Fiber + DSL
CenturyLink / Quantum Fiber Speed Test
CenturyLink operates two very different products: legacy DSL under the CenturyLink name (typically 10–140 Mbps) and symmetric fiber marketed as Quantum Fiber (500 Mbps to multi-gig). Your speed test expectations should be set by which product serves your address — the difference is an order of magnitude.
What speeds should CenturyLink / Quantum Fiber deliver?
Quantum Fiber wired tests should show symmetric speeds close to plan — 500/500 or 940/940 Mbps on gigabit. CenturyLink DSL depends on distance from the equipment: nearby homes may see 100+ Mbps, distant ones under 20 Mbps, and that ceiling is physical, not fixable in-home.
On DSL, also watch ping and jitter — long copper runs and interleaving can push latency up, which affects calls and gaming more than raw bandwidth does.
Slow CenturyLink / Quantum Fiber speeds? Try this first
- 1Confirm your product: symmetric test results mean fiber; heavily asymmetric results with modest download mean DSL.
- 2DSL users: test with the modem plugged into the phone jack closest to where the line enters the house, with DSL filters on all other jacks.
- 3Quantum Fiber users can usually bypass the rented router with their own via the ONT's ethernet handoff.
- 4If DSL speeds dropped suddenly, ask CenturyLink to check the line — corroded outdoor wiring degrades sync rates and shows up after rain.
CenturyLink / Quantum Fiber speed test FAQ
What's the difference between CenturyLink and Quantum Fiber?
Same parent company, different networks: CenturyLink is the legacy DSL brand over copper phone lines; Quantum Fiber is the fiber-optic service with symmetric speeds. Quantum Fiber replaces DSL where it's built out.
Why is my CenturyLink DSL so slow?
DSL speed falls with distance from the provider's equipment — long or degraded copper lines physically can't carry high speeds. If your sync rate is the limit, only a fiber upgrade or different provider changes it.
What speeds does Quantum Fiber offer?
Symmetric plans typically at 500 Mbps and 940 Mbps, with multi-gig tiers in some markets. Wired speed tests should closely match the advertised numbers in both directions.