VXLAN Underlay Routing - Part II: OSPF and IS-IS from the VXLAN network perspective

Now you can also download my VXLAN book from the Leanpub.com 

"Virtual Extensible LAN VXLAN - A Practical guide to VXLAN Solution Part 1. (373 pages)

This chapter discusses the differences between the OSPF and the IS-IS from the Network Virtualization Overlay (NVO) solution, especially from the VXLAN network perspective. First, this chapter shortly introduces some of the differences between these two protocols (terminology, timers, and LSAs). Next, this chapter explains the default behavior of the Shortest Path First (SPF) by explaining first the IS-IS reaction when Stub Network goes down. Then the same event is explained from the OSPF perspective. This chapter also introduces OSPF reaction when an Incremental SPF (iSPF) is enabled, and the interface on a link that is not belonging to the Shortest-Path Tree (SPT) goes down. The same event is also discussed with and without iSPF concerning IS-IS. 

Figure 1-1: Comparison of OSPF and IS-IS.

VXLAN Underlay Routing - Part I: OSPF and Dijkstra/SPF algorithm

Now you can also download my VXLAN book from the Leanpub.com 
"Virtual Extensible LAN VXLAN - A Practical guide to VXLAN Solution Part 1. (373 pages)

The role of the Underlay Network

Underlay Network the main job from the EVPN VXLAN Network Virtualization Overlay (NVO) solutions perspective is to offer resilient IP connectivity between the Network Virtualization Edge Interfaces (NVE) on VXLAN Tunnel End Point (VTEP) devices. In addition, the Underlay Network can be used for BUM traffic forwarding (Broadcast, Unknown Unicast, and Multicast) though this solution requires a Multicast Routing enabled on an Underlay Network. The common routing protocols choices for VXLAN Underlay Network are OSPF, IS-IS which are Link State Protocols and BGP which in turn is Path Vector Protocol. The focus of this chapter is the Dijkstra/Shortest Path First (SPF) algorithm that Link State Protocols uses for calculating the Shortest-Path Tree. Figure 1-1 shows the Link type-1 (point-to-point) and Link Lype-3 (Stub Network) Routers LSA originated by Leaf-101, Leaf-102, Spine-11, and Spine-12. In addition, figure 1-1 illustrates how routers form a topology based on received LSAs.

Figure 1-1: Examples of Link type-1 (p2p) and Link-Type 3 (Stub) Router LSAs.