[c-nsp] RPS 675 question

[Justin Shore]

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.

Justin