Match your symptom to the fix.

“My router's WAN speed test reads full speed, but every device caps at roughly half — wired and wireless both”

Hardware NAT acceleration on your router has been silently disabled by a feature you enabled and forgot about. The CPU is forwarding every packet in software, which most consumer router SoCs top out around 400–600 Mbps doing.

“I'm paying for gigabit (or close to it) and consistently getting a fraction of that, on a known-good wired connection”

Real delivery gap. You've already done the customer-side rule-outs; the line is the problem. The fix is structured escalation, not more router config.

“Wi-Fi works fine on my phone, but it's terrible on my PC in the same room”

The network isn't the variable. The device is. Almost always something specific to the PC: power management, an old Wi-Fi card, antenna position, or a USB 2.0 port choking a USB Wi-Fi adapter.

“My wired ethernet is capped at exactly 90 (or ~94) Mbps no matter what device or speed test I use”

Your link has auto-negotiated from Gigabit (1000BASE-T) to Fast Ethernet (100BASE-TX). The protocol downshift happens when any one of the four wire pairs fails the Gigabit handshake. Almost always a damaged cable.

“My powerline adapter is rated 'gigabit' or 'AV2000' but I'm only getting 50–150 Mbps”

Powerline PHY rates are theoretical maximums under lab conditions. Real-world throughput runs 30–50% of the advertised number on a good install, much less on a bad one. Your wiring topology, appliance noise, and outlet phasing all chew the signal.

“I added more Eero (or other mesh) nodes and Wi-Fi got worse, or devices keep switching between satellites”

Mesh oversaturation. In small or medium spaces, too many wireless nodes create overlapping coverage zones, force constant roaming decisions, and share spectrum between client traffic and backhaul. More nodes is not always better.

“I have coax in my walls and want a wired-quality connection without drilling for ethernet”

MoCA is the right tool for this. It uses the existing coaxial cable network in your walls to deliver near-gigabit ethernet between any two rooms with coax jacks. A pair of MoCA 2.5 adapters runs $130–180 and installs in 30 minutes.

“I'm running ethernet and don't know if I should buy Cat6, Cat6a, Cat7, or Cat8”

Cat6 is the home-network floor in 2026. Cat6a is the future-proof choice for any in-wall run or for 10 GbE service. Cat7 is marketing — not a TIA standard. Cat8 is data-center cable, overkill for home.

“I think I'm overpaying for an internet plan that's bigger than I actually need”

Probably true. Most homes don't need more than 300–500 Mbps; the community on r/HomeNetworking is unanimous about this. ISP middle tiers are engineered to make the top tier look like a steal — the cheapest tier is usually the right answer.

“My speed test says I have a fast connection, but my actual downloads are way slower”

Speed tests measure parallel TCP burst against a peered server. Real downloads use single-stream TCP against an arbitrary server with its own upload bandwidth, peering, and congestion. The two are measuring different things; the gap can be 5–25×.

“It was working fine, now it isn't, and I don't know what changed”

Time-shift regression. Common causes are a recent firmware update (router or OS), a cable that degraded across a threshold, or feature accumulation on a router that's gotten progressively more loaded over months.

“Microsoft Teams keeps showing “Your network is causing poor call quality””

Teams is measuring a specific metric — the concealed sample ratio — and yours crossed 1.72%. The warning means audio packets are being dropped fast enough that the codec is interpolating more than it should. Almost always Wi-Fi link quality, bufferbloat under load, or a VPN routing detour.

“I don't understand what the numbers in my router app mean — is the live indicator my actual plan speed?”

No. The “live” number on every modern router app (Deco, Eero, ASUS, Google Home, Netgear, UniFi) is current real-time traffic — not plan capacity. At idle it reads tiny because almost nothing is flowing. Plan capacity is a separate measurement that requires running an explicit speed test.

“I want to know which tier my specific ISP is overselling and what I should actually buy”

Every major US ISP has a tier their sales reps push and a tier most households actually need. The pushed tier is rarely the right one. Per-ISP patterns differ: Comcast pushes 1.2 Gbps, Spectrum pushes Ultra, AT&T pushes 5 Gbps Fiber. The right answer is usually two or three tiers below.

“I've talked to my ISP and they keep saying 'looks fine on our end' but it isn't”

Tier-1 support is script-driven and rewards closing tickets, not solving them. If your data is consistent and you've ruled out customer-side issues, the escalation path is well-defined: senior tech → retention → executive resolution, and external escalation via FCC informal complaint or state PUC when that stalls.