One C9606R rebooted with loss of 2 PSUs but the other did not.

[stonent01]

We have a dual 9606R stack linked together with VSS.   We had a street power blip today and it caused switch 2 in the stack to reboot.  Switch 1 did not reboot.  The loss of power was approximately 10 seconds. I think.

The front power supplies on both switches are as follows.

UPS-A   Street  Street  UPS-B

We traced out the cables and confirmed they were correctly connected as documented to 120V 20AMP lines and to the correct oulets.

We had assumed maybe incorrectly that we can suffer the loss of 2 PSUs and the core should continue running, correct?  But then why would switch 1 continue working when switch 2 did not?

Here is the HW inventory of the core.

NAME: "Switch 1 Chassis", DESCR: "Cisco Catalyst 9600 Series 6 Slot Chassis"
NAME: "Switch 1 Slot 1 Linecard", DESCR: "48-Port 10GE / 25GE"
NAME: "Switch 1 Slot 2 Linecard", DESCR: "48-Port 10GE / 25GE"
NAME: "Switch 1 Slot 3 Supervisor", DESCR: "Supervisor 1 Module"
NAME: "Switch 1 Power Supply Module 1", DESCR: "Cisco Catalyst 9600 Series 2000W AC Power Supply"
NAME: "Switch 1 Power Supply Module 2", DESCR: "Cisco Catalyst 9600 Series 2000W AC Power Supply"
NAME: "Switch 1 Power Supply Module 3", DESCR: "Cisco Catalyst 9600 Series 2000W AC Power Supply"
NAME: "Switch 1 Power Supply Module 4", DESCR: "Cisco Catalyst 9600 Series 2000W AC Power Supply"
NAME: "Switch 1 Fan Tray", DESCR: "Cisco Catalyst 9600 Series C9606 Chassis Fan Tray"

NAME: "Switch 2 Chassis", DESCR: "Cisco Catalyst 9600 Series 6 Slot Chassis"
NAME: "Switch 2 Slot 1 Linecard", DESCR: "48-Port 10GE / 25GE"
NAME: "Switch 2 Slot 2 Linecard", DESCR: "48-Port 10GE / 25GE"
NAME: "Switch 2 Slot 3 Supervisor", DESCR: "Supervisor 1 Module"
NAME: "Switch 2 Power Supply Module 1", DESCR: "Cisco Catalyst 9600 Series 2000W AC Power Supply"
NAME: "Switch 2 Power Supply Module 2", DESCR: "Cisco Catalyst 9600 Series 2000W AC Power Supply"
NAME: "Switch 2 Power Supply Module 3", DESCR: "Cisco Catalyst 9600 Series 2000W AC Power Supply"
NAME: "Switch 2 Power Supply Module 4", DESCR: "Cisco Catalyst 9600 Series 2000W AC Power Supply"
NAME: "Switch 2 Fan Tray", DESCR: "Cisco Catalyst 9600 Series C9606 Chassis Fan Tray"

[Leo Laohoo]

What if it was due to a crash? 

Please share the output to the following commands: 

sh log on switch standby uptime detail
sh log on switch standby messages detail

[stonent01 · Accepted solution]

Unfortunately the logs rolled over and I don't have the logs but I do think I have figured it out. 

The idle power usage from show power is 2460 watts. I noticed the PSUs said they had a capability of 1050 watts which meant losing two would drop below the amount required to function. I pulled up the technical docs on the switch and it says to get the full 2000W capability you must run at 240V. 

Our old 6880 core required 240V but the cables were different so we just used the 120V cables that came with the 9606. 

I've come up with a way using an auto transfer PDU to keep at least 3 PSUs online in the event of a street power loss again until I can get some twistlock cables with a c15 end on them in order to tap into our 240V circuit. 

[stonent01]

Apparently another division of my company had already dealt with this but didn't share the information with my site.  Maybe Cisco should update the documentation on the 9606 to indicate they strongly suggest against running on 120V if there is possibility of losing more than 1 power supply at a time.

I have found a single 208 feed that's unused that I can tap into to get at least 1 leg of the power on a higher capacity.