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Broadband Internet Troubleshooting: Steps to Fix a Fiber-optic or Cable Connection

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We often only care about broadband Internet troubleshooting when there’s no connection. But of course! There’s no need to do anything when all is well.

However, we can’t search the Internet to troubleshoot connection-related issues when, well, there’s no Internet. And the irony is when you call an ISP’s tech support line, chances are you’ll have to go through an automated section that advises you to visit the troubleshooting webpage.

So, kudos to you for reading this right now, when you’re still connected. It’s good to be well-prepared.

Before continuing, make sure you understand that Wi-Fi and Internet are two different things.

Aso, this post focuses mostly on the Internet connection. If you want to troubleshoot your Wi-Fi connections, check out this post on Wi-Fi dropping and connection issues.

Dong’s note: I first published this post on Jan 18, 2019, and last updated it on April 17, 2022, to add more relevant information.

Broadband Internet and Wi-Fi: Netgear CM600 Cable Modem
Broadband Internet Troubleshooting: A typical Wi-Fi network setup: A router connects to a terminal device (in this photo, that’s a modem) via its WAN (Internet) network port. Note the service line (white) attached to the terminal device’s service port — make sure the two are securely connected.

Broadband Internet Troubleshooting: Four simple steps

Every network is different. Most importantly, you need to know if yours consists of a terminal service and a router or a gateway. The latter is a device with a terminal device and a router inside a single hardware box.

To find out which is which, you can consult this post on home networking hardware.

But with all of them, you can apply these steps when you don’t have a Wi-Fi connection or have no Internet access. Often, the issue is minor and requires as little as a restart of the router or modem.

1. Take care of the basics

These are basic things you should do first before anything else.

The service (or website) might be unavailable

If you can’t go to a particular website or a service, the first thing to do is try a few different ones to see if they work.

That’s because many times, the specific site or service is unavailable. And that has nothing to do with your home network or broadband connection. The same idea applies when you can’t access Netflix but can still stream from YouTube.

In this case, all you can do is wait it out or call the particular service provider to find out more.

Your device’s Wi-Fi might be turned off

Make sure you haven’t accidentally turned off the Wi-Fi on the device.

This issue is common in laptops where you might switch on the Airplane mode by accident. It applies to some media streamers and IoT devices, such as printers.

Also, some routers have an on/off switch for the Wi-Fi function — make sure it’s in the on position.

Which Wi-Fi network you’re using?

That’s right. Ensure your device connects to the correct Wi-Fi network (and not one of your neighbors, for example.)

Connecting to the wrong Wi-Fi network will cause local tasks — such as network printing or file sharing — to fail.

Most importantly, you’d be troubleshooting the wrong network.

Are the cables intact and plugged in securely?

This issue can be relatively rare but it doesn’t hurt to make sure all the cables and wires are plugged in properly and intact — not cut, broken, or chewed up by pets.

All hardware devices (router, modem, ONT, gateway, switches, etc.) must be plugged into power and turned on. At the very least, you should see some lights coming out of them.

Wi Fi 6E Symbol
Broadband Internet Troubleshooting: If you can see your Wi-Fi network being broadcast, chances are your router is working well.

2. Figure out where the issue is

With the housekeeping taken care of, it’s time to find out where the problem is.

Two things to keep in mind:

  • Can you connect to your Wi-Fi network? If you can’t, or your network is unavailable — you don’t see the Wi-Fi name on your phone — the problem is likely at the Wi-Fi router.
  • If you can connect to your Wi-Fi network but you cannot access the Internet, then the issue is likely at the terminal device — chances are that’s the Cable modem or Fiber-optic ONT.

In any case, you can always start with the modem/ONT.

Cable Modem vs Fiber ONT
Terminal devices: These devices tend to come in different shapes and sizes depending on your service provider and service. But it’s important to know which you’re using. In the picture: a Cable modem (top) and a Fiber-optic ONT.

3. Broadband Internet troubleshooting: How to check the terminal device.

Your terminal device is your connection to the Internet. It needs to be in good shape. There are many types of terminal devices but the Cable modem and Fiber-optic ONT are the most popular.

If you use a modem, things are slightly different from when you use an ONT. But the idea is the same no matter what type of terminal device you use:

  • Make sure the device has a live connection to the Internet. And
  • It has a good connection to your Wi-FI router. (Applicable only when you use a separate router and not a gateway)

The detailed steps below apply when you use a Cable modem or a Fiber-optic ONT.

What to do with a modem

No matter what modem you use, it always has a broadband status light.

In most modems, such as the Motorola MB8600 below, this light tends to have a shape or a label that suggests that it has something to do with the Internet. Often it resembles a little globe or the letter E.

Broadband Internet Troubleshooting: The MB8600 Cable Modem 9ARRIS SURFboard S33 Modem Status Light
Here are two modems in action. One is a traditional design with a good set of status lights. The other is one with just a single status light which can be confusing in troubleshooting.

However, some modems, such as the ARRIS SURFboard S33, come with a single light that changes color to show the status. In this case, you must remember what color indicates it has no Internet connection.

In any case, here is what you can do at the modem.

  • Give the modem a restart, then wait a few minutes for it to boot up fully. Often that fixes the problem. (If the modem is hard to reach, you can do this via its web interface. Almost all modems use the default IP address.)
  • Reset the service line: Undo it from the modem and re-connect it back in tightly.
  • Check the broadband status light. It must show the correct color. In a traditional modem, the broadband light needs to be solid (green, blue, or white). If it’s off, red, or flashing erratically, ensure the service cable is intact and securely attached to the device.

If that doesn’t fix the issue, check to ensure there’s no outage in the area.

If nothing works and there’s no outage, it’s time to call your provider. At this point, there’s nothing you can do. Tell the customer support agent that you have no Internet signal at the modem. They’ll know what to do.

What to do with a Fiber-optic ONT

A Fiber-optic ONT is even more simple than a modem, but it also has a broadband light often labeled as PON or has a star symbol.

Sonic 10Gbps Fiber optic ONT
Here’s a Sonic 10Gbps Fiber-optic ONT in action. Note their status lights that are currently on, from left: the 10Gbps Ethernet connection to the router (white cable), the broadband light (green cable), and the power light (black cable).
This particular ONT in the photo can also deliver a second Gigabit connection (not in use) and two phone lines (not in use).

This light has to be solid. After that, make sure the Ethernet shows the connection status between the ONT and a router’s WAN port is also in good shape.

There are two things you can do to troubleshoot an ONT:

  • Restart the ONT itself — unplug it from power and plug it back in.
  • Reset the Fiber-optic service line — remove it from the ONT and then re-connect it.

In the photos above, the black cable is for power, and the green one is the service line.

If that doesn’t fix the issue, it’s time to call the provider.

4. Wi-Fi issues: What to do at the router

There are a couple of things you can do with the router. There are simple and advanced steps.

Simple things you can do with a router

These are steps anyone can do.

  • Give the router a restart — unplug it from power, wait for 10 seconds or so, then plug it back in. Now give it a few minutes to boot up fully. That might fix the issue.
  • Ensure the router’s Wi-Fi function is not turned off — many routers have an on/off switch for Wi-Fi. Generally, the router has a status light for its bands (5GHz and 2.4GHz). These lights need to be on.

Advanced steps in working with a router

These are general steps for advanced users or those comfortable with computers.

  • Access the router’s web interface. Try updating its firmware to the latest.
  • Access the router’s interface gain. This time, back up its settings, then reset it — yes, I do mean reset — and set up your network from scratch (or restore it from the backup file).
VendorFriendly URLDefault IPUsernamePassword
AT&T Gatewayn/a192.168.1.254n/aAccess code printed 
on the hardware unit
(Xfinity) Gateway
Access code printed 
on the hardware unit
Most Cable ModemsN/A192.168.100.1n/aadmin
Default Interface access address popular of routers/gateways/modems by vendors.

If you can’t access the interface or don’t know how to reset it using the interface, you can reset it via the reset button. If all that doesn’t solve the problem, it’s time to get a new router or professional help.

Broadband Internet troubleshooting: How to get help

When you call for help, the person on the other end will try to troubleshoot the problem.

It would help if you told them exactly what has happened instead of what you think has happened or how you feel about what happened. Also, describe the issue instead of its consequences.

In other words, don’t give the person on the other end stuff that has no technical information. Examples: “I can’t get online,” “my internet doesn’t work,” “my computer doesn’t work,” “my Wi-Fi is not working,” etc.

Instead, be descriptive and explain exactly what happens. Such as, when I go to an XYZ website, I get an ABC message. Or give the person the error message or what you see on the hardware, such as the statutes, lights, etc.

It’s also helpful to take and share photos of the error messages and the device’s status lights. Visual is always useful when it comes to troubleshooting.

The takeaway

Internet, like all things in tech, is technical and dry. The best way to deal with them is to understand how things work. Getting frustrated or taking things personally won’t help.

Here’s the silver lining: If you pay attention and follow the instructions, it’s almost a guarantee that you can fix it. For this reason, dealing with machines is almost always easier than dealing with the emotions of our kind. I speak from experience.

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31 thoughts on “Broadband Internet Troubleshooting: Steps to Fix a Fiber-optic or Cable Connection”

  1. Dong, love the site. Very useful information, guidance and reviews. I have a TP Link A10 and for some reason the connection died one afternoon and lost IP connection completely. After diagnosing and isolating the issue, the IP issue was with the router as there was no IP listed in the status (blank). Called TP Link SUpport and they suggested to do a MAC Clone with my computer. Im wondering why this worked and restored my TP LInk router and was able to get an internet addressed and connection ultimately? Can you explain that behavior?

  2. Hi Do g
    As always great info. I just had a situation where the tech cables the ONT to router using cat 3 cable (10baseT). So while I would get 300-800 meg it would not be sustainable.
    Especially with zoom calls it would drop out all the time.
    Thankful a young new tech called for help and the master tech fissured it out because the young tech was doing extra work that an experienced tech would have refused to do.
    so very thankful for youth!
    The only way I can figure out how to test for this is a 3-5 minute line saturation. Any thoughts on how to do this since a normal speed test is short?

  3. I’m not sure how I found this blog, but maybe I can find the help and direction I need. I have xfinity internet (5ghz), and 3 computers (Imac desktop, and 2 macbook pro’s) that use the internet. Only 2 computers, at the most, are online at the same time. My Imac desktop (25 ft away in another room) connects wonderfully. My macbook pro also works great as to speed and connectivity where ever I go in the house. However, my wife’s macbook pro (the same model as mine) will only connect if she is within 2-3 feet of the router. Once she moves further away, it loses it’s connection and tells me I have to move closer to the router. This suggests to me that the issue must be with her computer, because my computers connect well and don’t drop their connections, even at further distances. I’ve tried to get help from a online service, and they can’t figure it out…..besides suggesting a full reinstall of the operating system (OS 10.12.6) My laptop has the same OS as my wife’s. Any suggestions on what direction to head to help my wife’s computer be able to move further away from the router and not have the connection dropped? Thanks for your time, effort, and quick reply in advance. Any help is appreciated.

  4. One additional somewhat more advanced debugging technique esp. if you have your own cable modem separate from your router is that, by convention, almost all of the cable modem man’f make accessible an internal web server in the cable modem and have given it the same IP address, namely So if you can get to your router successfully from a PC or laptop (i.e., your router is up and working), trying to open a web browser connection to and then logging into the cable modem web server. Some cable modem web servers require a user id and/or password, and each vendor has their own default which you can usually search when your connection is up (so do this before you need to). Once logged in, there is usually a wealth of information available about the state of the modem, error logs, channel connection status, etc. One very useful feature on most of these is the ability to reboot your cable modem remotely, esp. useful if your cable modem is inconveniently located like on a different floor of your home from your PC. The default userid/password isn’t a terribly vulnerable security hole since the cable modem is on a non-routable private address so it can only be accessed from on your LAN, but if you want even mode security you can typically change it to something more private as well.

  5. Our entire community has a dedicated fiber ISP. My neighbors & I can connect to our ONT’s w/older AC-type routers [via ethernet cable to the router WAN], right “out of the box”, without any special setup or configuration. But we are unable to connect ANY newer AX-type routers. ASUS, Netgear & TP-Link service techs have been unable to assist us. Is there any difference in the AX router WAN [input] circuits?

    • That doesn’t make sense, Larry. If the connection works with an AC router, it will work with an AX router. What exactly did you mean by “unable to connect,” by the way? Because clearly, you *can* connect a network cable into the ports of the two parties. It’s physics.

      • I know it doesn’t make “sense”, but we can [repeatedly] connect new or old AC routers to our ONT’s and get to the internet, while we are unable to connect [get internet] w/three brand new AX routers. I thought there might be something different about the input/WAN circuits on the AX routers. The router techs – and our ISP techs are unable to assist us.
        Currently, there are many AC routers on the market. But I assume this will not [soon?] be the case.

        • That’s super odd, Larry. You need to check the interface of the AX router to see what the error of the WAN connection is. Also, try these:

          1. Restart the ONT and the AX router after the setup. In that order.
          2. Copy the MAC address of the AC router that worked on the AX router that didn’t. Use the latter’s MAC clone.

          And no, AC routers will still be on the market for years to come. AC is not going away anytime soon.

          • Thanks for trying to help us Dong. Unfortunately, power cycling and “MAC spoofing” do not help. It is a very interesting problem. All AC-type routers [and even desktop/laptop PC’s w/AC cards] will readily connect to the ISP ONT. Three brands of AX routers will not. [ASUS, TP-Link & Netgear]
            To increase wifi coverage in my home I have connected a new Netgear [RAX50] router to a LAN port from an older AC router. But I would prefer not having to run [2] routers.

  6. Very good article for the first steps but i was hoping there would be information about actually analyzing the status and event log. The specific (only) service provider here stock answer is that the problem is not there’s, even though multiple users report same problems. I don’t know what the boundaries are for Freq Pwr SNR or what some of the event log entries actually mean. Do you have that info posted or can point me to the correct place to find it? Thanks so much for sharing all this information

    • That’s specific to an Internet provider, Emma. Generally, when it comes to that, you need to contact the vendor or a professional.

  7. So I tried putting the TP Link M9plus into AP mode and hang it off my Linksys 1900AC+. I noted the same drops. So I hardwired to the Linksys
    router and ran ping tests. Same thing happened. I believe the COmcast Cable modem is the problem and will have to get that swapped out.

    I may put the Deco M9 back as the main router again instead of AP mode..

    • And a few days later, the drops have stopped.. I will probably remove the Linksys as the router and put the Deco M9 back at Router/Mesh to keep it
      simple. Comcast must have fixed their issue.

  8. Hello Dong! Great advice as usual. I’ve had intermittent issues with my internet. Switched modem and router and problem still remains. Had spectrum out to have a look and they confirmed everything was fine on their end. Very frustrating until I moved the modem away from the router and my Verizon cell booster. Is it possible these were interfering with the signal somehow? Much better since I moved it.

    • Definitely, David. Don’t use any “booster” devices (Wi-Fi or Cell). They are no good. Most cell phone now has the Wi-Fi calling feature anyway.

  9. Hey Dong, has anyone developed a system / device or whatever, that can allow you to access the internet, when your primary internet goes down? Kind of like a “Backup” internet of sorts?

    I thought about this the other day, when my internet went down and I could not view my wifi cameras.

      • Hey Dong, thanks for the reply…..Have you done a article on this, on this platform yet? It would be very educational… (hint hint)

        • Not yet on this feature specifically, David. But it’s relatively straight-forward. You need two Internet sources (Cable + DSL or cellular, for example), then you can set them up as load-balancing (if the two are of similar speeds) or failsafe.

  10. Hi Dong,

    Very impressed with your site and your advice!

    Would you say in general that you get better/stronger results using your router’s dual-band smart connect rather than keeping the 2.4 and 5 G networks separate (I’m thinking about the Asus RT-AX3000 router)? Are there other settings you automatically change from the default settings that you would recommend for better performance?


    • Thanks, Alan. And no, the Smart Connect is just a matter of convenience. It has nothing to do with signal strength. The only benefit is it allows a device to automatically switch to the 2.4GHz band when the 5GHz one range, which is shorter, diminishes. So it might give you the elusion of signal strength and longer range at the expense of not being able to make sure your device will connect to the 5GHz band, which is faster at a close range.

  11. Doug
    A question on bouncing a router which I do weekly via a mechanical timer.
    Upon reboot, my TCL tv which is an Ethernet connect direct to the router loses its Internet connection and I have to reset the network connection on the TCL Roku device to regain internet access. Any suggestions?
    Thanks in advance.

    • I wouldn’t do that using a mechanical timer, Jerry. If the router has a restart on schedule feature, use it (that’s the only time when the term “bounce” is correct by the way). If not, just manually do it when you feel like or when it’s convenient, or when need be. I’d try restarting each of those devices manually, one at a time, to see if the disconnection happens. You’ll then find out where the problem is, the router or the TV. In any case, make sure you get their firmware to the latest.

  12. I am so happy I found your blog and I absolutely love your information about the internet and wi-fi trouble shooting.I liked and it is wonderful to know about so many things that are useful for all of us! Thanks a lot for this amazing blog!!

  13. This article provides us information regarding internet and wi-fi trouble shooting. I loved the way they have researched and presented it infront of us. Here you will get to know in detail about the topic which are in demand. I enjoyed alot while reading this article and would recommend other.

  14. I have been having that problem intermittently for the last couple of months and Comcast has been unable to fix it. I was thinking maybe it was my computer. Thank you so much for writing this article. I printed it out and will try to follow it.
    Thank you for your help-you have helped me before and I really appreciate it!

    Best, Marsha


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