WRTMerlin & Small Business Switch = Dead Network

[Percius]

Hello & Please Help,

I am experiencing something I cannot explain nor do I have a good idea how to troubleshoot. Short version: When a "BAD"device is connected to a switch, the connection between the switch and router drops. I cannot figure out a way to determine (excluding trial and error) which device is the bad device or what is actually happening to cause the network to go down.

I have 2 networks with Asus RT-AC6800U Routers running Asuswrt Merlin. 1 is connected to a Netgear S3300-X28 switch. The other is connected to a Cisco SG200-26 port switch.

In both cases when a "BAD" device is connected to the switch I loose connectivity between the switch and router. In 1 case this is a particular FOSCAM camera (Not definitive if cable maters yet). Note 3 identical cameras including firmware do not cause this issue (Yet). In the Other case it was a Desktop with a Intel NIC running Intel AMT. For the desktop once it was powered down for 24hrs the issue cleared and has not reproduced though a year ago a laptop with intel AMT caused the same issue.

I am looking for ideas on how to tell what the issue is, whats causing it without turning off 1 port at a time, and how to prevent it.

P.S. I have a reasonable familiarity with Networking, Bash consoles, Ip Tables, etc but am not a expert in this field.

Thanks.

 

[sfx2000]

First guess - bad cable - both the netgear and cisco switches should be able to indicate that on the port status...

 

[Percius]

First guess - bad cable - both the netgear and cisco switches should be able to indicate that on the port status...

I have thought about this. Both switches report the cables good (to "bad" device as well as to switch). Even still in both cases the system runs for days without the offending device connected. In the cisco case the network failed in approx 2min after offending device was plugged in. In Netgear case it was 2-3min. (Note after a power cycle long enough to reset intel's AMT system that no longer replicates the issue.)


If it was a cable issue, what kind of cable issue would take down the switch to router? Assuming cable is not the cable between the switch to router (which i presume since that cable handles load just fine if non-offending device is not plugged in).

 

[sfx2000]

Could be a cross-over or straight through cable - the Cisco switch should have an option for Auto-MDIX, see if that's enabled or not.. same goes with the netgear.