OK to use WDS with access points plugged into LAN?

257Roberts
257Roberts used Ask the Experts™
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I have 4 D-Link DWL3200AP access points.  I have two of them in WDS with AP mode now. One is plugged into the  wired LAN and the other that is in WDS mode is in a remote building 200 feet away and just grabbing the signal from the other one.   I am adding one more access point and wondering if maybe now would be the time to configure all of the access points in WDS mode.  All of the remaining AP's would be plugged into the wired LAN.  It would be nice to have them all on the same SID, because now we are using three different SID's.  If AP's are in WDS with AP mode is it okay to have them plugged into the wired LAN?  Thanks for your replies.
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If they're all wired in, WDS should not be needed. Just set them as APs on the same ESSID, using channel 1, 6 or 11 to keep them from interfering with each other. Actually, with the same ESSID and on the same channel, they should take turns gracefully according to the 802.11 spec.  But it will lower bandwidth slightly (because they're taking turns on the same frequency).

WDS isn't really a standard (like 802.1x authentication, 802.1q VLAN tagging, et cetera)... It's just a way for them to talk to each other, and since it's not a standard, pretty-much all of the manufacturers make them so they'll talk to only the same brand (D-Link units connect only to other D-Link units; Linksys connects only to other Linksys - sometimes not even to different models; and Cisco has a completely different definition of WDS).

WDS 'kind-of' secures the access, but it does not secure data exchanged between them, since all the implementations I've seen would use only WEP encryption. Meaning anyone within range can capture the data and decrypt it (WEP can be broken in less than 10 minutes with freely-available software) at their leisure.

Author

Commented:
Thanks Darr for the reply, but I will still need one of the access points to be remote, not wired in.  Would I keep that AP and the one it grabs the signal from all on the same channel as the others and the same overall SID?  Also, if I understand you correctly you are saying with the others that are wired in, I can use one SID for those as long as I use the same channel? Thanks for your reply.  

Author

Commented:
By the way, your explanation of WDS and lack of manufacturers standards was helpful.
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> Would I keep that AP and the one it grabs the
> signal from all on the same channel as
> the others and the same overall SID?

It MUST be on the same channel and SSID as the one with which it's communicating in WDS mode.
Whether those 2 are on the same channel as the others depends on many factors.  If on the same channel and they can 'hear' each other, then they *should* use the same SSID or they'll interfere with each other... when they use the same SSID and they're on the same channel they should take turns rather than interfering.

If using different SSIDs on the other APs, then they should definitely be 5 channels away if they can 'hear' each other.

The exception to that is when using multiple SSIDs on the same AP... in that situation it won't/can't interfere with itself because it won't be talking on multiple SSIDs simultaneously (it might *look* like it is, but at < 500 microseconds per transaction, it can switch back and forth between two SSIDs and send/receive 1000 packets to each of them per second).

Have you done a walk-around with a laptop using software like inSSIDer from metageek.net, to see what kind of range you have from each AP? The DWL-3200 has a site survey in their setups, too, if I recall correctly... at least in the browser menus. Are you using the web interface or the AP Manager software that D-Link provides?

Using non-overlapping channels when the APs can 'hear' each other allows each to use its full bandwidth... if you have 3 APs in a room on the same SSID and same channel, with clients connected to all of them, each will have a theoretical maximum bandwidth available of about 18 Mbps and they will take turns... before each one transmits it listens and if it hears another station talking it backs off and waits a random time. If you have 3 APs in a room on the same SSID but using channels 1, 6 and 11, each one will have its full bandwidth of 54Mbps available. If you have 3 APs in a room on the same channel but different SSIDs, none of them will be able to talk (about the time you get connected one of the others will interfere and cause the connection to drop), because when each does its pre-transmit 'listen' they hear *something* but since it's not the same SSID it's just babble. Still, a lot of times the full bandwidth isn't required... are you streaming video, sharing files/printers, acquiring I/O status from machinery, point of sale <-> database/accounting?


> Also, if I understand you correctly you are saying
> with the others that are wired in, I can use one SID
> for those as long as I use the same channel?

Well, I'm sorry you inferred that, but that's not exactly what I meant... I regret my lack of clarity.
If you want to enable roaming they all need to be on the same ESSID; If roaming is not needed (or even desired), then using different ESSIDs doesn't 'hurt' anything, as long as they're not competing for the same channel; If within range of each other and using the same channel, they *should* use the same ESSID or they could interfere with each other; if within range of each other and you need/desire different ESSIDs, then place them 5 channels apart to prevent overlap interference. 1, 6 and 11 are the channels I recommend using in the americas (in europe they can use 1, 5, 9 and 13, lock them to G-only and avoid overlap interference; if they need 11b compatibility then they should use 1, 6 and 11 also).
ESSID = wireless network 'name'
BSSID = The AP's MAC address

I've been trying to always use ESSID when talking about the wireless network identifier, but sometimes I forget.

Author

Commented:
Thanks Darr,  I would like to enable roaming between the AP's that way the users only have to to remember one ESSID and passkey.  I will do a wireless survey tomorrow if the extra AP's I am installing are shipped to me.  I am just using D-Links web interface.  I think I remember getting AP Manager software in the boxes, but did not want to pay for anything extra I would not be using. I am running DHCP and DNS on a Windows server.  Do I still need to put the default gateway address into each AP configuration?  The default gateway is a SonicWall box.

Are you saying that the AP's that will need to be in WDS mode cannot use WPA-Personal encryption?  I thought I had them all set up using WPA, but maybe not. If the two in WDS mode are using WEP can the others use WPA if they are on the same ESSID and channel?

 I work for is a large church.  I begged them to wire all clients, but it is an existing building and must be too expensive to retrofit using wired Ethernet.  The users do mostly email, printing to two large copiers and internet surfing.  

With your advice, I am planning to have all AP's with one ESSID and put them on one channel. Maybe channel 11.  Thank you so much for your help.  Your help is some of the best I have ever received on EE.

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