In this document, a Clos leaf-spine topology is used for each availability zone. Individual switch configuration shows how to set up end-to-end Virtual Extensible Local Area Networks (VXLANs). External Border Gateway Protocol (eBGP) is used for exchanging IP routes in the IP underlay network, and EVPN routes in the VXLAN overlay network. Virtual Link Trunking (VLT) is deployed between leaf pairs and internal BGP (iBGP) to provide Layer 3 path redundancy in the event a leaf switch loses connectivity to the spine switches.
Figure 8. Layer 3 IP network transport