BGP unnumbered is one of those data-center fabric features that looks almost too simple when it works: no per-link IPv4 addressing, a repeatable interface template, and eBGP sessions built over IPv6 link-local addresses. The operational catch is that the failure mode moves from “is this /31 correct?” to “is neighbor discovery, peer discovery, policy and next-hop resolution all aligned?”
This post is a practical checklist for building and troubleshooting a small leaf-spine fabric with BGP unnumbered. It is vendor-neutral in structure, with sample commands shown as patterns rather than copy-paste production configuration.
