In Apstra, a logical device abstracts a physical switch's front-panel layout into one or more panels containing port groups. Each port group has a defined speed and one or more roles that describe how those ports are expected to be used in the fabric. These roles are essential because they constrain where ports may be consumed during rack type and template construction (for example, spine-facing vs server-facing vs generic connectivity).

Apstra-supported port group roles include fabric roles such as Spine and Leaf, and endpoint-facing roles such as Generic (commonly used for ports that connect to servers or external generic systems). Assigning Leaf and Spine roles ensures Apstra can correctly validate and render intent for uplinks and interconnects in a three-stage Clos or larger topologies. Assigning Generic indicates ports that can be used for non-fabric connections (such as server links, external routers modeled as generic systems, or other non-managed endpoints).

The options Empty and Root are not valid Apstra port group roles in the logical device model; Apstra uses other explicit role names (for example, Access, Peer, Unused, Generic, Leaf, Spine, Superspine depending on design type and version). In Junos v24.4 EVPN-VXLAN fabrics, getting these roles correct is foundational because Apstra relies on them to place underlay and overlay configuration onto the right interfaces with predictable results.

Verified Juniper sources (URLs):

https://www.juniper.net/documentation/us/en/software/apstra4.2/apstra-user-guide/topics/concept/logical-devices.html

https://www.juniper.net/documentation/us/en/software/jvd/jvd-collapsed-dc-fabric-juniper-apstra-access-switches/configuration_walkthrough.html