In Apstra, a collapsed fabric (also described as “spineless”) consolidates traditional fabric tiers so that the primary fabric devices perform combined roles. Instead of a dedicated spine tier providing transit between leafs, the fabric is formed by leaf devices connected directly to each other using mesh links. This means a collapsed fabric uses a full-mesh topology at the leaf level, replacing the usual leaf-to-spine connections found in a three-stage Clos. Therefore, the statement that leaf devices are full-mesh connected is correct.
Because the collapsed fabric devices serve the fabric roles, they also provide the EVPN-VXLAN overlay functions (VTEP behavior, EVPN control-plane participation, and VXLAN encapsulation/decapsulation) necessary for tenant segmentation and service delivery. Juniper’s collapsed fabric validated designs further describe the collapsed fabric switches as serving all fabric roles (including border-leaf behaviors when external connectivity is required), reinforcing that overlay functions reside on these fabric leaf devices.
The remaining statements are not generally true for the collapsed fabric definition. Top-of-rack (access) switches—when present in certain collapsed designs—are not defined by default as full-mesh connected, and VXLAN support is not a requirement for those TOR/access switches unless the specific architecture explicitly uses them as VTEPs. The defining characteristics are the consolidated fabric roles and the leaf-level full-mesh.
Verified Juniper sources (URLs):
https://www.juniper.net/documentation/us/en/software/apstra5.0/apstra-user-guide/topics/concept/templates.html
https://www.juniper.net/documentation/us/en/software/apstra4.2/apstra-user-guide/topics/concept/rack-types.html
https://www.juniper.net/documentation/us/en/software/jvd/jvd-collapsed-dc-fabric-with-apstra/jvd-collapsed-dc-fabric-with-apstra.pdf
