Dual PSU in 4507+E: basic operation in redundant mode

[johnoliphant1]

I'm looking for a little bit of explanation about dual PSUs in Cisco switches.

We have a 4507+E switch, with two 4200W PSUs. I've been digging through the specs, and I think I know how much power the electrical contractor needs to provide, but I want to understand its operation in redundant mode.

Does one PSU carry the load, while the other sits, essentially idle? Then if the first one lets its smoke escape (fails), the second one takes the entire load.

More specifically, the max power for the entire switch is roughly 4200W, even though I have two 4200W PSUs.

-John

[acampbell · Accepted solution]

John,

You have  2 choices
1) Th DEFAULT - Redundant mode - One PSU supplies all power
with the 2nd one in hot standby

2) Combined - Both PSUs share the the load but some cards may loose their poer if
a PSU fails and the remaining PSU can supply any more power

Please see this link
http://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst4500/12-2/31sga/configuration/guide/config/pwr_envr.html#wp1035503

Regards
Alex