures that the network is ready to support native IPv6 services or a full transition later without requiring a costly re-architecture of physical or logical layers.
Concept tested: MPLS 6PE for IPv6 transport with BGP-free core
Source: https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/iproute_bgp/configuration/xe-16/irg-xe-16-book/bgp-support-for-6pe.html
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