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redundant power supplies for cisco 4500,6500 switches

Hi every body!

I have few questions about the power supplies for 4500,6500 series switches.

1) Both 4500 and 6500 cisco switches support upto 2 power supplies.Are there two power cords, one for each power supply?

If there are two power cords for two power supplies in the chassis, we need two AC outlets to connect them. Am i correct?

2)What determines which power supply in the chassis is designated as power supply #1 and power supply #2?

thanks a lot!

2 ACCEPTED SOLUTIONS

Accepted Solutions
Hall of Fame Super Blue

Re: redundant power supplies for cisco 4500,6500 switches

Sarah

1) yes there are

2) You could connect them to the same power supply but that wouldn't be a good thing to do. You would want separate power supplies for each.

3) Not sure to be honest. I always assumed it was the left hand one as you look at the back of the chassis.

Note that for the power supply to be truly redundant you need to make sure that one power supply has enough to power all the modules/devices in your chassis - this is known as redundant mode. This can be especially important with PoE devices. You can run the power supplies in combined mode where the power needed for the chassis is more than one power supply can handle but then obviously if that power supply goes you lose some functionality on the switch.

Jon

Hall of Fame Super Blue

Re: redundant power supplies for cisco 4500,6500 switches

No problem with repeating question, it was probably my poor explanation.

I have seen a 6500 with redundant power supplies with the 2 power leads connected into the same extension lead. This kind of defeats the purpose of dual power supplies.

What we did in our data centres was to have completely separate power supplies coming into the DC and each rack had a connection to both supplies. Then we connected one 6500 power lead to one of the power supplies and the other power lead to the other power supply.

Does this make sense ?

Jon

4 REPLIES
Hall of Fame Super Blue

Re: redundant power supplies for cisco 4500,6500 switches

Sarah

1) yes there are

2) You could connect them to the same power supply but that wouldn't be a good thing to do. You would want separate power supplies for each.

3) Not sure to be honest. I always assumed it was the left hand one as you look at the back of the chassis.

Note that for the power supply to be truly redundant you need to make sure that one power supply has enough to power all the modules/devices in your chassis - this is known as redundant mode. This can be especially important with PoE devices. You can run the power supplies in combined mode where the power needed for the chassis is more than one power supply can handle but then obviously if that power supply goes you lose some functionality on the switch.

Jon

Bronze

Re: redundant power supplies for cisco 4500,6500 switches

Thanks Jon!

I am sorry for repeating my 2nd question.

2) If there are two power supplies, are there two power cords , one for each power supply. If yes, it means we need two AC outlet two connect them?

your answer:

"You could connect them to the same power supply but that wouldn't be a good thing to do. You would want separate power supplies for each".

I am still confused how we can connect two power cords to same power supply.

you mean each power cord form each power supply is connected to sepeare AC outlet.

Did I understand you correct?

thanks a lot!

Super Bronze

Re: redundant power supplies for cisco 4500,6500 switches

When you use two power supplies in redundant mode, you're trying to avoid a single point of failure. If you connect both to the same AC circuit (very likely if you connect them to the same outlet), and something like a breaker pops, you'll lose all power, so you ideally want to connect them to separate AC circuits. If the latter can't be done, you're still protected if just one power supply in the chassis fails.

Hall of Fame Super Blue

Re: redundant power supplies for cisco 4500,6500 switches

No problem with repeating question, it was probably my poor explanation.

I have seen a 6500 with redundant power supplies with the 2 power leads connected into the same extension lead. This kind of defeats the purpose of dual power supplies.

What we did in our data centres was to have completely separate power supplies coming into the DC and each rack had a connection to both supplies. Then we connected one 6500 power lead to one of the power supplies and the other power lead to the other power supply.

Does this make sense ?

Jon

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