Right Size Your Box

Right-Size Your Box

✅ Guidance, not software — this page is just advice, so nothing here is waiting on a build. The hardware catalogue it summarises is docs/HARDWARE.md.

The short version: you almost certainly need less than you think. 2.5GbE is headroom for gigabit inline shaping — it is not a baseline. Most people need one network port on almost anything.

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First, answer one question: sidecar or gateway?

This decides everything else. It is the fork in the road.

	Sidecar (the majority path)	Gateway (the enthusiast path)
Sits	Beside your router	Between your modem and your LAN
Does	DNS sinkhole, print, time, firewall-for-itself, monitoring	All of that + CAKE traffic shaping
Needs	1 network port, almost any CPU	2 network ports, a fast single core
If it dies	Ads come back. Internet keeps working.	Everything routes through it — so it must fail-open
Runs on	A Pi 2B. Genuinely.	An x86 N100 for gigabit

Start as a sidecar. It's the low-risk, high-value 90 %. Only go gateway if you have a specific problem shaping solves — see below.

Do you actually need the shaper?

Only if you have bufferbloat: the thing where a video call breaks up while someone uploads, or your ping triples during a download. Your idle ping is probably already fine and shaping won't improve it.

Test it in 30 seconds, before buying anything: run waveform.com/bufferbloat on a wired machine. It grades your latency under load.

Grade	What to do
A / A+	You don't need the shaper. Stay a sidecar. Spend the money on nothing.
B / C	Shaping will give you a real, noticeable win.
D / F	Shaping will feel transformative.

On this project's own line (Virgin Media, ~1 Gb cable): idle was already excellent — ~12 ms, <1 ms jitter, 0 % loss. Under upload saturation it went to 24 ms average / 56 ms max, jitter 1.5 → 9.4 ms — a solid B/C. That's the gap the shaper closes, and it's the only reason the N100 is in this design.

Match the box to your line

The rule: NIC and CPU scale with line speed, not with a fixed spec sheet.

Your connection	For inline shaping	For a sidecar
Gigabit+ cable/fibre	N100 + 2× 2.5GbE (Intel i226-V)	Anything, 1 port
Sub-gig, ≤ ~500 Mbps	1GbE + modest CPU — a Pi 4 copes	Any Pi / mini-PC, 1 port
VDSL, ~40–80 Mbps	Onboard 1GbE is plenty — a Pi 2B is fine	A Pi 2B is fine
5G / 4G home box, hotspot	Usually impossible — they won't bridge → sidecar. The radio is your bottleneck anyway.	1 port, anything

Why an N100 and not a Pi 5?

Because CAKE is essentially single-threaded. This is the single most useful fact on this page, and it's counter-intuitive:

• Cores don't help. Shaping runs on one.
• RAM doesn't help. It's not the constraint.
• A GPU doesn't help at all — which is why a Jetson is the wrong tool here despite sounding powerful. Its A57 CPU is weaker than a Pi 4's.

Practical ceilings, roughly:

Box	Shaping ceiling
Pi 2B	Not a gateway at all — 100 Mbit NIC on the shared USB 2.0 bus
Pi 3 / Jetson	Well under a gigabit
Pi 4	~350–500 Mbit
Pi 5	~600–900 Mbit
Intel N100	~1–2.5 Gbit ✅

So for a gigabit line, the N100 is the first box that actually clears it.

If you buy an N100, spend the money in the right place

• ✅ Base N100 is enough. An N305/N150 buys you nothing for pure routing — more cores don't shape faster.
• ✅ Spend on the NICs: 2× Intel i226-V. Avoid Realtek 2.5GbE — the driver situation is the thing that'll actually waste your evening.
• ✅ Fanless is nice. ~10 W is normal.

The Pi 2B is not a failure case

It's a genuinely excellent DNS sinkhole, print server, firewall, DDNS client, and link monitor — the dependable, boring, always-on Core. Its honest ceiling is in docs/LEGACY-DEVICES.adoc:

• armv7 / 32-bit → no Wolfi, so Alpine.
• 1 GB RAM → no ClamAV (1–2 GB signature DB), no local metrics database.
• 100 Mbit NIC on the USB 2.0 bus → never a credible router.
• No onboard RTC → add a DS3231 (~£3).
• SD storage → read-only root and bounded logging, or the card wears out.

The greenest box is the one you already own. Reuse beats buying: embodied carbon (manufacturing) often outweighs years of the ~10 W this thing draws. If a spare 2B does the job, that is the better answer — not a consolation prize.

Where next

• Getting Started — the sidecar path, today, on what you have
• Tested Devices — what people have actually run
• Estate Architecture — why it's two boxes, not one