How to make a Cisco 2924M-XL Switch silent


Copyright (c) 2005 pa4wdh.
Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.2 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license is included in the section entitled "GNU Free Documentation License".

Legal stuff (Disclaimer):

The use of anything on this page is on your own risk. I thing this will definitely void your warranty. Doing thing wrong, might break the switch at. However, everything here is tested on my own hardware and worked unless stated otherwise.

1. Introduction
1.1 Hardware
1.2 The problem
2. Solving the problem
2.1 What you need
2.2 What you need to modify
2.3 How to install
2.3.1 Opening the switch
2.3.2 Installing the stuff
3. To-do's
4. Contact me
5. GNU Free Documentation License


1. Introduction

Some time ago i bought myself a Cisco 2924M-XL Switch. Not for study, but to power my own network. It simply has features a normal consumer switch doesn't have.
Many people seem to like Cisco's for their home networks, but there's always a problem: Noise. Cisco's are made for professional use in a datacenter, in that case, noise doesn't matter, but for home use, it does.
Last but not least, i would like to say that i don't know if this has any effect on the switch's behaviour, so i won't recommend using this to silence your cisco's in datacenters or other mission critical situations.

1.1 Hardware

In my case, the hardware is a Cisco 2924M-XL with an extra 2931-XL card in it, which allows me to use a GBIC for a gigabit connection. This gives the switch a total of 25 ports. The switch is 2U (Two 19" units) high, which is twice as high as a normal one. This was also the reason to choose this one: More space to put some extra hardware in, and the fan's are bigger. Bigger fans usually means less noise ... usually, because cisco used very low-budget fans. This one to be extact: Delta Electronics DFD0612H

1.2 The problem

As you can guess, the problem is noise. The noise comes for 100% from the fans, because for the rest the switch has no moving parts. Obviously, Cisco over-did the cooling aspect of the switch. The switch only consumes about 20-30 Watt (instead of about 200 what Cisco qualified them for), so to solve the problem all we have to do is make the cooling more silent, but we can't turn it off.

2. Solving the problem

In this chapter you will find all the information you need to make your switch more silent. The solution will be to make the fan speed adjustable (and so the noise)

2.1 What you need

My swhich has three fans, so i use three of these: Zalman Fan Mate 2
Don't worry, they are cheap (4 euro's a piece), so if you can buy a Cisco switch, this won't be a problem.
I also use Sharkoon Rubber Bolts. I couldn't find them at sharkoon's site, or in a review, so i don't have a link. They replace the standard bolts you use to mount the fans in the case. A set consists of 4 bolts, and in the switch every fan is mounted with two screws. The third fan can't be removed, to one set is enough to get the two fans done. The purpose of this, is that the fans are mounted, but the bolts keep them about 1 cm from the case. At the first place this is used to stop vibration from the fan to the case, but it's also usefull to get the wires from the Fan Mate 2's to somewhere outside the switch, so you can adjust the speed whenever you think you need without opening the switch.

2.2 What you need to modify

The installation of the Rubber bolts should be fairly straight forward, but the Fan Mate 2's have a problem: The Fans in the Cisco switch have only two wires, while the Fan Mate 2 is made for 3-wire Fans.
From the specs of the Fans and the Pin-Out of a three wire Fan connection, you can see that we need to swap the + and - wires before we can use them.
I strongly advise to replace the connectors at the Fan Mate 2 with 2 Pin versions, but if you don't want to do that, you can also modify the Fan Mate 2's cable.
The best way to do that is at the connector that goes into the Fan Mate 2 itself. At each side of the cable, you will find a red and a black wire. Simply change the red and black one at each side. You can easily get the wires out with a small pointy tool, i used the probes of my multi-meter. Just push the white locks up a bit, and pull the wire.
On the male connector, also break away the white part that normally locks the connector in place, because it will make it impossible to connect the fan.

2.3 How to install

This paragraph will tell you how to actually install everything.

2.3.1 Opening the switch

The switch is quite easy to open, if you know how. Ofcourse, first remove all the screws that hold the cover in place. After that, get a flat screwdriver and put it in the small opening on each side, just behind the front. Turn the screwdriver 90 degrees, and repeat that on both sides until the cover doesn't go back further. Now remove the screwdriver, and grab the cover at the back side, and pull it back and up, and the cover will go off.
Warning: With the switch wide open, there is also no protection between you and the power supply, and the mains voltage is also running there. Be carefull when handling the switch with the cover off and connected to the mains power.

2.3.2 Installing the stuff

Remove the screws that keep the fans in place, and disconnect the fans. Now connect the Fan Mate 2's to the connectors where the fans where conected to. Make sure to connect in such a was that the Red and Black wire are connected, not the yellow.
Now connect the fans to the Fan Mate 2's, and again be sure to connect to the Red and Black wire (note that the colors do not match). Now make a test-run, each fan should operate, and should be controlable by a Fan Mate 2.
Now turn the switch off again, and run the Fan Mate 2 wires through the holes of the fans, and install the fans again with the Rubber bolts. Test-run again, because if it works now, you can put the cover on again, and enjoy your silent switch.

3. To-do's

Things i think i should change to this document:
Add pictures to make sure everything is clear
Add some suggections on how to set up the Fan Mate 2's
Add temerature measurements with and without the modification.

4. Contact me

Suggestions, reports and comments are always welcome, if i have time i'll test it on my own systems before i pubilsh it on this page. If you want to contact me, you can send an email to pa4wdhNOSPAM-at-yahoo-dot-com (Remove NOSPAM, and replace -at- and -dot- with a @ and .). Please help me to organise my email, and put the word cisco somewhere in your subject line.

5. GNU Free Documentation License

The full text of the GNU Free Documentation Lincense can be found here.

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