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Does anyone know if I can purchase a second power supply that goes in a Cisco 3825 router, or is there a separate unit I get for this?

Right now it just the single power supply, and I want to get what I need to have it read for standard A/B power setup at a datacenter.

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3 Answers

up vote 3 down vote accepted

Yep, you need a Cisco RPS2300, which is an external 21U number that can provide PSU resilience for up to 6 other switches or routers concurrently. They're about $1k each.

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Says it is 1U ? –  Kyle Brandt Jan 28 '10 at 17:03
    
what's a U between friends ;) - actually they're very unbalanced weightwise so a little harder to handle than most 1U boxes, hence my error. –  Chopper3 Jan 28 '10 at 17:09
    
So this site, cisco.com/en/US/prod/collateral/routers/ps5855/…, says RPS 675 "Yes. RPS is supported externally on the Cisco 3825 by connecting to Cisco RPS 675. The RPS connector to the external RPS unit is built into the platform and can operate with or without the presence of a system power supply." But anyways, so would I have one of these connected to the PS in the router and the other the RPS device, for example with the RPS device going to A and then the builtin PS going to B power? –  Kyle Brandt Jan 28 '10 at 17:13
    
The 675 has been discontinued AFAIK, plus we had loads and they were sh1t :) –  Chopper3 Jan 28 '10 at 17:16
    
Sorry, to answer the second part of your question yes, that's exactly what you do, they have a cable (quite an odd one) that goes to that white port on the back - you generally have to reload the switch/router for it to recognise the RPS though which is a pain. –  Chopper3 Jan 28 '10 at 17:18
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I'm not aware of a secondary PSU for the 3825, but you can take advantage of A/B power by using a Transfer Switch.

http://www.apc.com/products/family/index.cfm?id=14

I've just moved you from one SPOF (the router PSU) to two SPOFs (the PSU and the transfer switch), but now atleast you can lose A or B power and you won't lose your router.

I've used this solution on devices that I only found out too late didn't have dual power supplies.

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You still have a SPOF w/ the router PSU. What happens when the cable gets knocked out? Or the PSU decides it doesn't feel like working anymore? –  Zypher Jan 28 '10 at 17:19
    
That's what I said too... You add another SPOF, but you get A/B power redundancy. Unfortunately I've had more power blips than PSU failures on Cisco gear. –  Joel K Jan 28 '10 at 18:57
    
Reading comprehension fail. sorry bout that. And yes, I've had the same experience w/ power blips vs cisco PSU failures. –  Zypher Jan 28 '10 at 23:14
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Oops - brain not fully engaged. 3825 is single PSU. 3845 is dual. Pretend I never said that :-)

The 3825 can handle redundant power supplies & they're available for purchase from most Cisco resellers -- Hit up Google Shopping or similar to go price hunting though, there's a pretty wide range of prices for new vs. refurbs.

The part number is PWR-3825-AC (or -DC if you use DC power)

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How sure of this are you? I see "External Cisco RPS 675 (3825) or internal (3845)" on cisco.com/en/US/prod/collateral/routers/ps5855/… . –  Kyle Brandt Jan 28 '10 at 17:08
    
Yup - Just realized I was looking at the wrong section of the 38xx book. Chopper3 has the right idea: The RPS will cover you from anything except a PSU failure in the 3825. –  voretaq7 Jan 28 '10 at 17:12
    
voreteq7: So if the power supply in the router fails, the RPS system doesn't help? –  Kyle Brandt Jan 28 '10 at 19:00
    
"• Internal power supply failures in network devices • Failure of an AC circuit (a circuit breaker tripping, for example) • Interruption of utility power The Cisco RPS 2300 can address the first two issues. " -- They lie? –  Kyle Brandt Jan 28 '10 at 19:01
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