From CLI to Model: Building a Foundational Source of Truth for Brownfield Networks#

Munachimso Nwaiwu — Revelo (open-source project)

• Why: Addresses the barrier that stops most brownfield automation: no source of truth on a legacy network with no budget — with an open-source methodology and working code rather than advice.
• What: A three-step pipeline ("Revelo"): bootstrap an inventory (either explicit IP/credentials/platform, or discovered via nmap -O including hidden subnet devices), build a structured SOT by parsing live state into JSON, and validate state with automated diffs. Demonstrated on a multi-vendor lab (Cisco IOS/IOS-XE/NX-OS, Junos).
• How: NAPALM for vendor-neutral getters (facts, interfaces IPs, LLDP neighbors), Netmiko as the "truck" for CLI commands NAPALM doesn't cover, and Genie (pyATS) as the parser. The versioning design is the clever part: inventory/1/, sot/1_2/ (snapshot 2 under inventory 1), diff/1_2/ — producing an auditable history and two validation modes: live compliance ("is the network compliant right now?") and offline audit ("what changed last night?") with clean structured diffs instead of config noise.
• Where applicable: Broadly applicable to any brownfield network with programmatic CLI/API access — no greenfield or budget required, and the components are all mainstream open source. Limits: it captures operational state as the baseline, so your "intended state" is initially defined by whatever is actually running — a starting point, not a governance model.