Requirements for multiple APs sharing one SSID

Posted on 2013-06-27
Last Modified: 2013-07-26
Imagine a small network, 10-20 computers, and they are spread out over several floors of a building.

Typically, to get good wireless coverage on all of the floors, I'd put in three access points - one on each floor. The APs are connected via ethernet cable to the switch, which is connected to the router. The APs all have the same SSID and security/encryption configuration, but use different channels.

The thing is - cheap routers or access points don't tend to do this properly. For example if you buy 3x WRT54G routers, turn off the NAT/router/dhcp, and use them as wireless APs, they'll confuse each other and NO computer will connect successfully to any AP at all.

If I use something "good" - generally I put in an Engenius EAP350 APs, then everything is fine, the APs can co-exist together and everything works great.

So my question is - is there some kind of determinableFEATURE of the access point that it needs to have in order to support this configuration of multiple APs with the same SSID?  Is there some portion of the 802.11 spec that I can check that it supports, or something else?

Is there a strict requirement that all the APs be the same make and model? Can it be a mixed environment?

Basically, how do I differentiate between a "cheapo" access point that won't support multiple APs with the same SSID, and a "good" access point that will?
Question by:Frosty555
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Accepted Solution

iconnectu earned 500 total points
ID: 39283796
The cheap routers are made for stand alone and home use ONLY. The power is set to 100%, that means that the routers don't sense, what actually is needed by the clients -> The idea is to cover a hole household with only one device (Home network).

For business, this is not useful. You need some intelligence on the AP's that they can communicate and see each other. They automatically sense the signal strength needed by the client and neighbor AP and reduce it to a minimum, to not interfere with other WIFI AP's. Business AP's also support Roaming. This is really important when users move around with there mobil-phones and notebooks, to not loos a skype or VoIP call.

Also important is managing and monitoring. Instead configure 20 cheap Netgear Routers manually one by one, business AP's like the Ubiquiti UniFI or Aruba have a centralized Management. You configure one and adopt the other 19 AP's with one click to the network. auto-provisioning, firmware-updates, guest access, Multi-SSID's, VLAN's - you can't build that with Home equipment - with Business products, this is only a few clicks away.

It's is just a recommendation, but don't use home equipment for business customers - even when there is only one computer to connect with.

Ubiquity UniFI AP's start around 120$ Enduser price. They are cheap, but have all the features needed to build fast networks with all the features business customer request and need.

Check out:
LVL 31

Author Comment

ID: 39295383
iconnectu - I appreciate what you're saying, and I agree that the management, monitoring, and automatic provisioning capabilities of a real enterprise-grade wireless network is very valuable to a customer who is really depending on the WiFi to work. For these customers there's the Ubiquity UniFI, Cisco Aironet, Meru Networks, etc., networking equipment with a central "air traffic controller" that can manage, provision and monitor the various APs.

And I guess my original question did make it seem like I was talking about a mid-size business that would need that sort of equipment... but in reality I'm dealing with smaller fish e.g. a tech-enthusiastic home network or a home office. Imagine a "big" home that consists of a family of 5 each with a laptop, smartphone, tablet, a couple of gaming consoles and desktops kicking around. They need 2 or 3 access points to get full bars on both floors of the house and outside on the patio.

I've had success with various combinations of the following equipment:

   - Engenius EAP350
   - ASUS RT-N16 running Tomato Firmware
   - Linksys RV120W
   - Apple Airport Extreme

And I have seen it consistently fail when I use the following:

   - Linksys WRT54G
   - Linksys WAP54G
   - DLink DIR601
   - Most gateway/router/modem combo devices that are provided by an ISP
   - Generally any consumer router that costs <$60

Even if in this smaller scenario you'd still deploy Ubiquity equipment, it's just sidestepping my question, which is what is the difference between, say the Engenius EAP350, which is a stand-alone wireless access point and works great, and the WRT54G which is a standalone wireless access point and fails? Is there a way for me to tell which access points can support multiple APs sharing a single SSID, and which ones won't?

Assisted Solution

iconnectu earned 500 total points
ID: 39295741
If i have to use equipment for home-use, i take the Apple line (Timecapsule, Airport etc.) for Apple PC's and small Cisco Routers, APs and devolo dLAN devices for Win PC's.  

The Problem that this devices are not working well with each other is, that WDS (Bridging from one AP to another) is not really a standard and every vender handle this protocol different, channel mismatch (both APs on the same channel) or one AP is set to TKIP, the other use AES for encryption.

BDW: Bridging is not the best way to cover bigger households, because it sloes down the network. In this cases you better go with some devolos dLAN devices.
LVL 31

Author Comment

ID: 39302459
Hi iconnectu,

I agree that WDS isn't a good way to go - it unnecessary chews up wireless bandwidth for use as your backhaul instead of using that bandwidth to communicate with clients. Besides that... positioning of the APs is pretty critical, since they need to be close enough to a neighbouring AP that they can communicate, but far enough away that it is actually extending the range of the wireless somewhat.... it's a messy and flaky way of doing it and I think that's basically the concept behind "wireless repeaters / extenders". I never do it.

.... in my case the access points are always connected to the network with an ethernet cable, they are not using WDS.

Or is there something about WDS I'm not understanding?

Again, I'm not looking for suggestions on what devices to use. I'm looking for information on why some devices do not interoperate together properly.

Is this concept of having multiple APs sharing the same SSID part of the 802.11 spec? Is it that this is a vendor-specific functionality and that's why some devices don't play nice with each other?

Assisted Solution

iconnectu earned 500 total points
ID: 39306546
The thing's i see, is that some brands don't play well with apple computers. Zyxel is such a vendor. From the smallest to the business APs, you will always have problems with it.

For shure, some venders will have there own protocols to implement features, that are not clearly specified in the 802.11 specs, like WDS. But, the most time, i have trouble with multiple APs is because of channel overlapping or microwave, Bluetooth or Dect senders.

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