[c-nsp] RPS 675 question

[Seth Mattinen]

Justin Shore wrote:
> andrew2 at one.net wrote:
>> I'm getting ready to install some RPS 675's in order to dual cord some
>> 3750's and ran across this in the manual:
>>
>> "Do not use different power sources to power up the RPS and the connected
>> device.  If you connect to separate AC power sources, reset conditions
>> might
>> occur."
>>
>> Huh?  My intent is to plug the RPS into a different PDU than the actual
>> switches so that the switches can stay online in the event of a power
>> failure on their primary circuit.  Is this Cisco FUD or are there good
>> reasons I wouldn't want to plug an RPS into a different circuit than the
>> connected switches?
> 
> The only possible problem that I can foresee is the potential to create
> a ground loop.  That wouldn't be good.  The RPSs are only meant to
> protect against a power supply failure, not a power source failure.
> 
> That said, I use a RPS 675 in the same way that you're describing
> without any problems.
> 
> Also, remember that the RPS 675 can only keep 1 connected device powered
> up in the event of a power failure.  The RPS 2300 can do 2.  Ie, if you
> have a stack of 4 switches with 2 connected to circuit A, 2 connected to
> circuit B, the RPS connected to circuit C (with all 4 switches connected
> to that RPS) and circuit B fails, only 1 of the 2 switches connected to
> circuit B will get power from the RPS.  The other will be dead in the
> water.
> 

Don't forget rebooting to go back to internal power. Except on 2088
series routers with an AC-IP power supply; they can switch back fine.

~Seth