Power supply question in 6500

Unanswered Question
Sep 23rd, 2007
User Badges:

I had a power supply failure in 6506, I replaced it with the spare but when I inserted it i found out that it was a 3000W power supply and my original was 2500

PS1-Type PS2-Type

-------------------- --------------------

WS-CAC-2500W WS-CAC-3000W

and now look at this log

2007 Sep 23 04:22:59 %SYS-1-SYS_DISABLEPS: Rating of power supplies in redundancy not equal, power supply 1 disabled

My questions is:

Now that PS2 is active and I need to replace PS2 when I get an RMA from Cisco, will this replacement reboot my switch, or if it will failover transparently. I'm scared to do anything until I'm sure what it will do.


  • 1
  • 2
  • 3
  • 4
  • 5
Overall Rating: 3 (2 ratings)
JORGE RODRIGUEZ Sun, 09/23/2007 - 07:48
User Badges:
  • Green, 3000 points or more

Nawaz, power redundancy is by default enable. When two power supplies of equal watts are used the two PS watts are combined to service the switch and modules, if one fails the switch will function normarly but will accomodate power proportional to its capacity for providing enought power for modules, if you have fully populated switch for example with PoE blades some may be disable because of luck of power but the switch will continue working, but I guess this is not your case.

In your case you have power redundancy enable by default, in this unequal power scenario the switch will use the highest capacity PS and disable the lower capacity,

this happaned when you installed the 3000, and the power transition switched transparently. Once you replace PS1 2500 with a 3000w your switch does not and will not reboot and redundant power will auto configure transparently.

As a rule of thumb treat every change in hardware or software as an anounced maintanance to be done after hours.

Go over this link Enabling or Disabling Power Redundancy section, and undertanding un-equal power explaining your scenario.




nawas Mon, 09/24/2007 - 04:51
User Badges:


I don't think you understood my question correctly, I already know how the power gets distributed among the blade and chassis. My scenario is that I have one active and one disabled power supply, I need to replace ACTIVE power supply. I'm sure chassis will think form a moment when it fails over to disabled power supply, this is what I'm trying to find out if it will reboot or if it will transparently failover.


Danilo Dy Mon, 09/24/2007 - 05:06
User Badges:
  • Blue, 1500 points or more


Only Cisco TAC can provide a correct answer.

However, I give you some analysis regarding prower distribution. In your scenario, no power currently distributed from the disabled PS to the chassis, only the active PS is distibuting power to the chassis. The step of replacing PS module is to switch it off, therefore when you switch off the active PS, the chassis will immediately lost power. To make a transparent failover, both PS module should be active before the replacement (the switch off of one of them), and the remaining PS module should be able to take the load to power all modules installed in the chassis.



JORGE RODRIGUEZ Mon, 09/24/2007 - 11:08
User Badges:
  • Green, 3000 points or more

Nawaz, apparently I missunderstood and please take my appologies, however, I provided you with a link that gives the answer to your question , please read it.

If the switch have unequal power supply and one is disable it is because the switch is configured for redundant power which is the default settings.. you can change the settings from reduntant and non-redundant configurations at any time for the 2500W to come online along with the 3000w all as combined power, read table 14-4 1st paragraph " Effects of Power Supply Configuration chnages " in other words you can have unequal power supplies fully operational in a non-redundant configuration. When this is done and replace the 3000w with the 2500w you can put it back to redundant mode.. all this is done with no downtime.




This Discussion