CenturyLink ISP service suddenly much slower

A year ago, the kind people in this forum helped me troubleshoot “not connected to the Internet” messages, and I ended up ditching CenturyLink’s outdated router to set up my own TP-Link Archer AX3000.

Service was good until about a month ago, when we noticed our CenturyLink fiber service again becoming slower and less reliable. Web pages load part way and stall, our Ethernet-wired Macs again report “no Internet connection,” and file downloads are much slower than we’re used to. The hardwired AppleTV stalls and buffers, and Apple Arcade games freeze.

Our plan includes 40mbps down and 20 up, and speed.me tests with wired Macs indicated that until now, we consistently approached those speeds with both the old router and the new.

We have no VPN or online backup services. The problem seems unrelated to the time of day.

Now it fluctuates wildly, sometimes jamming up so that speed tests stall and have to be reloaded, sometimes getting 4-5mbps, and a few minutes later jumping to 25 or 30. (but never up near 40mbps, as we’d been getting) Latency runs from near 100ms to over 200ms, while it used to be 10-30.

So, with the old router, service seemed to be fast, but frequently losing connection. (All or nothing!) Now, after a good year with the TP-Link, we occasionally lose connection, but mostly it’s just much, much slower.

I called CL and they said our connection/service looked OK to them. Of course, when I told them I was using my own router, they said I should call Archer.

I’ve restarted the router. When I’ve unplugged and reconnected the incoming line at the ONT outside the house, it seemed to get better for a few days. I find it more believable that they’re at fault, rather than my router spontaneously misfiring after a year of good service.

I’m suspicious that in this rapidly growing area of Northern Colorado, they’re outgrowing the infrastructure they laid down and are starting to have problems.

Is there a way I can test their incoming line, thus eliminating my router as a factor?

If not, what can I check on my router, other than restarting it?

What’s a good way to find out what’s going on? I’m not sure where to start.


At least the way it’s set up here (now Ziply, previously Frontier, previously Verizon FIOS) You can directly plug in a computer into the ONT instead of the ethernet cable to the router. Be aware that the computer will not be behind a firewall! The computer uses the DHCP service of the provider to get an IP address, likely the same that your router had on the WAN port.

At this point you can run speed and latency tests. If still bad, the problem is on the outside. It could be CenturyLink or something upstream from them.

If all is fine then the problem is with your router or other devices on your LAN. Divide and conquer! Certainly shut off your Wifi and test with only wired available – this would tell you if it is a Wifi problem.

I tried connecting to the ONT last week, but the MacBook appeared to not sense any connection. I’ll try again. I’m testing with wifi off… just the Ethernet cable.

I still have the old CenturyLink router and got the idea to reconnect it to see if the slowness is resolved. (its problem was losing net completely, not slowness) So, to get a baseline for the TP-Link router, I ran about 40 online speed tests and only two were noticeably slow (6.3 and 4.2mbps), while the rest were 35-38. Go figure! Hard to troubleshoot when the issue doesn’t reliably show up. But it is often enough for my wife to come complaining to me. :wink:

You said Ziply, previously Frontier, previously Verizon FIOS… We went from Verizon FIOS to Frontier when we lived in the Portland area a few years ago. Haven’t heard of Ziply.


Ziply Fiber is a new operation that took over the business from Frontier, May of 2020. I can’t tell any difference.

Does it happen more right at the top of the hour, or half past? If so I would suspect heavy loads from people going on Zoom meetings and so on. Can’t think of another easy way to test out “too many customers”.

Good idea. I’ll check it out. Thanks