combined and redundant mode for power supplies in 4500,6500

Answered Question
Dec 15th, 2008

Hi every body!

I have few questions:

combined mode:

Let me quote from my cisco press book:

" If one power supply fails in combined mode, the switch powers down some of its modules until the required power load can be met by one functioning power supply."

How does switch determine which module's power be turned off first?

Redundant mode:

How can we determine which power supply is suppling power to modules in switch.Is it power supply #1 or #2?

thanks a lot!

I have this problem too.
0 votes
Correct Answer by Edison Ortiz about 7 years 11 months ago

You are indeed correct and I should amend my last sentence, my last sentence is only true in combined mode, not redundant - my apologies - long day :(

According to the link I posted on the 4500:

Redundant mode-Redundant mode uses one power supply as a primary power supply and the second power supply as a back-up. If the primary power supply fails, the second power supply immediately supports the switch without any disruption in the network. Both power supplies must be the same wattage. A single power supply must have enough power to support the switch configuration.

HTH,

__

Edison.

  • 1
  • 2
  • 3
  • 4
  • 5
Overall Rating: 5 (2 ratings)
Loading.
Edison Ortiz Mon, 12/15/2008 - 15:37

How does switch determine which module's power be turned off first?

It goes from the bottom module to the top module, with the exception of the Supervisor module, that's turned off last.

The above behavior is only seen during bootup, not while adding modules in a running switch.

If you have a running switch and try to insert a module which exceeds power requirement, the module won't be turned on and current working modules won't be turned off.

Here is a good link on the 4500 model:

http://www.cisco.com/en/US/docs/switches/lan/catalyst4500/12.2/31sga/configuration/guide/pwr_envr.html#wp1035469

As for the redundant mode, a module isn't drawing from a specific power supply, it's drawing power from both at the same time.

HTH,

__

Edison.

sarahr202 Mon, 12/15/2008 - 16:09

Thanks Edison !

Let me quote from my cisco pres book.

" By default, a switch is configured for redundant mode. If two power supplies are installed and functioning,they are managed as redundant replacements for each other.Both supplies are enabled and active,as if they were both supplying power. In fact, you probably won't be abl to tell which supply is actually powering the switch until one one of them is turned off or fail."

It appears to me, one of the supplies is providing power to switch's modules.

Correct Answer
Edison Ortiz Mon, 12/15/2008 - 16:14

You are indeed correct and I should amend my last sentence, my last sentence is only true in combined mode, not redundant - my apologies - long day :(

According to the link I posted on the 4500:

Redundant mode-Redundant mode uses one power supply as a primary power supply and the second power supply as a back-up. If the primary power supply fails, the second power supply immediately supports the switch without any disruption in the network. Both power supplies must be the same wattage. A single power supply must have enough power to support the switch configuration.

HTH,

__

Edison.

sarahr202 Mon, 12/15/2008 - 16:27

Apology accepted Edison (:)

Thanks a lot Edison!

Now the question is how can we determine which power supply is powering the switch and which one is on back-up?

I saw in book , the power supplies are numbered as 1 and 2. How can we determine which power supply is designated as 1 which power supply is designated as 2?

Jon says though he admits he is not sure.

looking at the back of chassis, the left one is number 1 and right one is number 2.

Any suggestion/correction?

thanks a lot!

sarahr202 Mon, 12/15/2008 - 16:49

Hi Edison!

I find conflicting material about redundant mode. Below is the link.

http://en.wikipedia.org/wiki/Catalyst_6500#6503

I quote from the link:

"Redundant Mode

When running in Redundant Mode, each power supply provides approximately 50% of its capacity to the chassis. In the event of a failure, the unaffected power supply will then provide 100% of its capacity and an alert will be generated. As there was enough to power the chassis ahead of time, there is no interruption to service in this configuration. This is also the default and recommended way to configure power supplies.

[edit] Combined Mode

In combined mode, each power supply provides approximately 83% of its capacity to the chassis. This allows for greater utilisation of the power supplies and potentially increased PoE densities.

In the event of a failure, we power down all devices except the supervisor. During this time, there will be a temporary network outage while we return power to the system. The order at which we do this is as follows:

1. First we power up service modules from the top down

2. Then we power up line cards from the top most slot to the bottom most. We do _not_ permit PoE at this stage.

3. Next we power up PoE from the highest line card and the highest port (i.e. line card 0/port 0) down through to the lowest.

We go through the above until we have hit our power capacity of the remaining power. Normally, a single power supply will be able to power all service modules and line cards, but not give the PoE densities required."

thanks a lot!

Edison Ortiz Tue, 12/16/2008 - 04:56

Hi Sarah,

It's not conflicting material.

My previous post reflected only the 4500. I missed that you were also targeting the 6500 Series, which is a different animal altogether.

The 6500 does draw power from both power supplies:

http://www.cisco.com/en/US/docs/switches/lan/catalyst6500/ios/12.2SX/configuration/guide/pwr_envr.html

To disable or enable redundancy (redundancy is enabled by default) from global configuration mode, enter the power redundancy-mode combined | redundant commands. You can change the configuration of the power supplies to redundant or nonredundant at any time.

To disable redundancy, use the combined keyword. In a nonredundant configuration, the power available to the system is the combined power capability of both power supplies. The system powers up as many modules as the combined capacity allows. However, if one power supply fails and there is not enough power for all of the previously powered-up modules, the system powers down those modules.

To enable redundancy, use the redundant keyword. In a redundant configuration, the total power drawn from both power supplies is not greater than the capability of one power supply. If one supply malfunctions, the other supply can take over the entire system load. When you install and power up two power supplies, each concurrently provides approximately half of the required power to the system. Load sharing and redundancy are enabled automatically; no software configuration is required.

HTH,

__

Edison.

asarlo Tue, 12/16/2008 - 08:51

Hello Edison, my customer has a 6509E with 2 WS-CAC-6000 power supplies. Each power supply have AC input_1 connected to UPS_1 (220V) and AC input_2 to UPS_2 (220V). The total power consumption is 5771.64 Watts. Yesterday they power off UPS_1 and the 8 & 9 module were shutted down because of insufficient power. But both Power Supplies were alive ? what happened ? why don't they use the sum of both supplies wattages (2671.20W x2) ?

I'am attaching the logg.

Thanks a lot ! and regards.

Anacelia

Edison Ortiz Tue, 12/16/2008 - 09:15

In redundant mode, it's not the sum of both but up to 50% of each.

In combined mode, it's the sum of both.

What mode are you running?

__

Edison.

asarlo Tue, 12/16/2008 - 09:19

in redundant mode, but all the power supplies are up!.

Edison Ortiz Tue, 12/16/2008 - 11:47

But the total power consumption is twice the output from the power supplies based on your post. In redundant mode, the total power consumption should be equal to the power output of one power supply.

asarlo Wed, 12/17/2008 - 03:52

Hello Edison, the customer has 2 6000W power supplies configured as redundant. I'am attaching you the "show power" report :

------------------ show power ------------------

system power redundancy mode = redundant

system power total = 5771.64 Watts (137.42 Amps @ 42V)

system power used = 3087.42 Watts (73.51 Amps @ 42V)

system power available = 2684.22 Watts (63.91 Amps @ 42V)

Power-Capacity PS-Fan Output Oper

PS Type Watts A @42V Status Status State

---- ------------------ ------- ------ ------ ------ -----

1 WS-CAC-6000W 5771.64 137.42 OK OK on

2 WS-CAC-6000W 5771.64 137.42 OK OK on

Pwr-Allocated Oper

Fan Type Watts A @42V State

---- ------------------ ------- ------ -----

1 WS-C6509-E-FAN 150.36 3.58 OK

Pwr-Requested Pwr-Allocated Admin Oper

Slot Card-Type Watts A @42V Watts A @42V State State

---- ------------------ ------- ------ ------- ------ ----- -----

1 WS-X6748-GE-TX 363.30 8.65 363.30 8.65 on on

2 WS-X6748-GE-TX 363.30 8.65 363.30 8.65 on on

3 WS-X6748-GE-TX 363.30 8.65 363.30 8.65 on on

4 WS-X6748-GE-TX 363.30 8.65 363.30 8.65 on on

5 VS-S720-10G 338.10 8.05 338.10 8.05 on on

6 VS-S720-10G 338.10 8.05 338.10 8.05 on on

7 WS-X6816-GBIC 269.22 6.41 269.22 6.41 on on

8 WS-X6816-GBIC 269.22 6.41 269.22 6.41 on on

9 WS-X6816-GBIC 269.22 6.41 269.22 6.41 on on

So, if input 1 is off in both power supplies why don't input 2 adjust the output power to supply 5.7K ?

Thanks!

Regards, Anacelia

Edison Ortiz Wed, 12/17/2008 - 07:07

Based on the output, your concerns are correct. I suggest opening a TAC case for further troubleshooting.

__

Edison.

asarlo Wed, 12/17/2008 - 08:06

Edison, thanks a lot for your help.

Regards, Anacelia

Michal Mihaly Tue, 02/14/2012 - 11:28

Hello Asarlo,

we had simillar issues lately. I found out that there 6000W power supplies provide 6000W only if both of the input circuits are at 220V! If either of them drops, it will lower the output to 2900W (that is yours 2671.20W in the log)

http://www.cisco.com/en/US/prod/collateral/switches/ps5718/ps708/product_data_sheet0900aecd801c5c84.html

I open TAC case yesterday to get some recomendation from CISCO, but no answer yet. (Final goal is to have power redundant environment)

If you already know correct answer, please let me know on, thanks.

sarahr202 Tue, 12/16/2008 - 12:40

Excuse my ignorance.

My book did not specify that redundant mode is different for 4500 and 6500 switches. It just says 4500 and 6500 use up to 2 power supplies and they can be used in combined mode and redundant mode.

I had a clear understanding about redundant mode

redundant mode(4500): one power supply is powering the switch while the other is on back up.

Redundant mode(6500): both are

powering the switch , with each powering at 50 percent of its total capacity

I have one question about combined mode.

Is combined mode in 6500 switch same as combined mode in 4500 switch?

My book and links forwarded did

not address this question.

The link says(6500 switch)" In combined mode each supply is powering the switch at 83 percent of its total capacity"

Is it same for 4500 switch or combined mode is different in 4500 switch.

thanks a lot!

Edison Ortiz Tue, 12/16/2008 - 12:53

Sarah,

The link in my first post contains all these information. Here is a section of that link:

When your switch is configured to combined mode, the total available power is not the mathematical sum of the individual power supplies. The power supplies have a predetermined current sharing ratio

HTH,

__

Edison.

sarahr202 Tue, 12/16/2008 - 19:23

Thanks a lot Edison and excuse my oversight.

I did find the all answers to my questions except for one.

How does switch determine which power supply is #1 and which power supply is number #2?

thanks a lot!

sarahr202 Wed, 12/17/2008 - 11:44

Just a quick question.Let me quote from the link.

"If you have the power management mode set to redundant mode and only one power supply installed, your switch will accept the configuration but operates without redundancy."

I noticed that redundant power supply has specific slot in chassis.

How about if install the only one power supply where redundant power should be installed, Would switch operates?

thanks a lot!

Edison Ortiz Wed, 12/17/2008 - 11:53

That's a good question, ideally when using one power supply, you should insert it on the PS1 slot.

__

Edison.

sarahr202 Wed, 12/17/2008 - 12:26

T hanks a lot Edison for your reply.

But if we don't install the power supply

in p1 slot but install it in p2 slot. would the switch work or generate an error message.

thanks !

shamilton-wilkes Mon, 01/26/2009 - 10:09

Sorry to add to this thread after such a delay:

Just converted a pair of 6509's to VSS at the weekend, one of which doesn't quite have enough power for redundant mode - due to the power reservation for the Redundant Supervisor. But redundant supervisors aren't supported under VSS and won't be for a long time I expect.

Is there any way to remove the reservation?

Actions

This Discussion