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Difficulty: EasySoftware-Defined Architectures: Overlay, Underlay, and Fabric

An engineer is deploying a software-defined fabric architecture across an enterprise network. Which two operational functions are handled exclusively by the overlay network rather than the underlying physical network? (Choose two.)

  1. Encapsulating virtual tenant traffic inside VXLAN packets at the fabric edgeAnswer
  2. B
    Establishing physical IP reachability between fabric nodes using an IGP like OSPF or IS-IS
  3. Maintaining the mapping database that resolves Endpoint Identifiers (EIDs) to Routing Locators (RLOCs)Answer
  4. D
    Forwarding packets across core fabric switches based on the outer destination IP header
  5. E
    Configuring maximum transmission unit (MTU) sizes to accommodate encapsulation overhead on physical interfaces

Answer

Encapsulating virtual tenant traffic inside VXLAN packets at the fabric edge and maintaining the mapping database that resolves Endpoint Identifiers (EIDs) to Routing Locators (RLOCs) are the two functions operating exclusively within the overlay network.
In software-defined network fabrics, the overlay network is responsible for creating virtual networks on top of physical infrastructure. Encapsulating traffic using VXLAN at fabric edge nodes forms the overlay data plane, while maintaining the LISP mapping database (EID to RLOC) forms the overlay control plane.

Step-by-Step Solution

1
Identify the primary role of the overlay network.
The overlay network provides virtualized layer 2 and layer 3 connectivity on top of the underlay using encapsulation and mapping protocols.
Overlay architectures decouple endpoint identity and virtual topology from the physical network infrastructure.
2
Evaluate data plane mechanisms.
VXLAN encapsulates original tenant frames with outer headers at Virtual Tunnel Endpoints (VTEPs).
This packet encapsulation allows virtual networks to span across physical IP boundaries.
3
Evaluate control plane mechanisms.
LISP maintains mapping tables between EIDs (endpoint addresses) and RLOCs (underlay IP addresses).
LISP serves as the control plane for locating endpoints within the fabric overlay.

Key Concept

Overlay vs. Underlay Roles in Software-Defined Networking
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Topics

Software-Defined Architectures: Overlay, Underlay, and Fabric

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