Question Bizarre Connectivity Issue which makes zero sense

[Murphy's Lawyer]

First timer here and I hope you all can help with a bizarre situation I am having. I am not exactly a novice, but I am far from a networking expert. I know enough to be dangerous (that's what they all say).

Background: I have never had any issues connecting to the internet via ethernet or wifi. I am on one of Comcast's higher speed tiers. About 2 weeks ago during a zoom call, my coworkers told me that they could only hear every other word I said. I went to speedtest.net and the speeds were well below normal. This computer is connected via ethernet. I went into my equipment room and checked all of my connections. Everything was tightly connected. Then, the wi-fi began slowing down to ridiculously slow speeds. And then all connectivity died.

I have gone through multiple steps to try to correct this problem and I still cannot resolve it.

Here are my steps:

• Repositioned my network switches, router and cable modem.
• Bought new switches to replace the old ones.
• Had a networking resource come to my home to validate my ethernet connections. His theories were either I needed a new modem or have the cable company redo their cabling.
• Installed a new modem yesterday. Same issue persists.
• Had the cable company send a representative to my home. When we connected my computer directly into the router, it worked as it is supposed to with no degradation of speed. When plugged back into the router and switch, same issue persists. Cable tech recommended a new router.
• Installed a new router as part of my network tonight. Same issue persists.
• Plugged router, modem and switches into a different power outlet. Nothing, but the same.
• Plugged main computer directly into modem, works as expected. Plugged back into the switch/router, issues again. Reconnected computer directly into modem which is where I am now.

I do have some items in the equipment room which may be causing wifi interference, but it shouldn't be causing ethernet issues. As one friend of mine told me, "Your house is broken".

So, I have exhausted all avenues that I know other than moving all of my networking equipment out of the equipment room and into another room. I would prefer not to go down that route because everything worked previously. That would be my last ditch effort.

Any thoughts/theories/suggestions would be appreciated.

 

[Cyberat_88]

I am thinking dead networking cable between router & switch. Or extremely high electromagnetic interference requiring shielding. Location between router & switch.

 

[bill001g]

I am unclear why did you replace the router. I though you said if you plug directly into the router with a pc it is fine.
Do you have multiple routers, do you have a separate modem or does your router have both a modem and router in the same device.

The path needs to go

Modem---router---switch---device.

As you can see you have a couple places this can fail so I would start again by plugging in directly to the first box you can. If it is a modem you many time must power cycle the modem everytime you change what it plugged into it.
You then would slowly work out to see when the failure starts.

Make sure you unplug all other cables and I would even turn off the wifi just to be sure only your test machine is in the path.

Most modem or router/modem combo devices have logs and status displays. The logs might tell you something if you are lucky. The status display shows the signal strengths as well as error counts. You almost always have some small number of errors but a lot of uncorrectable errors means packet loss.

What you are describing generally is data loss even though if it is sever it will cause speedtest to run slow. Your best test to run ping command to say 8.8.8.8 or maybe to your router ip address. You almost never see issues to the router ip unless you are say on wifi, ethenet connected devices seldom get errors.

 

[Murphy's Lawyer]

I am unclear why did you replace the router. I though you said if you plug directly into the router with a pc it is fine.
Do you have multiple routers, do you have a separate modem or does your router have both a modem and router in the same device.

The path needs to go

Modem---router---switch---device.

As you can see you have a couple places this can fail so I would start again by plugging in directly to the first box you can. If it is a modem you many time must power cycle the modem everytime you change what it plugged into it.
You then would slowly work out to see when the failure starts.

Make sure you unplug all other cables and I would even turn off the wifi just to be sure only your test machine is in the path.

Most modem or router/modem combo devices have logs and status displays. The logs might tell you something if you are lucky. The status display shows the signal strengths as well as error counts. You almost always have some small number of errors but a lot of uncorrectable errors means packet loss.

What you are describing generally is data loss even though if it is sever it will cause speedtest to run slow. Your best test to run ping command to say 8.8.8.8 or maybe to your router ip address. You almost never see issues to the router ip unless you are say on wifi, ethenet connected devices seldom get errors.

I am unclear why did you replace the router. I though you said if you plug directly into the router with a pc it is fine.
Do you have multiple routers, do you have a separate modem or does your router have both a modem and router in the same device.

The path needs to go

Modem---router---switch---device.

As you can see you have a couple places this can fail so I would start again by plugging in directly to the first box you can. If it is a modem you many time must power cycle the modem everytime you change what it plugged into it.
You then would slowly work out to see when the failure starts.

Make sure you unplug all other cables and I would even turn off the wifi just to be sure only your test machine is in the path.

Most modem or router/modem combo devices have logs and status displays. The logs might tell you something if you are lucky. The status display shows the signal strengths as well as error counts. You almost always have some small number of errors but a lot of uncorrectable errors means packet loss.

What you are describing generally is data loss even though if it is sever it will cause speedtest to run slow. Your best test to run ping command to say 8.8.8.8 or maybe to your router ip address. You almost never see issues to the router ip unless you are say on wifi, ethenet connected devices seldom get errors.

I replaced the router trying to rule that out as the issue, yet the issue persists.

Also my connection is Modem>Router>Switch>Devices. To connect directly to the computer I have done Modem>Computer and Modem>Switch>Computer. When I connect directly, everything works perfectly. The issue is with the modem>router apparently no matter which router I use.

This morning I tried one other test: modem>router taking the switch out of the equation. The same issue persists no matter which router I use.

 

[bill001g]

Is the modem actually just a modem or is it also a router. If it can run wifi it is a modem/router combo device.

If it is a actual modem only then you should not hook a switch to it. There is only 1 device allowed at at time and that should be the wan port of your router.

It really is strange that you have the problem on 2 different routers. A router really isn't doing much it just uses NAT to share the single IP you get from the ISP with your internal devices. If you were to use some fancy firewall or QoS feature you can easily exceed the cpu in a router but if you run it with the default options all it really does is the NAT function and that is done in hardware and does not impact the cpu.

I would test ping to 8.8.8.8 and see if you see packet loss from your pc. Some routers also have the ability to run ping commands so it would be a interesting test to see if the router itself gets loss since it is directly plugged into the modem like you pc was with no issues.

 

[Murphy's Lawyer]

Is the modem actually just a modem or is it also a router. If it can run wifi it is a modem/router combo device.

If it is a actual modem only then you should not hook a switch to it. There is only 1 device allowed at at time and that should be the wan port of your router.

It really is strange that you have the problem on 2 different routers. A router really isn't doing much it just uses NAT to share the single IP you get from the ISP with your internal devices. If you were to use some fancy firewall or QoS feature you can easily exceed the cpu in a router but if you run it with the default options all it really does is the NAT function and that is done in hardware and does not impact the cpu.

I would test ping to 8.8.8.8 and see if you see packet loss from your pc. Some routers also have the ability to run ping commands so it would be a interesting test to see if the router itself gets loss since it is directly plugged into the modem like you pc was with no issues.

The modem is just a modem. It is not a combination unit. I was using a netgear nighthawk and now using a Motorola 88611 which is an approved model from my cable provider, Xfinity. The router I was using was a td-link x90 deco and now have switched to an eero Pro 6E.

I need to correct what I did because the lack of sleep over this is impacting what I want to say. I should not have stated I connected Modem>Switch>Computer. It was strictly taking the cable in my equipment room that is marked for my work computer and plugging that in directly into the modem. I was thinking I used the switch, but didn't. I know connecting directly to the switch would create chaos since my switch is unmanaged.

 

[Murphy's Lawyer]

I am thinking dead networking cable between router & switch. Or extremely high electromagnetic interference requiring shielding. Location between router & switch.

I am using brand new cables between the network and switch. That should not be an issue.

I am curious about the shielding. I have read things online that the Faraday cages are not that effective. Is there a different solution?

 

[bill001g]

It is extremely unlikely you have interference strong enough to affect ethernet cables. The problem tends to be the reverse where they worry about ethernet interfering with say medical equipment in the same room. Maybe if ethernet was in some factory where equipment that generate large magnetic fields. You never see it in a home install.

It does not really cause the type of issue you are reporting. It is easy to test just leave a ping run to the router IP. If data is being damaged you will get packet loss.

It is almost impossible to properly install shielded ethernet cables. Most people that buy it are installing it incorrect which actually increase the chance of interference.....but even double chance of zero is still zero .

To properly install it you must ground both ends of the shield in the cable. The ground must be separate from the power ground both for safety reasons and because the ground wire in the house may actually introduce interference from some appliance.
So you would have to spend money to have copper ground wires run to both ends and then connect it to a grounding rod. In something like a data center it is very common to have data grade ground running to the equipment racks but it is not something you ever see in a house.

It is highly unlikely that is your problem. Check your cables to be sure they are actually ethernet cables. Those flat cables do not have the proper twists in them and have wires way too thin to meet the standards. It is the wire size and twists in the wire that make ethernet almost immune to external interference.

 

[gggplaya]

What if you connect Modem-->Router-->Switch-->Single PC and disconnect everything else from the switch, so only your pc cable is connected?

If it works, then plug 1 cable in at a time.

 

[Cyberat_88]

Faraday Cages are effective but you don't have one, why not investigate if you need one ?
Do you have any equipment in the vicinity of this that can cause electromagnetic or microwave interference ?

 

[Murphy's Lawyer]

What if you connect Modem-->Router-->Switch-->Single PC and disconnect everything else from the switch, so only your pc cable is connected?

If it works, then plug 1 cable in at a time.

This was the winning solution!

I had a friend come over last night and we began to unplug everything out of the switches and replugged everything back in. We detected 4 ethernet connections that were creating the issue. These lines were not connected to anything active, but apparently creating enough issues to foul up the entire network. There could have been shorts in the cables, or something, that I guess will remain an unsolved mystery.

I appreciate everyone chiming in with responses and potential solutions. Trying to resolve bizarre networking issues is like the trying to find the needle in the haystack when the known obvious troubleshooting steps don't work. You would have thought the networking guy I had over on Monday would have been able to resolve this.

Anyway again thank you all for your help.