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School District WiFi issues - Calling Experts!

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October 27, 2010 2:21:44 PM

So I have a large building made of thick concrete walls. The building is mainly 1 long hallway with classrooms on either side. I did a quick site survey and came to the approximate location needed for each AP to penetrate each room.

I purchased (8) Engenius EAP-9550 APs and (4) TrendNet PoE switches. I ran (3) cables from a single room to the (3) APs on that side of the building (PoE). I sequentially alternated from channels 1-6-11 to avoid crosstalk and named each AP the same. Here is a diagram of the final layout

FINAL LAYOUT

PROB 1) When I try to connect with my phone, laptop, "tech cart", etc, the connection is seen at full strength, but soon after I connect it suddenly goes from great signal to crap. What actually is happening is the device is hopping to another AP down the hallway. WTF. Rather than connect to the strong convienent access point outside the door, it connects to the one down the hallway. They all have the same SSID. I know I can change the preferred order based on MAC, but these are roaming devices and that doesn't work.

PROB 2) I tried renaming all the APs to different SSIDs and the same thing occurs, it decides to hop to a different AP, usually weaker. I've tried different channels, different client devices, etc.

PROB 3) I said, hell with it, and decided to make 1 AP on either side the root and the other 2 APs around it repeaters. This would eliminate the hopping ideally. As soon as I changed 1 AP to a repeater.....EVERY PC in the building popped up an IP conflict error in XP. Is this a bridge loop issue?

ANY help or opinion on this issue would be great! Thanks!
November 4, 2010 3:39:42 PM

Im not an expert just a student tech at university. but we ran into a similar problem with connections in older heavy bomb shelter style buildings. my guess is even though your Access points are able to penetrate the wall(whatever else) your Phone,laptop and other devices don't have the power to. so even though you can hear the AP loud and clear it cant hear you.

you can test this by taking your laptop into the ceiling or wherever you have direct sight to AP. if that is your problem you either have to move the APs' or set up repeaters to broadcast the weak Laptop, phone signals to APs'. so you would probably need some kind of repeater/brige to AP hybrid thing otherwise your just wasting bandwidth. but im sure someones done something like that on here.

Good Luck!

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November 15, 2010 4:03:57 PM
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I also work for a school district and have run into similar issues. I have always used the same SSID name and login credentials to allow devices the ability to "float." Although in our situation, these tend to not move around all that much. Still, I have setup a few AP's as repeaters when I've run into the situation where a device would continually want to attach to one of it's weaker options.

Your repeater idea should work, ideally allowing your roamers to float between points with much more fluidity. As a repeater, it will share not only it's SSID, but also its MAC address, so your devices should see the two (or more) as virtually the same connection.

As far as the problem you mentioned in 3, I would think resetting network connections or simply rebooting each machine should get it a clean address from your DHCP server. Either than, or try changing one of your AP's to a repeater again after school and double check that the repeater settings were made correctly. We use D-Link AP's that come with management software and allows setting up a repeater very easy.

Good luck.
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November 22, 2010 1:36:43 PM

Best answer selected by cpujunky.
November 22, 2010 1:44:07 PM

richpart said:
I also work for a school district and have run into similar issues. I have always used the same SSID name and login credentials to allow devices the ability to "float." Although in our situation, these tend to not move around all that much. Still, I have setup a few AP's as repeaters when I've run into the situation where a device would continually want to attach to one of it's weaker options.

Your repeater idea should work, ideally allowing your roamers to float between points with much more fluidity. As a repeater, it will share not only it's SSID, but also its MAC address, so your devices should see the two (or more) as virtually the same connection.

As far as the problem you mentioned in 3, I would think resetting network connections or simply rebooting each machine should get it a clean address from your DHCP server. Either than, or try changing one of your AP's to a repeater again after school and double check that the repeater settings were made correctly. We use D-Link AP's that come with management software and allows setting up a repeater very easy.

Good luck.



I believe the issue(s) have been resolved.

The IP conflict was indeed a bridge loop issue. Since the repeaters were connected to the network both wirelessly, through the main AP, and through LAN, over the PoE switch, it was causing echos. Turning on 802.1d spanning tree on all devices resolved the issue. Kind of scary...and intreresting...to think you can take a whole network down with a POE switch, a repeater and an access point :) 

I also swapped out the Engenius USB WAN adapters for some basic linksys models. It seemed when the engenius adapters would connect, they would soon start hopping to another access point and somehow mess up the original AP. In fact the AP wouldn't even show up in broadcast until time had passed. No idea what that was about, but alas everything is resolved for now.

Thanks!
November 23, 2010 9:01:47 PM

Glad to hear that your issue has been resolved and i apologise for hijacking your thread to ask a sideways question. May i ask why you used a PoE switch rather than a standard switch? Do you have to? What are the advantages of doing so?

Thanking in advanced,

Steve
November 23, 2010 9:13:25 PM

No apology needed.

The building is primarily one long hallway made up of thick brick (ala bomb shelter). There are no outlets in the hallways and there was no easy way to run power to the individual APs without major drilling or running power cable through a doorway to a classroom in the area. PoE seemed like the easiest choice; running cable from one location over and out of the classroom. Given our budget it was the only acceptable choice. All-in-all, to make the entire school wireless, with 8 APs and 4 PoE switches cabling and raceway, the cost was only about $1200.
November 23, 2010 9:27:26 PM

Thanks for the prompt reply, certainly cleared things up for me. Also working for schools i have been considering wireless solutions. Did you follow a online guide regarding 'site surveying' or was that prior knowledge?

Again thanks for the help.
November 24, 2010 3:37:02 PM

stevetilsed said:
Thanks for the prompt reply, certainly cleared things up for me. Also working for schools i have been considering wireless solutions. Did you follow a online guide regarding 'site surveying' or was that prior knowledge?

Again thanks for the help.


Previously we had placed a handful of cheap D-Link APs in the classrooms. It left a large number of dead spots and teachers often had to take their palm/laptop to a different area within the building to get wireless.

In order to make the whole building wireless, with minimal dead spots, it was necessary to spend some time "surveying" the building. This was the first time I had made such a large building completely wireless, let alone one with some many difficulties.

I read some basic site-survey information online from Cisco, but for the most part I just used common knowledge. I knew the weakest link in the wireless system would be the client device's inability to transmit back a strong enough signal to the AP. I used my HTC EVO, of all things, and a free program called "Wifi Analyzer". I figured if the phone could get a good signal, so could laptops, iPods, etc. The rest was just me dragging an AP and an extension cord around the building and down the hallways. I walked in and out of surrounding classrooms and tested my signal strength. When the strength fell below tolerance, say -85 dBm, I would move to the next AP location.

Worked for me.
November 25, 2010 5:06:46 PM

Superb, i have been using the Wifi Analyzer app in schools for a while now but never thought of its use from that direction. I will give this a go shortly.

Thanks for all the help!
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