A leaf loses all spine underlay peers and its server subnets become unreachable from the rest of the civic fabric. What routing principle explains that black hole?
Select an answer to reveal the explanation.
Short Explanation
If the leaf cannot talk to any spine, it cannot tell the fabric “these server nets live here”—and remote leaves stop knowing the path. Peer loss withdraws the underlay advertisement. Overlay magic does not float without underlay reachability.
Full Explanation
Leaf-attached prefixes are advertised into the IP fabric underlay so other leaves can route toward them. Loss of all underlay peers withdraws or otherwise removes that reachability from the fabric viewpoint. Server subnets are not independently flooded as L2 across a routed Clos underlay. VXLAN overlays still require underlay IP reachability to VTEP endpoints.