Recurrent internet drops at 10:00

[Smasher85]

Talked to the ISP, and they won’t file a fault report unless I can recreate the issue with my computer connected directly to the fiber modem. Since they won’t forward me to a technician, there’s no point in asking support questions like why the DHCP lease time is set to 600 ms (and whether that’s even a problem), because they simply don’t know.

The downside is that connecting my computer directly to the modem means no other device will have internet access, which is a tough sell in this household.

If I connect the modem directly to my computer, can I then share the connection with the rest of the network? If so, how? I guess I might need a secondary network card, maybe I even have an old one lying around from the early 2000s.

 

[dave14305]

If the PC works, try cloning the PC’s MAC address on the router’s WAN page and reboot.

 

[Smasher85]

That’s a good idea, I’ll try that later. I’ve just connected my computer directly to the modem again to see if I can re-create the problem. Usually, the issue only occurs around 10–11, but yesterday I let the PowerShell script run more or less all day and I had a lot more problems. So now I’m running the same script, but with the computer connected directly to the modem, to see if that changes anything.

 

[bluzfanmr1]

Shot in the dark here. I have fiber and to use the modem directly, I have to set a VID of 201 (Brightspeed Fiber) on the IPTV tab for internet to work. It reminds me of the issues I had until I realized I had to do this but like I said, maybe a shot in the dark.

 

[Smasher85]

Thanks, I’ll put it on my list.

I bought a new router today, a TP-Link BE230, just to test if that might solve anything. I set it up the same way as the others, but with one difference: I chose to clone the MAC address of my computer, just like @dave14305 suggested.

After having multiple issues earlier today, I haven’t had any since installing the new router, but we’ll see. My old Netgear router also failed me with similar problems, though it already had known defects (including internet connection issues), so it’s hard to know what that really means.

I’ll let the new router handle the full extent of my network for a couple of days. If it doesn’t fail me, I’ll send in the Asus router for service.

I went with TP-Link because it’s unclear how much hardware different Asus routers actually share, and I wanted a totally different brand to see if it works better in my system. I know that mixing different network brands used to be a problem, but maybe not anymore?

​

 

[Smasher85]

The issue occurred again and lasted for 20 minutes, as it usually does. So the new router was not the solution, which is not really a surprise.

BUT a friend of mine happens to have the exact same problem with the same ISP, even though he lives in another city. He suggested pressing F5 (refresh in Edge) multiple times while trying to load the webpage, and surprisingly, it worked. Once the page loads successfully, I can browse its subpages without any issues.

My guess is that the connection to the DNS sometimes fails for periods of around 20 minutes. It’s probably being blocked on a higher level where we can’t affect it. When the call succeeds, the browser stores the DNS and uses it on subpages. It doesn’t matter if we change to a different DNS, the issue still occurs the same.

I haven’t tried it myself, but apparently, it’s also possible to access the webpage directly via its IP without hitting F5 during a problematic period.

Why it works when connecting the cable directly to the computer I can’t say. Maybe the problem would actually appear there too if I left the computer connected to the router all the time.

So, yet another piece to the puzzle, so what now?

 

[tgl]

Does the restart-the-router hack still fix the problem when using this replacement router?

Also, it's not clear to me whether you are relying on any DNS caching/forwarding mechanism in the router(s), or just letting clients send requests out to the external DNS server. One thing that might clarify this is to look at a client's internet connection details, and see whether it reports the DNS server address as being the router's LAN address or the external server's.

 

[Smasher85]

I will try restarting the new router when the problem comes back. I haven’t changed the factory settings except for the passwords and SSID, so the client uses the router’s URL for DNS, and the router then forwards it to the DNS servers provided by the ISP.

 

[Tech9]

And you are absolutely positively definitely sure there is no forgotten rogue DHCP server running on one of your devices?

 

[Smasher85]

There is only one router and one fiber modem in the network, along with four switches. I have never configured any computer or device to handle DHCP.

I will try to downsize the network to just the absolute necessities, hopefully only a handful of devices. I will also try replacing the cable between the router and the modem.

 

[degrub]

Does the ISP also provide a free router or only the ONT ?
If they do, get it and run it for a while.

 

[Smasher85]

Does the ISP also provide a free router or only the ONT ?
If they do, get it and run it for a while.

No, they don’t. There’s only a fiber modem on the wall from the local fiber network provider. I’m thinking I could connect my main computer directly to the fiber modem, and then connect the rest of the network, including the router, to another LAN port on the modem. This way I will not block internet from others in the house during test period.

 

[Tech9]

This Modem with few LAN ports... are you sure it's not a Gateway (Router) device?

 

[degrub]

Maybe upload a picture of the "modem" brand name and model number ? With available ports shown as well, please .

 

[Tech9]

And perhaps this ISP device has logs as well...?

 

[Smasher85]

It's not really a modem but a fiber service termination unit (CTS JES-3106). I misunderstood its function, the ports are probably preconfigured by the provider for specific services like Internet, IPTV, or IP phone, not for plugging in multiple Internet networks.

 

[Tech9]

It's a managed CPE switch with quite a few features, but I guess you have no access to this device configuration. Anyway... this connectivity issue at specific time of the day is either ISP related and everyone around using the same ISP will have the same experience and report the same issue, either one of your clients related issue because you ruled out the router as a cause.

And you are absolutely positively definitely sure you don't have a network loop somewhere between your many switches?

 

[Smasher85]

I stripped down the network yesterday. I took back the Asus GT-AX6000 router, turned off Wi-Fi, and removed all but 4–5 wired devices. Some of them were connected directly to the router instead of through the switch (which connects to the router). So far, no problems, but it’s too early to say if this is really working.

There is only 1 DHCP service in the entire network.

The ISP is probably using CGNAT. Could it be that the ports are depleted? Should the ISP be able to check if this is actually the problem?

 

[ColinTaylor]

The ISP is probably using CGNAT. Could it be that the ports are depleted? Should the ISP be able to check if this is actually the problem?

Depleted? What do you mean by this?

 

[Smasher85]

Depleted? What do you mean by this?

I'm far from an expert on the subject, obviously, but from what I understand a CGNAT means that several users share the same public IP address. To allow communication with services outside the LAN, the CGNAT assigns different ports to each connection. Since the number of ports is limited, if all of them are in use new connections can be rejected. However, ports are released over time, so refreshing a page (like pressing F5 in a browser) may eventually work once a port becomes available?