power supply for 6500

Unanswered Question
Jun 23rd, 2008

Dear All,

When I use power calculator (www.cisco.com/go/powercalculator) to calculate the power supply needed for a 6500 (e.g. 6509E) switch. If I use a sup7203B with 4 x WS-X6748-GE-TX (with DFC3a), 1 x WS-X6704-10GE (with DFC3B) and 3 x WS-X6748-SFP (with DFC3A). The result display that the total power is 3323.88w and need a 4000w primary power supply. But the strange thing is, the result also display:

First Alternative Power Supply

Combined WS-CAC-2500W

So that means I can use a 2500w power supply as secondary power supply? or means that I need to use 2 x 2500w power supply? if I use 2500w power supply, what happen if 1 x 2500w power supply fails?

Thank you!

Best Regards,

Teru Lei

I have this problem too.
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Collin Clark Mon, 06/23/2008 - 07:25

You would need 2x2500 PS. If one were to fail, line cards would start to shut down and possibly the SUP! If you buy 2x4000 PS you can lose a PS and the switch will stay up and running.

Hope that helps

cyphur353 Mon, 06/23/2008 - 07:27

Collin nailed it - you can either run the PSU's in combined or redundant mode. Combined mode allows lesser PSU's to be used however as Collin noted, if you lose a PSU, you start dropping line cards as you now cannot meet the power capacity requirements of your box.

Best bet - 2x 4000w, if the budget allows.

teru-lei Mon, 06/23/2008 - 07:59

Thanks for the reply. But I wonder if in 2 x 2500w, one power supply fails and some line card drop, and that may cause performance issue. e.g. HSRP, routing and spanning-tree. Seems it's better to shutdown the whole switch in this case. Is there any document to describe this scenario??


Collin Clark Mon, 06/23/2008 - 08:04

Then you should buy one 4500w (and maybe another one as a shelf spare).


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