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Anyone experience with PoE adapters??

Dec 31, 2007 6:23AM PST

I do some volunteer work in our local school....(low budget/not budget) and we're looking at ways to use the existing infrastructure rather than do extensive rewiring. Going fully wireless is not a possibility at this time, however. Two things we need to do are to add a few more ports to classrooms. Currently each room has only one or 2 wired ports. When extra connections are needed, it's necessary to carry a small switch or hub into the room just to add a couple of connections. My thinking is that, with PoE we can just use something like a 3Com Intellijack system where needed but our 3Com baseline switch doesn't have PoE capability and this is pricey hardware if you just need a limited number of powered connections. Another use for PoE would be to add a couple of PoE capable wireless APs for use with a mobile laptop cart. This cart carries about 2 dozen laptops to the various classrooms for specific projects. It has it own AP but must occupy a network jack to work. It's a 2 story school building so we'd need to figure out what it would take to cover the whole building. It would seem that eliminating the need for DC converters and using a lot of AC outlets would be worthwhile. There are PoE "in line" adapters available that we could install in the network cabinet just for the Cat 5 that needed power. I am wondering what the downsides might be to doing such. Is PoE hazardous to network health in any way? TIA

Discussion is locked

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"Is PoE hazardous"?
Dec 31, 2007 8:18AM PST


But if you are under a tight budget I'm unsure how it could save you any money.


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It's a complicated issue
Dec 31, 2007 10:41AM PST

We've a church school that can get some public money for the hardware but use of that money is restricted and what is purchased becomes public school assets and has use restrictions as well. It's in the school's interest to have ownership of as much of the network as possible. Completing the next phase to improve the network would require either some rewiring or the use of existing wiring to handle more connections. I can calculate a need for at least 2 1000' spools of Cat 5 (or 6) plenum rated cabling plus the assorted connectors. As well, the existing patch panel is maxed out and we'd need an additional one. A simple solution would seem to be to add hubs/switches as needed but another issue in this old building is electrical outlets. It was never wired for this electronic age. Every outlet is precious. We already have so many power strips and extension cords around that the every fire inspection is a panic situation. We've been able to have some rewiring done but the job is far from complete. Meeting new codes is expensive. The computer lab which houses the network cabinet has plenty of juice and the networking hardware is on a UPS. The eventual plan will be to make the school into a secured "hot spot". This won't eliminate the need for the existing wiring which is only Cat 5. Any rewiring should be, I would think, Cat 6. Because the computer lab has no power shortage, it would seem that considering PoE for some of the expansion is workable as long as we can't expect ill effects such as speed loss or damage to connected components. Powering wireless APs, range extenders, or whatever we will need seems like reasonable idea if it will be neater, save electrical outlets and not have a bunch of hubs and AC/DC converter bricks all over the place. I appreciate your thoughts about the costs. I will have to get some good numbers but, in my experience, cheap doesn't always mean inexpensive. Thanks.

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an odd thought
Dec 31, 2007 2:02PM PST

Why can't the existing wiring be turned into one large antenae system which would reach each room and have the wireless server in the central location? All computers would go to wireless.

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Can't go wireless just yet
Dec 31, 2007 9:37PM PST

Within the past 2 or three years we've scraped up enough to replace all the aging lab PCs and classroom PCs with P4s using XP Pro. We'd need wireless NICs for a couple dozen PCs...$$$$$..The network has no dedicated server or authentication device..$$$$$. That would be a nice addition.....something like active each user could be separate. As it is, we are divided only by "group". My wife is the "network administrator" so to speak. I'm just the lowly hardware guy with limited experience. Neither of us are that network savvy.

There are many pieces of equipment paid for with public money such as "smart boards", a NAS, networked printers and some really nice distance learning equipment. It's all wired. There is a laptop cart with a mix of wireless a b/g computers. The cart's AP only handles 802.11a and was purchased with public money. We've some donated 802.11.b/g rigs that I need to get on the network. Ideally, I need a dual radio system to handle all of them but these are pricey in comparison to "g" only. The complex issue is that anything we pay to fix that was purchased with public money....and there's no law against money lost. The wireless "a" laptops need to be used until they die and not put a dime into them. Once dead, they are returned to the public school system and replaced with more current technology and I'd want to spend money for wireless that accommodates currently used technology only. The laptops are the only roaming devices now and most of these are older "a"s.

We have a couple of classrooms that I ran out of Cat 5 before I could add a second cable drop. I wanted to keep a port open for special use and not have to install hubs every where. These are the classrooms farthest from the relay rack. Cat 5 plenum rated cable runs about 20 or so cents per foot and you only get a deal buying in bulk. With PoE, I can turn 1 port into 4 for about 150 bucks without having to crawl through the ceiling with wire between my teeth again. Happy The downside is that it tends to drop the speed from 100 to 10 mbs. This shouldn't be much problem though. I'd be able to add wireless radio devices strategically to cover the school area for students and staff with their own laptops as well. It would seem that limited PoE for now might provide a bridge to get us through until a fully wireless environment is feasible and affordable.

James, I appreciate the thoughts of anyone here. I'm just studying up on this stuff. I'm not a network guru and just learn as the need arises. It's also fun stuff and more enjoyable than my real job. Happy

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802.11a explains so much.
Dec 31, 2007 11:07PM PST

When I see that I find some committee mentality. These enterprises lurch from committee decision to the next with big failures. It's sad to see yet another dead technology being considered when just a good network guru could start slowly sorting it out with readily available and cheap compared to 2 years ago gear.

But you are a victim of the work/school environment so it may be best to not buck the usual trend and lousy implementations that such environments tend to create.


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I don't envy your dilemna
Jan 1, 2008 10:24AM PST

Have you considered a 100 piece drop shipment of USB or PCI wireless devices from a wholesale supplier, perhaps from Tawain?
Try or others.
For instance, here's one you could probably bulk order 50-100 for half the price of this retail version. Here's a USB wireless fob that I've seen sold at various online retailers here in US, usually has a Zydas chip in them.

I'm thinking you could buy in bulk for less than half the price of retail, even after shipping is included.

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thanks for the's the issue with cheap
Jan 1, 2008 8:05PM PST

We've been that route. Because this is all volunteer and time is limited. We don't need a lot of stuff that needs support. We had to stop taking donated old PCs such as Dells. It took up too much of our time with the care and feeding of them. There's no rush to wireless here but it would be nice to be more mobile with the laptops and not need them tethered to the cart to work.

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The advantage of...
Jan 1, 2008 9:27PM PST

...a drop shipment of exactly same equipment over donated and used items of differing manufacturers and suppliers is you need only the same support for each and everyone of them. Having wireless devices from 10 different suppliers will be a bigger headache than having them all from the same running from the same driver files. I'm not saying those particular examples are what you would get, but linked them so you could consider the possibilities. The reason I mention the USB devices is they can be gotten for under $5 each on drop shipments, of course the downside is those tend to "walk" unless there's an internal USB plug, but probably walk no quicker than a PC card on laptops.

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Maybe worth considering later
Jan 1, 2008 10:06PM PST

You're right about USB devices walking. One of the things the school considered was to provide a few USB flash drives for group projects. That these would disappear was a concern. Many of the kids already have their own now so it's not a issue. But, my purpose for asking about PoE was to allow placement of hardware connected to the network rather than add wireless to existing PCs. The laptops all have wireless capability but need to be within proximity of the cart (which houses the AP). The cart's AP is only "a" but some of the newer laptops are b/g. I could find a dual radio box for the cart but that would seem a waste. It would make more sense to me place APs or other necessary hardware in the proper locations to make the whole building available to wireless devices. I just don't want to deal with the clutter of more hubs and power supply bricks. If need be, I can run 3 or 4 cable drops for dedicated PoE devices. That's starting to look like a reasonable choice if they work well and don't mess up anything else.

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different approaches
Jan 1, 2008 10:43PM PST

There's more than one way to do something, that's for sure. I guess it comes down to cost and what you are comfortable with doing. For those reading the thread, here's a quick read page about PoE.
If it was me I'd probably daisy chain some wireless access points using the existing cable in your situation, which I think the PoE is basically doing the same other than also adding more electrical energy to the line, but you've also mentioned the need for more electrical connectors so maybe PoE is what you want. Have fun.

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"That would be a nice addition.....something like active di"
Jan 1, 2008 10:46PM PST
"That would be a nice addition.....something like active each user could be separate."

you do know a wireless router can be set to AP isolation which accomplishes the same?
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Perhaps my use of "active directory" wasn't accurate
Jan 1, 2008 11:52PM PST

but not sure what a wireless router would add. The dream would be to turn the place into it's own domain but that's not in the near future. It would be nice for every kid to have a username and password authenticated account but that means more $$$$ for software and licensing. The network runs XP Pro as peer to peer. The only file server is a NAS device with XP embedded that has a 25 user limit. It does allow students and teachers some private and common space that can be linked to their desktops when they log on to a lab or classroom PC. The 25 user limit allows privacy to individual teacher's stuff but the students are sort of all placed in the same basket. They can create their own folders but can't secure them from other students. The NAS does allow anyone to sit at any workstation and easily find their work in progress but it also lets others find it as well. Of course, being a church school, this shouldn't be a problem...right? Happy

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"that means more $$$$ for software and licensing." Not?
Jan 2, 2008 12:12AM PST

We implemented this with Linux. I wonder if an upgrade to the IT staff would help here. If you look over this post it appears that the site is suffering from committees and some less than stellar IT staffers.


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No committees and no IT staff
Jan 2, 2008 12:57AM PST

No paid IT people at all. It's more a family affair that runs on a wing and a prayer and the trust of the school principal. But if you'd call me and my wife the IT staff, I'd surely plead guilty to its being "less than stellar". Happy

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When in that situation...
Jan 2, 2008 1:02AM PST

You find talent. Today I find a lot of willing helpers that are linux savvy...

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AP isolation
Jan 2, 2008 12:43AM PST

What it does is make each wireless user unable to directly contact or see each other wireless user, but all resources on the wired portion of the LAN are still available.

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secured folders in XP
Jan 2, 2008 12:54AM PST

You can create and share a folder for each student on an XP computer where each folder will have it's name, it's network identity which could be each student's name, and each folder have a different password. You give each student his password to the folder shared under his name. That simple. The downside is I don't know of any way to limit folder size in XP for each student, which is where running a Linux server as Bob suggests works out better. XP does have the ability to set quota size on volume usage, but I'm not sure if assigning a drive letter to each shared folder would cause that to work. I think they have to actually be separate volumes, which is unrealistic for a student body. Maybe Bob knows of some way to limit shared folder sizes. I can see where some student could stuff a drive by overfilling his shared folder. Technically you could create enough network volumes so each student could have done, but I've never tried it and don't care to either. Using a server with assigned FTP accounts would work MUCH better.

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The desire is not to keep data
Jan 2, 2008 2:31AM PST

on the individual PCs at all. That's something we needed to get away from because stuff was getting lost or out of sync. Students need to be able to access their individual work and group projects from classroom PCs and the lab PCs and this is why we thought something in the way of a file server would work out. The NAS has worked out so far but I don't think its version of XP allows individual passwords to be created for each folder within a share. I'm fairly sure it allows quotas, however. The NAS device is an experiment at this point. We know it's a piece of hardware that won't last forever and using it does allow students and staff the see what works and what needs improvement. Bob mentioned the Linux server. I don't think it's a bad idea but I don't know how to set it up and teach its use. As well, someone's going to have to serve as administrator and provide ongoing support. Students are a transient group and their annual migration has it's complexities. Right now we only deal with 4 or 5 workgroups and students are only divided by their grade. Make them all individuals and the work multiples dramatically. But, at least with volunteer work, you've got job security.

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Jan 15, 2008 9:37AM PST

Depending on your port requirements, this is what you need to put in between your baseline switch and the IntelliJack Switches.

I'm sure CDW or your local 3Com rep should be able to get you one at a discounted rate. They can also offer good leasing options.

The 3C number is: 3CNJPSE24

Also, you should contact your local 3Com rep, and talk with them.
Here is a link to find a rep in your area...