The tethering setup worked beautifully in the demo — and died on day three. In almost every such story, the hardware was innocent: the data plan's fine print did it. This page is the fine print, translated.
Phone plans are sold on the big number — the monthly gigabytes — but tethering is governed by the small numbers underneath: how much of that data may be used as hotspot/tethering data, what speed applies after a fair-use threshold, and whether a daily cap resets the whole thing at midnight. One SIM feeding a whole router multiplies consumption in ways a single phone never did — every connected PC updates, syncs and streams as if it were on unlimited broadband. Check these four things before the network depends on the phone.
Illustrative consumption pattern for a small office on one SIM — your mix will differ, the order of magnitude will not.
Many plans separate phone data from hotspot data. A plan may advertise a large monthly allowance while hotspot use is capped much lower, or hotspot speeds drop after a fixed tethering quota. When a phone tethers into a router, all of the traffic counts as hotspot traffic — the carrier cannot see your individual devices, only that the phone is sharing. Read the plan's hotspot line specifically; the headline number is not the one that applies to you.
Cross the fair-use threshold and many plans do not cut you off — they throttle: speeds drop to a trickle (often well under 1 Mbps) until the cycle resets. Because it arrives as gradual slowness, it is routinely misdiagnosed as a router problem, a signal problem or a broken phone. The diagnosis is simple: check the carrier app's usage meter. If the meter says the threshold is crossed, no equipment change will help — only the cycle reset, a top-up, or a different plan will.
Popular prepaid-style plans reset a fixed amount of data per day. A single user barely notices; a router full of devices can burn the day's allowance before lunch — one OS update, one cloud-sync catch-up, one TV left streaming. If the setup must run on such a plan, discipline is the tool: schedule big updates outside this connection, set streaming quality down on shared screens, and consider a monthly postpaid-style plan with a real pool of data instead. The right plan is half of this entire setup.
Also keep plan terms in view: some carriers' conditions restrict or price tethering differently, and business use may belong on a business plan. Running inside the plan's terms keeps the arrangement boring — which is what infrastructure should be.
The wiring, the router settings and the live speed check — the complete process is shown in the video.
▶ Watch Full VideoAlmost certainly a plan threshold: either the hotspot allowance ran out or fair-use throttling kicked in. Both look exactly like a technical fault. Open the carrier's app and check the usage meter — if a limit is crossed, speed returns at the cycle reset, after a top-up, or on a plan with a larger tethering allowance.
The carrier sees tethering traffic from the phone — that detection is how hotspot caps are enforced — but it cannot see the individual devices behind your router. All of the shared traffic counts against the phone plan's hotspot/tethering terms.
A plan with a large single pool of data and a generous (or no separate) hotspot allowance — typically postpaid-style monthly plans rather than small daily-cap packs. Size it after one metered month of real usage rather than guessing, and confirm the tethering terms in writing if an office depends on it.