Connected Switches Keep Disconnecting

[bryan_moore]

I am having an issue with devices connected to my Asus RT-AX86U (running Asuswrt-Merlin firmware 3004.388.9_2) through a hardwired unmanaged network switch randomly disconnecting and needing me to power-cycle the switch to bring them back. I have two different switches that I've used to determine if it is a bad switch or an issue with the router/firmware—one is a TP-Link 8-port gigabit desktop switch (TL-SG108) and the other a TRENDnet 8-pot gigabit GREENnet switch (TEG-S82G)—and I have the same issue with both switches, which makes me think the issue isn't with them.

The logs don't seem to be any help, so I'm not sure really where to troubleshoot next; any help would be greatly appreciated...

 

[bennor]

What troubleshooting steps, other than trying a different switch(s), have you tried? Have you tried a different Ethernet cable? Have you tried different network port(s) on both the router and switch? Have you changed any of the LAN settings on the router? Are you running any addon scripts? Have you checked the power supply to both the router and network switches? Are any other electronic devices in the location being used or exhibiting an issue around the same time the network switch disconnects. Are there any other local network actions or devices being used/powered on around the same time the network switch disconnects?

 

[bryan_moore]

Thanks for the ideas...

I've already tried different ports, which didn't solve the issue; I've never changed any LAN settings nor are there any addon scripts being used. The power supplies are all good as per my multimeter and there are no other electronic devices with any issues. Similarly, there are no network events occurring when the disconnects happen.

The only suggestion I haven't done is replace the cable.

 

[degrub]

Turn off "green ethernet" if you can.

 

[bryan_moore]

That's not an option and wouldn't explain the issue persisting with the "non-green" TP-Link switch...

 

[degrub]

Are you LAGging any of the ports ?

Cable termination issues usually will drop the link rate from 1000 to 100 or less but you may have a noisy cable. What are the link rate lights on the switch uplink port doing during these events ? What about the lights on the port that has a client go offline ?

If the drop offs are random, do they correspond to any electrical device turning ON ?

Do swap out the LAN uplink cable with a know good cable.

 

[bryan_moore]

Sorry, but I have no idea what "LAGging' means...

The lights on each port look to be doing nothing different when things are disconnecting and their doesn't seem to be any devices going on or off when the issue occurs.

 

[degrub]

LAG = Link Aggregation - where one configures two ports to operate together on both ends of the cable to get higher throughput for multiple clients. Does not help for single client access to a device. In the case of this router, the specs indicate this can be done on the WAN side and/or the LAN side of the router.

What do you mean by "disconnecting" ? What exactly are you seeing ?

 

[bryan_moore]

Got it... I've changed absolutely no settings, ever, and the devices connected to the switch will lose network connection, requiring me to power-cycle the switch to get them back. There doesn't appear to be anything odd happening in the router's logs, so at first I thought it had to be a switch that went "bad;" however, the issue persists regardless of which switch I use.

 

[degrub]

It is possible that the switch in the router is going bad. Definitely connect a known good cable from one of the clients seeing the issue to the same router port, completely bypassing the switch. If the issue doesn't change, then probably time to replace the router.

If that fixes it, then replace the cable from the switch to the router with a known good cable.

when you say 'lose network connection" , does that mean lose internet or lose LAN connection ?

 

[bryan_moore]

I suppose I could also simply change which port I'm using on the back of the router, too, come to think of it... Never tried that.

 

[bennor]

I suppose I could also simply change which port I'm using on the back of the router, too, come to think of it... Never tried that.

Which was one of the suggestions above...

Have you tried different network port(s) on both the router and switch?

 

[bryan_moore]

Which was one of the suggestions above...

Went back and re-read that!

It turn out that the port I thought might be giving me issues isn't even the one the switch was plugged into, so I've checked all four ports on the router and all are functioning properly.

I've replaced the cable and will test for a while to see if it pops up again; I'll come back with any additional info...