8 Port Switch Stopped Working

dlister70

New Around Here
I have a Linksys CM3024 cable modem with XFinity internet. That goes into an Eero wireless router. Then out of the router into an 8 port switch to run all the wired components (my PCs, network printer, PlayStation 3 & 4, etc.)

This has worked for over a decade with a basic unmanaged D Link switch. One day it didn’t work anymore. I figured that the switch had more than lived it’s life so I bought a cheap TP-Link TL-SG1008D for like $25 and replaced the D Link. Everything was fine for 3 months and then last night it stopped working again.

I reset everything and tried a different ethernet cable, but it just wouldn’t work. I was annoyed that it only lasted 3 months but figured that the cheap switch just died too.

I bought a Netgear GS108 today and hooked everything up, but it still doesn’t work. So maybe the switch never was the issue? The port lights are coming on and blinking, but none of the devices are connecting.

Wireless works, and if I plug my computer ethernet cord directly into the Eero, it works too. So I’m getting service from the Eero port. But when I run it into the switch, it doesn't seem to be going anywhere after that. PCs, PlayStations, printer, nothing is connected to the Internet.

I am at a loss for what to even look at. Any advice would be appreciated. I thought that it must be a hardware problem with the switch if every component hooked into it stops working at once, but hooking up a new one and getting the same results seems to contradict that.
 

Tech Junky

Very Senior Member
So, a switch doesn't usually have an issue if you replace one but, the CM / Eero might. Did you reboot everything in line with the host <> internet?

Seems a bit odd that you've gone through 3 switches with the same issue but 3 different vendors.

Is the issue that replacing the switch you don't get an IP?

Can you configure 2 devices with static IP's w/o a gateway and can they see each other / move data between them?

Did you leave the VLAN configured as 1 (default)?

Did you do a hard reset if possible to purge any configuration information from the new switches?
 

dlister70

New Around Here
If I power cycle the Netgear switch, it will give me an IP on my computer of 192.168.4.70, but when I try to use a browser I get a DNS error for every website. My DNS servers are showing as 75.75.75.75 and 75.75.76.76

I rebooted the cable modem, router, and switch when the TP-Link stopped working last night, but I only rebooted the router today when I installed the new Netgear switch. My wife is on a zoom call at the moment, so I don’t want to power cycle the CM right now, but I can try that later and perhaps get an easy fix. I figured that the cable modem was doing it‘s part since I had wireless and wired from the back of the Eero, but I’m clearly out of my depth.

I didn’t change any default configurations In regards to VLAN.

I have not set up two machines with static IP. I just googled how to set a static IP in windows 10, and tried to do so, but i got an error saying “can’t save IP settings. Check one or more setting and try again.”

I do not see a paper clip port on the switch for a hard reset. I did unplug it, but don’t see any other method on this unit.
 

tgl

Regular Contributor
I'd venture that the switch is not the source of your problems. Plain unmanaged ethernet switches like the GS108 have basically no user-visible state --- they know which MAC addresses are hanging off which of their ports, but the protocols for automatically updating that info when you change cabling arrangements are ancient and very reliable. I could believe an outright-faulty switch, but not if you tried two different ones with the same results. The switch is *certainly* not in charge of giving you an IP address; it only knows about MAC addresses, which are a lower protocol layer.

Likewise, I don't think the cable modem is the problem. It doesn't, or shouldn't, know what's behind the router.

Faulty Ethernet cables are a thing too, but you said you already tried swapping cables.

That leaves the Eero router. Have you updated its firmware or configuration lately?

People on these forums often recommend factory-resetting routers and setting their configuration up from scratch. That always strikes me as having more than a whiff of waving a dead chicken; but in the absence of any other ideas, it seems worth trying here.

Also, if you have any friends you can borrow a router from, swapping something else in for the Eero would be informative. I wouldn't recommend springing for a new router just yet, but that might be the end game here.
 

Tech Junky

Very Senior Member
Ok, so you have comcast. Are you leasing the modem or using your own?

If you're using Eero for everything then plugging into or using WIFI from that device should work and if it is then the switch should work as well.

If the Eero isn't working or you're using WIFI from the CM instead of Eero then there may be a conflict based on the MAC of the devices connecting to the CM. Some CM's operate as a router / wifi and others are basically just a bridge that pass along the public IP to the router attached to them.

If you login to the Eero and look for the WAN IP it should be anything but 192.168.x.x / 172.x.x.x / 10.x.x.x. If it's not then the modem is not bridged and could be a source of issues depending on the use of the network attached to it.

As to the static IP situation. Don't use the W10/W11 easy option. Open control panel / network / change adapter settings / right click on the LAN and hit properties and edit the IP info directly. The "easy" windows option is a pile of junk when trying to assess a network issue and doesn't allow for in depth configuration changes to troubleshoot issues.

1652587009258.png


Right now it could be a handful of things but, it's suspicious that 3 switches aren't working and had been working before this started which narrows things down to the CM or Eero. More info though helps assess which it is that's causing the issue. If the CM isn't bridged it's one thing and if the Eero is being finicky that's another.

CM<>Eero<>Switch<>PC

CM <> WIFI <> PC = bad
CM <> Eero <> WIFI <> PC = good

How is your wife connected currently?

Are other devices connected and working and if so how are they connected / what are they connected to?

As stated though a dumb switch typically doesn't cause issues and the fact that 3 of them have been an issue points to what they're connecting to (EERO) rather than the switches themselves. But, to test use the 2 device / static option to make sure.
 

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tgl

Regular Contributor
If the Eero isn't working or you're using WIFI from the CM instead of Eero then there may be a conflict based on the MAC of the devices connecting to the CM. Some CM's operate as a router / wifi and others are basically just a bridge that pass along the public IP to the router attached to them.
Given that the OP has accurately identified his cable modem as a Linksys CM3024, there's no WiFi in it, nor any routing/firewall capabilities AFAICS:

user manual for CM30xx

So I think it's basically just bridging from the ISP to the Eero router. That router *should* be creating a local network with NAT mapping to the single IP address that the ISP is providing. It sounds like something is wrong in that area, but hard to be sure what.

I second the question about what the wife was doing that worked for her zoom call -- what equipment was that on, and plugged in how? Also, what "DNS error" are you getting exactly?
 

Tech Junky

Very Senior Member
@tgl

good point that it was mentioned. Also, the DNS error is probably just Comcast having a fit over something and not providing the lookup as expected which leads to using 8.8.8.8 / 1.1.1.1 or some other combination instead of relying on Comcast DNS which sucks and flakes out all of the time.
 

follower

Very Senior Member
I have a Linksys CM3024 cable modem with XFinity internet. That goes into an Eero wireless router. Then out of the router into an 8 port switch to run all the wired components (my PCs, network printer, PlayStation 3 & 4, etc.)

This has worked for over a decade with a basic unmanaged D Link switch. One day it didn’t work anymore. I figured that the switch had more than lived it’s life so I bought a cheap TP-Link TL-SG1008D for like $25 and replaced the D Link. Everything was fine for 3 months and then last night it stopped working again.

I reset everything and tried a different ethernet cable, but it just wouldn’t work. I was annoyed that it only lasted 3 months but figured that the cheap switch just died too.

I bought a Netgear GS108 today and hooked everything up, but it still doesn’t work. So maybe the switch never was the issue? The port lights are coming on and blinking, but none of the devices are connecting.

Wireless works, and if I plug my computer ethernet cord directly into the Eero, it works too. So I’m getting service from the Eero port. But when I run it into the switch, it doesn't seem to be going anywhere after that. PCs, PlayStations, printer, nothing is connected to the Internet.

I am at a loss for what to even look at. Any advice would be appreciated. I thought that it must be a hardware problem with the switch if every component hooked into it stops working at once, but hooking up a new one and getting the same results seems to contradict that.
Contact your ISP.
 

thiggins

Mr. Easy
Staff member
If the port lights are all blinking fast and constantly you have a loop (two connections to the same device). That could certainly cause the problems you describe.

Disable Wi-Fi on the Linksys cable modem to ensure that all devices are on the same subnet.
 

dlister70

New Around Here
That leaves the Eero router. Have you updated its firmware or configuration lately?

I checked and there was a software update for the Eero. I installed this morning. I power cycled the cable modem, the Eero, and the switch. Still no luck.
 

dlister70

New Around Here
If the port lights are all blinking fast and constantly you have a loop (two connections to the same device). That could certainly cause the problems you describe.

You appear to be on the right path! One of my old PCs had constant lights blinking fast on the switch port where it was plugged in.

When I unplug that LAN cable, the rest of the network works again! I'm currently typing from my other PC while connected through the switch, so it's working again. I tested the Playstations and they are back up as well.

I don't even have a monitor or keyboard on the problem PC, as I just remote in when I want to do something with it. Since I can't remote in while it's unplugged from the switch, I'll have to hook up some components and look at the PC later to figure out what the issue is.

There is only one LAN cable in the back of that computer, and only one plugged into the switch so I'm not sure how it could have two connections to that computer, but unplugging it from the network did work, so it's the hottest lead that I've had so far!

Does anyone have any suggestions as to what could be causing the problem computer to do this? It's an old PC that I don't need, and wouldn't mind just removing, so that's certainly an option. When I bought my new PC, I just left the old one hooked up on the network in case I needed to transfer over some file or look up some setting for a program as I was setting up the new PC. But I haven't remoted in for awhile, so there could be some kind of hostile takeover happening on that computer for all I know. :)

Thank you all for your assistance, I'm extremely relieved to have the network up and running again!
 

dlister70

New Around Here
I second the question about what the wife was doing that worked for her zoom call -- what equipment was that on, and plugged in how? Also, what "DNS error" are you getting exactly?

She was on wifi, which was still working the whole time. Everything on wifi still worked (20+ devices), but the only way that I could get ethernet to work was directly out of the back of the Eero, bypassing the switch. Now that I've unplugged the troubled computer that was blinking constantly on the switch, every other ethernet connected device started working.
 

Tech Junky

Very Senior Member
There is only one LAN cable in the back of that computer,
Try plugging it directly into the Eero and see if it works properly. If not then try a different cable and if that fails
replacing the NIC or using a USB NIC as it's probably at fault if it's triggering a loop.
 

tgl

Regular Contributor
You appear to be on the right path! One of my old PCs had constant lights blinking fast on the switch port where it was plugged in.

When I unplug that LAN cable, the rest of the network works again!

Hah, nice debugging work!

Does anyone have any suggestions as to what could be causing the problem computer to do this?

Before you do anything else, try a different ethernet cable to that computer, and then also plug it into a different switch port, just to rule out bad cable or flaky port.

If it's not that, then the PC's NIC is either misconfigured or broken. If you haven't touched its configuration lately then I'd lean towards "broken". Maybe unplugging and replugging things caused a surge that was enough to fry it? Anyway, ethernet PC expansion cards are dirt cheap, so getting another one probably makes more sense than spending a lot of time debugging it.
 

thiggins

Mr. Easy
Staff member
You appear to be on the right path! One of my old PCs had constant lights blinking fast on the switch port where it was plugged in.

When I unplug that LAN cable, the rest of the network works again! I'm currently typing from my other PC while connected through the switch, so it's working again. I tested the Playstations and they are back up as well
Glad the suggestion helped. What is the problem PC used for?
I'd connect a monitor and keyboard to it and run a full virus scan before putting it back on the network.
 

follower

Very Senior Member
If the port lights are all blinking fast and constantly you have a loop (two connections to the same device). That could certainly cause the problems you describe.

Disable Wi-Fi on the Linksys cable modem to ensure that all devices are on the same subnet.
I saw some similar cases a long time ago. But it was not a loop. A broken NIC was sending infinite packets to the entire network 24hours and 7 days a week. The whole network was downed. The solution was simply changing the NIC. It was like a DDOS. The light was constantly blinking like a loop.
Another case was Google Nest Hub and AC88U. Google Nest Hubs sent tons of packets to the entire network at the same time. It was only happened with AC88U which was worst nightmare router. I gave AC88U to my friend. I've talked about it in snbforums years ago.
 
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