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This chapter continues our deep-dive into the different Cisco SD-WAN operations by exploring the control plane. The chapter is broken into six distinct sections:

  • Theory#1: Underlay vs. Overlay routing
  • Theory#2: Control Connections
  • Theory#3: vSmart
  • Theory#4: Overlay Management Protocol
  • Theory#5: OMP Best-path Algorithm
  • Theory#6: VPNs and Labels

The first section examines the difference between the underlay and the overlay routing. Then we discuss the process of establishing control connections to each SD-WAN controller. The third section of this chapter quickly introduces the vSmart controller. Then, we explore the Overlay Management Protocol (OMP) and see how vSmart uses OMP to facilitate the control-plane function across the overlay fabric. In the last section, we deep-dive into the OMP best-path algorithm and then go through the following practical examples:

  • Lab#6.1: Understanding OMP routing – The basics.
  • Lab#6.2: Understanding OMP routing - Send Path Limit.
  • Lab#6.3: Understanding OMP routing - Send Backup Paths.
  • Lab#6.4: Reducing control-plane traffic on LTE WAN links.