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We just took delivery of a new Avaya 2500 48-port switch, that has 24 PoE ports. The problem is that all the PoE ports are on the left-hand size of the switch, and our PoE device cables can only reach the right-hand side of the switch (we're upgrading from an old switch to a new one, and the old one had them on the right-hand side. This is the problem with doing neat cabling).

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Can I just mount the switch upside down? This would move the left-hand ports to the right-hand side and problem solved.

My largest concern is that airflow or cooling might not work, but I can't see any visible breathing holes in the bottom or top of the switch which leads me to believe it will be OK, but better safe than sorry.

Mark Henderson
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    Hi Mark, not sure if you can change your chosen answer after the fact, but I think one of the others should get the points for answering this, not me. My answer was really intended as a bit of fun, not a serious answer :-) – Chris McKeown Apr 30 '12 at 10:42
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    @ChrisMcKeown - I can change it, but it does a good job of answering the question (if you turn your monitor upside down), so why not :) – Mark Henderson Apr 30 '12 at 10:49
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    I would be afraid of the data falling off the cables... :o) – BerggreenDK Apr 30 '12 at 12:51
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    Actually no, but remember to get special drivers to turn the upside down bytes back up. It works, though - I here people in australia install all network equipment upside down. – TomTom Apr 30 '12 at 15:36

9 Answers9

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˙sɯǝlqoɹd ʎuɐ pɐɥ ɹǝʌǝu ǝʌ,I puɐ uʍop ǝpısdn pǝʇunoɯ ǝɹɐ sǝɥɔʇıʍs ʞɹoʍʇǝu ʎɯ ɟo ll∀

(Seriously: you should have no problem mounting a switch upside-down - just make sure you don't create any ventilation issues)

voretaq7
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Chris McKeown
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YES

There is no problem mounting a device like this any way at all -- on its side, upside down, whatever you want.

I have 20+ years of network admin experience, fwiw, and have built and managed many racks of gear.

Jonesome Reinstate Monica
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Yes and I've even had some mounted vertically BUT if the switch (or other device) has a fan such vertical mounting will in most cases cause the fan to fail much earlier because the bearings are not loaded as they were designed to be.

John Gardeniers
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    If fans are likely rear-facing, turning the switch upside down means that they are rotated around their axis. The bearings are rotationally symmetric around the axis of rotation so that shouldn't make a difference. If the fans are horizontal, then we are indeed reversing the axial loading of the bearing. E.g. a CPU fan rests in its bearing, pushing down. If we flip the motherboard upside down, it is then pulling the bearing instead. – Kaz Apr 30 '12 at 19:06
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    I believe such a difference in bearing's load is negligible. – yrk May 01 '12 at 10:52
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    @yarek, the difference between mounting right way up or upside is indeed negligible. That's because the fan's own "down" force ensures the bearing is correctly loaded. Turned on it's side the difference may be small but is certainly not negligible, unless the fan is designed to work that way. – John Gardeniers May 03 '12 at 00:11
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    Have anybody seen a cooling fan with an explicit "up" mark which would designate it is "designed to work that way"? I guess none. Yet, if one's concerned with wearing of the bearings, one could periodically rotate the device to balance the wear – yrk May 04 '12 at 14:14
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    @Yarek, you appear to have misunderstood the something. The wear issue occurs when a fan designed to run with the spindle vertically is operated horizontally. – John Gardeniers May 04 '12 at 22:17
  • @JohnGardeniers what i'm trying to bring here is if there is a wear caused by such an "inapropriate" mode of operation, it is negligible. My last post is meant to appear sarcastic. – yrk May 04 '12 at 22:24
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All of things considered equal it shouldn't matter.

I do have one word of caution for you though. We are in the middle of upgrading all of our switches to new Avaya switches across our campus. We installed two new switches in a cabinet in one of our buildings directly over the existing switches and immediately had heat problems with the new switches. The switches would trip the thermal protection after only about 30 minutes and shut off. We made some modifications to the closet they were in to cool it down and that did the trick for the most part, but the fans still sounded like they were going to take off. We left them like this for a couple days to make sure they would survive and they did.

The switch over came and we moved the cables from the old switches to the new switches and shut off the old switches. Within 10 minutes the fans quieted down so much that we thought the switch shut off. It turns out the old switches exhausted on the left side and the new switches had the intake on the left side. So the new switches were taking the hot air from the old switches and were not able to cool themselves effectively. Not saying this will happen if you mount them upside down, but it is something to watch out for.

johnny
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PlTaylor
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There are usually no problems with doing that, but be careful about the fans (if there are any). Fans will probably have a shorter lifetime.

Another problem is the dust, collecting in places where it otherwise wouldn't.

Even if you don't care about fan lifetime, i would still check for dust residue after some time, since it will fall to the "wrong" side, and won't get blown out by the fans. (Of course, there shouldn't be a lot of dust in server rooms, but still...)

John Gardeniers
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mulaz
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  • Are you implicitly combining two types of fans in your answer? Dust removal should be handled primarily by fans on the back by fans mounted perpendicular to the mainboard. Flipping the entire unit 180* shouldn't affect their loading in a meaningful manner. The fans that might be sensitive to being flipped would be those mounted parallel to the board that are blowing down on a specific chip's heat sink. – Dan Is Fiddling By Firelight Apr 30 '12 at 13:02
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    Yes, but the dust should be falling towards the "bottom" of the switch, and the fans blow the dust from there. It all depends on the hardware design, and if the fans go all the way from-top-to-bottom. These fans lifetime will not be affected by the rotation, but their "dust-removal-capabilites" could be. – mulaz Apr 30 '12 at 13:11
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    I don't think I've ever seen any 'thin' devices (the only exceptions I can think of being desktop/tower style PC cases with fans mounted above the IO panel) that didn't have fans sized to fill the entire vertical area of the case. With larger fans being much more efficient at moving air I'm mildly surprised that small higher RPM fans would be preferentially used anywhere. – Dan Is Fiddling By Firelight Apr 30 '12 at 13:33
  • Okay, a switch can be a bad example, but some devices are build asimetrically. For example google search appliance ( http://img12.imageshack.us/img12/1987/1856442.jpg ) has air intake holes that go a bit under the case, which is fine, if turned right-side-up, but more dust can fall in if turned upside-down... but even this is a bad example, since it's an intake and sucks up alot of dust anyway. – mulaz Apr 30 '12 at 13:40
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    @mulaz, you appear to have dust issues. That's definitely not the norm for server rooms, where we take steps to keep dust levels very low. – John Gardeniers May 01 '12 at 21:33
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The only issue I could possibly see is with airflow and you seem to have that covered, at least externally. Unless the router manual specifically recommends, (or warns against), a particular orientation, then you should be fine, especially in a rack with a fan tray.

I have often had this problem with cabling, well, actually, with skilled wiremen. I can understand professional pride in their work but, especially on non-production specials, precisely trimmed, terminated and anchored cabling does not help. It doesn't seem to matter what instructions I put on drawings, ('IMPORTANT - leave at least 300mm of slack in all cabling, do not use cable ties'), I get racks delivered that look immaculate and then I have to cut all the cable ties and extend the cables because my drawings were wrong, the design has changed, something..

Martin James
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No problem. Typically fresh air suction is from front and hot exhaust are always from rear.

But always check the vendor installing instruction. For some model (e.g. http://www.cisco.com/en/US/docs/switches/lan/catalyst2960c_3560c/hardware/installation/guide/higinstall.html) upside-down installation under the desk is explicitly allowed.

Alessandro Carini
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    Actually, it looks like fresh air comes in from the left and leaves on the right. As one of the previous answerer mentioned, they had an issue where their rack was cooler on one side than the other, and the switch was drawing its air from the hot side. But thanks for the Cisco link. – Mark Henderson Apr 30 '12 at 20:33
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I've encountered a situation about a year ago where I placed a Cisco switch on it's side (wedged between two stacks of desktops acting as an experimental Hadoop cluster) assuming it wouldn't matter.

For some reason the switch didn't work at all. As soon at I placed it upright again it worked like a charm.

As far as I can tell it had some kind of orientation sensor (perhaps as simple as a mercury switch) that caused it to "not work".

Apparently the designers of that thing had a good reason to invest in adding a sensor to avoid this kind of positioning.

So instead of a plain "yes" or "no" answer I'm saying it depends on the actual device at hand.

Niels Basjes
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This is quite a bit late of course but the only major issue, and it could be major later on, is when a newbie is helping you and they go to what is logically port 1 and instead remove the cable from port 48 because they didn't read the numbers but are used to ports numbered left to right. When side mounted on a wall, people always think, "check which port I am grabbing". But when mounted flat as "should be" then they think it is as "should be".

So, to play safe with idiots, install it right side up and recable.

Allen McEuin
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