need help with network loop.

[Spydawg]

Maybe someone can help me..

I have been having an issue with one switch locking up with what I thought was a faulty switch. I'd have to restart the switch to get it to work again.
I picked up a replacement switch a newer Qnap one. It has an led that lights up if it detects a network loop. I have 4 computers hooked up to it and a network cable going to another switch in another room.
One of the computers that is hooked up to it when its on its fine, as soon as I turn off that computer, the switch lights up the led for the Network loop detection.
The other computers on that switch don't do this. Also if I pull the power supply power cord out of that computer the led network led light goes off and as soon as I plug it back in the led light comes back on.

Any ideas?

Those 2 switches are hooked up to my RT-AX88U running latest merlin build.. if that matters

 

[Tech9]

Any ideas?

Check if this PC has "bypass mode" in NIC settings. If it does - disable it.

 

[ColinTaylor]

It sounds like the switch is incorrectly thinking the PC is causing a network loop and therefore going into blocking mode. Given what you said about powering off the PC I'd guess that it's caused by the PC's BIOS standby mode. Look at the BIOS power management options and also any wake on LAN settings.

 

[Spydawg]

thanks will check

 

[sfx2000]

It sounds like the switch is incorrectly thinking the PC is causing a network loop and therefore going into blocking mode. Given what you said about powering off the PC I'd guess that it's caused by the PC's BIOS standby mode. Look at the BIOS power management options and also any wake on LAN settings.

Sounds reasonable...

This is one of the times where STP is useful - it doesn't hurt to enable it - the switch in the router supports it, and most managed switches do as well..

STP is all about loop discovery and resolution...

As to root cause - I'd look at the NIC itself at the suspect computer - this is easy, disable the onboard NIC and use something like a USB ethernet adapter..

I would also consider the cable run - ethernet cable running parallel to a power cable, one can get induced noise triggering loop detection - that's why we always run them apart and cross them at an angle...

 

[heysoundude]

Sounds reasonable...

This is one of the times where STP is useful - it doesn't hurt to enable it - the switch in the router supports it, and most managed switches do as well..

STP is all about loop discovery and resolution...

As to root cause - I'd look at the NIC itself at the suspect computer - this is easy, disable the onboard NIC and use something like a USB ethernet adapter..

I would also consider the cable run - ethernet cable running parallel to a power cable, one can get induced noise triggering loop detection - that's why we always run them apart and cross them at an angle...

STP in this case means Spanning Tree Protocol…but later in the post it can be taken to mean Shielded Twisted Pair cable, which minimizes signal noise. And then there’s SFTP cabling and file transfer protocol…oh my. How do we keep everything straight? And crossing at right angles?

 

[Spydawg]

Thanks guys, turned out to be a bios setting.. not sure what one.. I disabled all power settings I could find for network/lan I could find..

 

[coxhaus]

Spanning tree is your friend when using switches. The bigger your network the faster you need convergent.

 

[DJones]

Spanning tree is your friend when using switches. The bigger your network the faster you need convergent.

Unless you have a server with proxmox then STP is probably going to cause issues.

Least that seems to be the case for me.

 

[coxhaus]

Cisco has many different levels of Spanning tree. Sense my network is small I use a slow version. I don't run switches without Spanning tree protocol.

I don't run proxmox but I use Spanning Tree protocol. As far as I know I don't let servers have control of my network.