[c-nsp] power requirement for WS-X614E-GE-45AT in reverse POE mode

[Nick Hilliard]

On 01/04/2015 08:38, Gert Doering wrote:
> If I run a WS-X6148E-GE-45AT in reverse POE mode (feeding power into
> the 6500), but do not use the ports for actual switching, will the line
> card still require power?

I've run this configuration in production on a number of occasions and it
works quite well up to and including powering up a fully loaded 6509.

There are two things you need to be careful about: first, you need to
ensure that you get the POE load balancing right across all the port groups
on this particular blade.  If you inject too much power into a single port
group, parts of the blade will suffer from brownout.

>From the supply side, the number of POE injectors needs to be a power of
two, e.g. 1, 2, 4, 8, 16, etc because the power injection load hashing
algorithm is based on the same mechanism as the etherchannel hashing
function so unless you use a power of two, you'll end up with uneven load
distribution and this can cause problems.  I normally use 2^n+1 injectors
and there's a hidden command somewhere which allows you to specify the
minimum number of POE injectors in an injection group.

One of the local data centres is looking into this as a mechanism for doing
remote power supply for some section of their data centres which have
inadequate input power supply.  I'm interested to see how it will scale, as
obviously there are going to be some issues with UTP cross-connects.  I
believe they're also looking at using PoE over fibre, due to the higher
capacity available.  Will let you know how it pans out.

Nick