CCNP Practice Question: A network architect is designing an SD-Access…

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

• ✓

  LISP and VXLAN

  Why this is correct

  In Cisco SD-Access, LISP serves as the overlay control plane by storing endpoint identifiers and mapping them to routing locators, enabling host mobility, segmentation, and scalable forwarding decisions. VXLAN is the overlay data plane, wrapping Ethernet frames in UDP/IP with a VNI that isolates tenants and virtual networks. Together they decouple the logical fabric from the physical underlay, allowing arbitrary Layer 2 and Layer 3 topologies over a routed IP fabric.

• ✗

  MP-BGP and MPLS

  Why it's wrong here

  MP-BGP with MPLS is the core of service provider MPLS L3VPN designs, where VPNv4/VPNv6 routes are exchanged between PE routers and labels are pushed/popped over an LSP. Cisco SD-Access does not use an MPLS label-switched forwarding path; its overlay carries a UDP header (VXLAN) and uses LISP-based Map-Server/Map-Resolver signaling instead of BGP VPN labels. Attempting MPLS would require LDP/RSVP and label distribution, adding complexity rather than the lightweight mapping system SD-Access uses.

• ✗

  OSPF and GRE

  Why it's wrong here

  OSPF is an underlay IGP that can be used for reachability between fabric devices in SD-Access, but it is not part of the overlay control plane; LISP handles that role. GRE is a generic point-to-point or multipoint tunnel, but the SD-Access data plane uses VXLAN, which provides MAC-in-UDP with a 24-bit VNI for scalable segmentation. GRE lacks a true network segment identifier and the efficiency of mapping host endpoints to locators, so the pair is unsuited for SD-Access architecture.

• ✗

  IS-IS and NVGRE

  Why it's wrong here

  IS-IS is often deployed as an underlay routing protocol in SD-Access networks to build IP connectivity, so its use alone does not define the overlay. NVGRE (Network Virtualization using GRE) is a competing overlay standard that uses GRE headers with a 24-bit Virtual Subnet ID, but Cisco SD-Access specifically chose VXLAN for data-plane encapsulation and LISP for control-plane state. Mixing IS-IS on the underlay with NVGRE on the overlay does not match the Cisco SD-Access fabric design and fails to deliver the required LISP-based host mobility and policy integration.