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Rising star

C9k: Why use more than 350W PSU if not a POE switch?

Hi everyone,

 

Some switches which don't use POE have large PSUs by default. Such as the new 9300-24S which is 24 SFP's and no POE support,but defaults to 715W PSU.

 

https://www.cisco.com/c/en/us/products/collateral/switches/catalyst-9300-series-switches/nb-06-cat9300-ser-data-sheet-cte-en.html 

 

Why would it default to that, and why bother with more than 350W (it's supported)?

 

Why would 

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VIP Mentor

Re: C9k: Why use more than 350W PSU if not a POE switch?

i cant answer on specific devices you would need to check that with Cisco , but generally same as pcs and other devices which use psus thats why having a higher PSU is better than lower PSU

"It seems as though the 9300-24S specifically requires it even though no POE is involved."

There could be a certain design requirement for that 9300-24s switch they are not all identical in hardware, it looks like all S series require 715 looking at the sheet so i would think its something to do with internal in the switch

If you want to get into the technical aspect of it , read the below link goes into lot of factors involved why having a larger PSU is better

https://www.corsair.com/ww/en/blog/why-does-a-better-power-supply-mean-a-better-computer-experience/

Your main concern is if you are using POE whether you have enough power to draw from based on the devices you are connecting to the switch and what type of POE they use

the price difference is minimal but i would go with what there suggesting unless you require more POE , i wouldnt add anything less than the spec sheet states

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VIP Mentor

Re: C9k: Why use more than 350W PSU if not a POE switch?

Hi

a better power supply can make the device last longer , helps with cpu cycles and keeps the motherboard operating longer , youll get away with 350 butthere advising to use a 715 for longevity and better performance

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Rising star

Re: C9k: Why use more than 350W PSU if not a POE switch?

But why would they suggest a 9300-48T use 350W when it has twice as many ports as 9300-24S, assuming it's "best practice" to always use a larger PSU? It seems as though the 9300-24S specifically requires it even though no POE is involved.

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VIP Mentor

Re: C9k: Why use more than 350W PSU if not a POE switch?

i cant answer on specific devices you would need to check that with Cisco , but generally same as pcs and other devices which use psus thats why having a higher PSU is better than lower PSU

"It seems as though the 9300-24S specifically requires it even though no POE is involved."

There could be a certain design requirement for that 9300-24s switch they are not all identical in hardware, it looks like all S series require 715 looking at the sheet so i would think its something to do with internal in the switch

If you want to get into the technical aspect of it , read the below link goes into lot of factors involved why having a larger PSU is better

https://www.corsair.com/ww/en/blog/why-does-a-better-power-supply-mean-a-better-computer-experience/

Your main concern is if you are using POE whether you have enough power to draw from based on the devices you are connecting to the switch and what type of POE they use

the price difference is minimal but i would go with what there suggesting unless you require more POE , i wouldnt add anything less than the spec sheet states

View solution in original post

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Rising star

Re: C9k: Why use more than 350W PSU if not a POE switch?

I'll punt it up to the RP (our account manager).

 

Thanks :)

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Hall of Fame Community Legend

Re: C9k: Why use more than 350W PSU if not a POE switch?

It is a 24S (24 ports SFP). This is not a PoE but it is "close enough": The power required to power up all the SFP requires more than what 315w can provide.
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