PSA: Avoid CBS350 Switches - Critical POE Defect

[d0nni3q84]

Hello Community,

I'm writing to let you know that there is a critical POE defect in the CBS350 switches and you should avoid them if you require stable POE operations. This apparent software defect causes POE ports to randomly fault after 8 to 12 hours and the powered device will go offline. Cisco does not have a resolution, workaround, or timeline to address this situation.

Please help Cisco prioritize this issue by opening a TAC case if you are experiencing this issue. Additionally, please escalate this for additional visibility through your sales channels.

All the best!

[jimstewart77]

Can't say that I have seen this on CBS350-10Ps, which switch model/s are you experiencing this on and which devices are falling over?

[d0nni3q84]

I'm observing this on CBS350-24P-4G and CBS350-8P-E-2G running 3.1.1.7 firmware. What version of firmware are you running?

[cyberconsultants]

What PDs are faulting?

[d0nni3q84]

This issue happens on ports that do not have any powered devices connected. For the ports that do have powered devices, they are:

• Ubiquiti Access Point AC Long-Range (UAP-AC-LR)
• Ubiquiti Camera G3 Bullet (UVC-G3-BULLET)

[cyberconsultants]

And what happens when they fault?

[d0nni3q84]

This issue happens on ports that do not have any powered devices connected as well. When the CBS350 switch faults the port, it no longer supplies power to the port and the powered device turns off.

[cyberconsultants]

Hm.

[jimstewart77]

Also 3.1.1.7 on a CBS350-8P-2G. 

Have yet to see a PoE issue myself and have been running a fair few PoE (not +) devices. Concerning to hear of the issues.

[d0nni3q84]

Thanks, @jimstewart77 ! Could you share the output of show power inline from your CBS350-8P-2G?

[jimstewart77]

kauwbergSW#show power inline

Power-limit mode: Class based
Usage threshold: 95%
Trap: Disable
Legacy Mode: Enable
Inrush Test: Enable
Guard-Band Value: Static (2W)

Unit Module Nominal Consumed Temp SW PSE chipset
Power (W) Power (W) (C) Version HW Revision
---- -------------- --------- ------------ -------- ------------- -----------------
1 CBS350-8P-2G 60 10 (17%) 38 0.2.0.17 TPS2388 - 0x40C4

Interface Admin Oper Power (W) Class Device Priority
---------- ---------- ----------- ----------------- ----- -------------- --------
gi1 Never Off 0.0 - low
gi2 Auto On 5.673 4 WiFiAP low
gi3 Auto Off 0.0 - DMRhotspot low
gi4 Auto Searching 0.0 - low
gi5 Auto Searching 0.0 - low
gi6 Auto On 3.056 0 low
gi7 Auto On 1.231 1 low
gi8 Auto Searching 0.0 - low

[jimstewart77]

randomly ran into this article on UAP items and issues with Cisco Catalysts, wonder if its related to your issue

https://community.ui.com/questions/Workaround-for-UAP-AC-802-3at-non-compliance-POE-power-problems-reboots-for-newer-Cisco-catalyst-/baf59f23-e89c-4042-8349-d05b6e3e95b7

[d0nni3q84]

Possibly, but what concerns me is that my 8P device right now has nothing plugged in and the POE ports have a mind of their own going into searching and ultimately fault, despite the power inline never command being set.

[cyberconsultants]

I can confirm Searching behavior for PoE ports on an SG350X with power inline never set. This is with limit-mode in either class or port, and with or without a limit explicitly set. This wouldn't have anything to do with any faults, it doesn't mean "PoE operations" are being performed, and it's certainly not a critical defect in either switch family. Per this documentation, "Port is off. Detection is in process" is a valid status. I don't know what the timeout is exactly, but these ports should eventually return to Off/"Port is off. User setting" status.

I'd recommend using class limit mode on your switch so that the classification stage can occur according to 802.3 standard (or as close to standard as possible). Power limit mode is in no way a hardening setting. You should also re-enable inrush test.

Whatever's happening with your PDs is likely better suited as a PSA re: Ubiquiti's PoE implementation.

[d0nni3q84]

Thank you for sharing your assessment; however, my concern is not with ports going into the "Searching" status. The concern and situation is specifically with ports going into the "Fault" status and not delivering any POE. This happens without any powered devices connected as well. Please observe the below output and explain that to me. Also, while I do not disagree with changing those settings, they were advised to be set by TAC for troubleshooting, who by the way finally admitted this is a known software defect with no ETA.

SW-3#show system | i Description
System Description:                       CBS350-8P-E-2G 8-Port Gigabit PoE Managed Switch

SW-3#show power inline
Power-limit mode: Port based
Usage threshold: 95%
Trap: Disable
Legacy Mode: Enable
Inrush Test: Disable
Guard-Band Value: Static (2W)

Unit Module         Nominal   Consumed     Temp     SW            PSE chipset
                    Power (W) Power (W)    (C)      Version       HW Revision
---- -------------- --------- ------------ -------- ------------- -----------------
1    CBS350-8P-E-2G 60        0 (0%)       47       0.2.0.17       TPS2388 - 0x40C4


Interface    Admin       Oper         Power (W)     Class     Device     Priority
---------- ---------- ----------- ----------------- ----- -------------- --------
gi1        Never      Fault       0.0               -                    low
gi2        Never      Fault       0.0               -                    low
gi3        Never      Fault       0.0               -                    low
gi4        Never      Fault       0.0               -                    low
gi5        Never      Fault       0.0               -                    low
gi6        Never      Fault       0.0               -                    low
gi7        Never      Fault       0.0               -                    low
gi8        Never      Fault       0.0               -                    low


SW-3#show power inline GigabitEthernet 1

Interface    Admin       Oper         Power (W)     Class     Device     Priority
---------- ---------- ----------- ----------------- ----- -------------- --------
gi1        Never      Fault       0.0               -                    low


Port Status:               Port is off. Overload state
Port standard:             802.3AT
Admin power limit:         0.0 watts
Time range:
Max Power Allocation:      0.0 watts
Spare pair:                Disabled
Negotiated power:          0.0 watts (None)
Current (mA):              0
Voltage(V):                0.0
Overload Counter:          68
Short Counter:             0
Denied Counter:            0
Absent Counter:            0
Invalid Signature Counter: 0