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

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Clearly, you're connected. If you wait until you can't get online to worry about this kind of thing -- as most of my friends who have my number on their speed dial do -- you'd be in a pickle. You can't use the Internet to troubleshoot or look for instructions, especially when there's no cell signal.

And I've had many experiences calling the Internet service provider for help with being disconnected only to have an automated message pointing me to a specific troubleshooting webpage. If I could do that, I wouldn't have called in the first place.

So, it's good to be well-prepared to avoid that catch-22 scenario.

Let's dive in!

Wi-Fi and the Internet are two different things -- you're reading about the former. This post on Wi-Fi dropping and local connection issues will help tackle the latter.

Dong's note: I first published this post on January 18, 2019, and last updated it on March 3, 2023, 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 (a modem, in the photo above) 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, but all have a broadband terminal device -- likely a Cable modem or a Fiber-optic ONT -- and a router. Sometimes, those two are combined in a single hardware box called a residential gateway.

Which hardware is your Internet setup? That's the first thing you should know. The table below gives you a quick idea.

Cable Modem vs Fiber optic ONT MSI RadiX AX6600 Router NVG578LX GPON Gateway
Device TypeBroadband Terminal Device
(Cable Modem/Fiber-optic ONT)
Wi-Fi Router
(including the primary unit of a Wi-Fi mesh system)
Internet-Related RoleBrings Internet to your home
(via the service line)
Brings the Internet to your devices
(via network cables or Wi-Fi)
Local RoleConnect to a wide area network (WAN) -- the InternetCreates a local area network (LAN) networkBoth
IP Address
Maintain a wide area network (WAN) public IP addressAssigns and manages LAN IP addresses to local devicesBoth
Home network basics: Terminal device vs router. A residential gateway includes both in a single hardware box.

No matter if you have an ONT, a modem, or a gateway, 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 o the hardware involved.

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 (like or a service (such as Netflix), the first thing to do is try a few different ones to see if they work.

Many times, the specific party you want to access is unavailable. And that has nothing to do with your home network or broadband connection. In this case, you can only wait it out.

Your device’s Wi-Fi might be turned off

That's right. You might have accidentally turned off the Wi-Fi on the router or the device you're using.

This issue is common in laptops where you might accidentally switch on the Airplane mode. It applies to some media streamers and IoT devices, such as printers. These tend to have a button to turn the Wi-Fi function on or off.

Some routers also have a similar on/off switch for the Wi-Fi function. There's no Wi-Fi if you turn it off. If so, turn it back on!

Which Wi-Fi network you’re using?

This can also be a frustrating case. Your device must be connected 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 ensure 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

If you have taken care of the housekeeping above and the issue persists, it's time to do some digging to locate the problem.

Two things to keep in mind:

  • Can you connect a device to your Wi-Fi network? If you can't, or the Wi-Fi 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 cannot access the Internet, the issue is likely at the broadband terminal device.

In any case, you can always start with your Cable modem or Fiber-optic ONT. It doesn't hurt.

Cable Modem vs Fiber ONT
Terminal devices 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 an AT&T Fiber-optic ONT.

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

Your terminal device is the actual hardware piece that connects your home to the Internet. There are many terminal types, but the Cable modem and Fiber-optic ONT are the most popular.

These two are slightly different -- more in this post on cable modem vs Fibe-optic ONT -- but no matter what type of terminal device you use, you need to ensure two things:

  1. The device has a good connection to your Wi-Fi router. And
  2. It has a live link to the Internet.

The first item is to check and ensure that the network cable connecting the two is intact and securely plugged in on both ends -- it goes into the WAN port of the router. Use a new cable if need be.

The second item -- the terminal device's live Internet connection -- won't take long, either, but it requires some attention.

How to handle a Cable modem or a Fiber-optic ONT

The tabs below contain detailed steps to check the Internet signal on a Cable modem or a Fiber-optic ONT.

What to do with a modem

All modems have a broadband status light, a.k.a "signal" or "sync" light.

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

Broadband Internet Troubleshooting: The MB8600 Cable Modem 9ARRIS SURFboard S33 Modem Status Light
Here are two modems in action. The first, Motorola MB8600, has a traditional design with a good set of status lights -- the broadband light is the second from the bottom. The other, the ARRIS S33, is one with just a single color-changing 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.

Here are what you can do at the modem if the broadband status light is off or shows that it has no signal from the provider:

  • Check the broadband status light. It must show the correct color. In a traditional modem, the broadband light must be solid (green, blue, or white). If it's not lid, red, or flashing erratically, ensure the service cable is intact and securely attached to the device. Then, you should:
    • give the modem a restart, then wait a few minutes for it to boot up fully. Often that fixes the problem.
    • reconnect the service line: Unplug it from the modem and re-connect it tightly.

If all that doesn't fix the issue, then:

  • Check to ensure there's no outage in the area (or you can check that first before checking the modem.) If there's no outage, then:
  • Call your Internet provider. At this point, there's nothing you can do. Tell the customer support agent you have no Internet signal at the modem. They'll check on their end and fix the issues. Sometimes, if your modem no longer works or is supported, they will tell you to get a replacement.

If your modem appears fine, you might want to also re-connect both ends of the network cable that link the modem and your router. Or even replace it to make sure.

What to do with a Fiber-optic ONT

A Fiber-optic ONT is more simple than a modem. 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 the three status lights that are currently on (from the 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, ensure the Ethernet shows the connection status between the ONT and the router's WAN port is also in good shape.

There are three things you can do to troubleshoot an ONT -- you can do one or all three at a time but be gentle with the wires involved:

  • Restart the ONT itself -- unplug it from power for about 10 seconds and plug it back in. Then give it a few minutes to fully boot up.
  • Re-connect the Fiber-optic service line -- remove it from the ONT and then re-connect it.
  • Re-connect the network cable connecting the ONT and your router. Sometimes you might want to use a different cable.

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

If that doesn't fix the issue -- the broadband light is still off or shows disconnected status -- it's time to call the provider to report the problem. There's nothing else you can do.

If your terminal device:

  • shows a live Internet connection, and
  • its connected wires are in good shape,

yet, you still have connection issues on your device, then it's time to check your Wi-Fi router or the router unit of your mesh system.

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 take:

  • 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 each band (5GHz, 2.4GHz, or 6GHz). 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).
VendorFriendlyΒ URL
(Internet connection required)
Default IPUsernamePassword
AT&T Gatewayn/a192.168.1.254n/aAccess code printed 
on the hardware unit
(Xfinity) Gateway
Access code printed 
on the hardware unit
(printed on hardware)
Most Cable ModemsN/A192.168.100.1n/aadmin
Default Interface access address popular of routers/gateways/modems by vendors.

In case 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.

You should describe exactly what has happened instead of what you think has occurred, the consequences of the problem, or how you feel about what happened.

In other words, don't give the person on the other end stuff without 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 status lights, etc.

It's also helpful to take and share photos of the error messages and the device itself. 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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39 thoughts on “Broadband Internet Troubleshooting: Steps to Fix a Cable or Fiber-optic Connection”

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  1. Hi Don’t. Can you please help me? I have been given a really old PC but it’s in good condition. It was working but now I can’t get it started again. The lights on the modem are working except for one which is orange, the rest are yellow.
    Many thanks

  2. Thank you as always for all the information you provide. Have been following you since you were at Cnet and still have your original videos of wiring a home network with the specific tools you use.
    If a router company no longer is sending out updates for a specific router would that suggest it’s time for a new router?
    Have been reading and re-reading your reviews of Wi-Fi 6E ones as mine no longer seems to receive these updates.

    • Firmware updates are not always good, George. They are necessary in case the hardware has vulnerabilities. If there’s no vulnerability and the vendor doesn’t want to add more features, then there’s no update. In short, you shouldn’t use updates as the only indicator of whether the hardware is good or bad or still supported. So this is case by case. Most of the time, no update is a good thing.

      In many ways, firmware updates to routers are like recalls to cars.

  3. Is it possible to have equipment issues with every device connected to a specific internet connection? As in, every phone, tablet, laptop, Chromebook, desktop that has ever been connected to this internet having issues with memory, losing files, showing no signal when there is signal or showing there is signal when there is no signal? Even printers do it. Brand new, old, Android or Iphone, Chrome OS and Windows and Linux. We have had issues wih my daughter’s internet for two years. From Nov. 2019 until she finally gave up in 2021, 30 techs had been to her home and all said there was nothing they could find and they reran wiring and all of that. Shes had her gateway swapped like 5 times as well. She is computer literate, never had issues before and we just have no idea what to do.
    If there is no common machine OS that is experiencing the issues, but all of them, what should we do?

    • Technically, Beth, it is. It’s like if you put a filter on the water intake pipe of your home, all faucets within the house will be affected.

      However, considering what you described, it’s likely your daughter’s devices (or her online accounts) have been infected with something. I’d recommend getting help from a local trusted professional.

  4. I just signed up for optimum 2.5gb internet. They provide this device which I am now finding out is limited to what I can do with it. There is no GUI to login to configure it. So I cannot add my own AP on top since I cannot shut off the Wi-Fi it comes with. You can use a DOCSIS 3.1 Modem but they all have COAX input and the do not use COAX at all. So I am in a pickle and don’t know what to do. Any advice is helpful on my options. I do want to use my own devices.

  5. 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?

  6. 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?

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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!!

  17. 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.

  18. 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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