CBS250-8PP-D power problem as soon as a computer is connected

[aka_]

Hi there

I want to replace an ubiquity switch whit a device from Cisco. The only switch which meets the form factor requirement is a CBS250-8PP-D.

So I bought one and face a strange problem. As soon as I connect a computer to this switch the switch shuts down like if I remove the power supply. It doesn't matter if the computer is running or not or if the computer even is connected to a power supply. As soon as I remove the patch cable the switch starts again. It doesn't matter on whitch switchport the cable is pluged in.

I changed all cables few times but it did not help. Then I used a USB-Lan adapter and this worked but then I faced the same problem on a different computer which was working before.

I turned off POE on the ports but the problem remains. I disabled green ethernet but the problem remains. I tried different firmwares but the problem remains.

So I made a RMA with the vendor and received a new switch. I took it out of the box and connected it to the computer but the problem remains even whit a brand new out of the box switch whitout any config.

The current ubiquity switch works, a netgear switch works, a unmanaged 5 port zyxel switch works, a catalyst 9200 works.

Does anybody have an explanation or a solution for this? Because the use uf USB-Lan adapter is not really a solution form me especially because all the cheaper switches and the much more expensive one works whit no problem.

Greetings Alex

[Kasun Bandara]

have you tried disabling smart port feature?

[aka_]

It was already disabled. I turned it on and off again but unfortunately the problem is still the same

Alex

[Flavio Miranda]

Hi

 Sounds like some hardware problem and you were luck enough to get 2 with the same problem.  I can not see any other explanation for that. 

 I would try another RMA.

[aka_]

Hi

I did another RMA and the problem is still the same... I guess I have to give up and use those USB-Lan adapter

[aka_ · Accepted solution]

I got a hint that Asus mainboards cloud cause this issue. So I checked all the mainboards of the affected computers and all of them have an Asus mainboard installed. I took the switch to a friend whit no Asus mainboards and all of his computers worked whit no problem.

It's still strange that the CBS is the only switch which has the problem whit the power but the failure source are the Asus mainboards. So I use USB-Lan adapters and everthing works now.

[JKIT]

this is not a solution, that's a workaround and the problem is not the Asus-mainboard! I have the same issue if I try to connect this switch to another Cisco CBS350 switch with shielded cable. It just turns off instantly and it will not turn on again if I disconnect the power cable and connect it again! IMHO this is a hardware issue, because the firmware cannot even start to boot.

I have contacted the TAC, but will return the switches, because this wont be solved quickly I guess.

Cisco Small Business switches are really bad quality. I have issues with CBS350 switches as well with other not solved bugs.

That was really bad idea to purchase those switches.

[vhud-tv]

Same issue as here:

https://community.cisco.com/t5/switching/cbs250-8pp-d-is-crashing/td-p/4675099

This is a design flaw which exists for min. 10 years now. It is related to shiedling. While the 19" switches are not impacted, the smaller ones are crap.

[MichaelDavid]

It sounds like there could be a compatibility or grounding issue between the CBS250-8PP-D and your devices. Since other switches work fine, you may want to check the electrical setup or try a different power supply to rule out any power-related issues.

[vhud-tv]

No, it is not. I experienced this with different kinds of Cisco 8 port gigabit switches in different installations, from small offices to large ones. Older Fast Ethernet switches did also not show this behaviour. I now ordered Catalyst 1200 and am curious about the outcome.

[JKIT]

I can tell you the outcome. It works without issues, as I have tested it already.

I took the burden on me and have tried to solve this issue with Cisco together. We have tested different CBS250-8PP-D switches, exchanged the power supplies, different cables, etc. Nothing helped! Finally they sent me Catalyst 1200 to make a test and it works without any problems! I have opened the case on 20.12.2023 and I'm still waiting for final decision from Cisco. 

[vhud-tv]

Well, we resell those devices - guess it is worth a try to have them replaced with Catalysts by Cisco Thank you for your response.