Create homelab-dns-decision.md via n8n

Tech/Sessions/homelab-dns-decision.md

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+---
+project: homelab-dns-decision
+type: session-notes
+status: active
+path: Tech/Sessions
+tags:
+  - homelab
+  - dns
+  - knot
+  - pihole
+  - unbound
+  - traefik
+created: 2026-05-06
+updated: 2026-05-06
+---
+# Homelab DNS — Architecture Decision
+
+## Outcome
+
+Locked the internal DNS architecture. **Knot DNS** as a dedicated
+authoritative server for `herbylab.dev`, running active/passive across
+Proxmox and the NAS. Pi-hole + Unbound stays as the recursive frontend and
+ad-blocker.
+
+## Architecture
+
+
+Client → Pi-hole (ad-block + cache)
+           ├─ herbylab.dev queries → Knot (authoritative)
+           └─ everything else      → Unbound → root servers
+
+
+Split-horizon: `*.herbylab.dev` resolves internally to the Traefik VM IP
+via Knot. Cloudflare remains public authoritative for the same zone. Same
+name, different answer depending on who's asking.
+
+## Decisions
+
+| Decision | Choice | Rationale |
+|---|---|---|
+| Authoritative DNS | Knot DNS | Purpose-built authoritative, native
+AXFR/NOTIFY, ~40MB RAM, zone files in plain text, `knotc` CLI for runtime
+changes |
+| Recursive + ad-block | Pi-hole + Unbound (kept) | Already works, no
+reason to replace the recursive layer just because zone management is
+clunky |
+| Redundancy model | Active/passive, separate hosts | Knot primary on PVE,
+secondary on NAS — separate failure domains |
+| Replication | Native AXFR + NOTIFY | Edit primary, secondary auto-syncs.
+No Ansible run per record change |
+| Source of truth | Zone file in git | Versioned, debuggable, deployed to
+primary via Ansible |
+| Failover at client | OpenWrt DHCP hands out both Pi-hole IPs |
+Active/passive at the resolver level. Adds the second Pi-hole to the
+existing pattern |
+| DHCP | Stays on OpenWrt | Knot doesn't touch DHCP |
+| Internal certs | Wildcard `*.herbylab.dev` via Traefik + Cloudflare
+DNS-01 | Real LE cert, no browser warnings, independent of internal DNS
+layer. Works because Cloudflare owns the public zone — LE never touches the
+internal IP |
+| Zone structure | Flat (one zone for all `*.herbylab.dev`) | Single source
+of truth; revisit if it gets unwieldy |
+
+## Why Not the Other Contenders
+
+- **Technitium** — right answer when *replacing* Pi-hole + Unbound
+entirely. Overkill once Pi-hole stays.
+- **PowerDNS** — sexy on paper (REST API, web UI option) but adds SQL
+backend, second daemon for the UI, heavier replication setup. Can write a
+custom GUI on top of Knot later if needed.
+- **CoreDNS** — fine, but not really designed for primary/secondary AXFR.
+Better fit for K8s-style deployments.
+- **NSD** — close runner-up. Knot edged it on the `knotc` runtime CLI and
+slightly nicer config syntax.
+- **BIND9** — overkill, config-heavy. Skipped.
+
+## Key Learnings
+
+- **Internal certs are a naming problem, not a DNS problem.** Using `
+herbylab.dev` for internal names (split-horizon) means a public CA will
+sign a wildcard cert via DNS-01. A `.lan` or `.internal` zone forces a
+private CA + root cert distribution — not worth it.
+- **The job defines the tool.** Original DNS contender list (Technitium,
+CoreDNS, PowerDNS, BIND9) assumed a full Pi-hole + Unbound replacement.
+Once Pi-hole stays, the job collapses to "small authoritative server, one
+zone, easy to replicate" — different list (Knot, NSD, CoreDNS, PowerDNS).
+- **Cloudflare, Tailscale, Traefik, internal DNS each do one thing.**
+Cloudflare = public auth + ACME validation. Tailscale MagicDNS = device
+naming on the tailnet. Traefik = service routing once a request lands.
+Internal DNS = telling LAN clients where to send the packet. They don't
+overlap, they compose.
+
+## Open Items
+
+- [ ] Stand up second Pi-hole instance for redundancy (parallel to Knot
+work, not blocking)
+- [ ] Decide Pi-hole sync method (gravity-sync vs Teleporter)
+- [ ] Pick deployment unit for Knot on each host (LXC on PVE likely; Docker
+on NAS)
+- [ ] Initial zone file content — inventory current `*.herbylab.dev`
+records to migrate from Pi-hole local DNS
+- [ ] TTL strategy — start at 300 during buildout, raise to 3600 once stable
+- [ ] Ansible role for Knot primary deployment
+- [ ] Confirm Pi-hole conditional forwarding config for `herbylab.dev` →
+Knot
+
+## Next Session
+
+Return to the Traefik chat with this decision locked. DNS slot in the
+broader stack is now filled.
+
+
+
+
+...sent from Jenny & Travis