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Apparently Impossible Config due to 802.11 Limitations?

Posted: Thu Mar 05, 2009 5:28 pm
by earljack
I have a RB133 that I want to use to repeat a signal off my tower for 2 customers. My tower does not support WDS (yes I know they are ancient, and I am planning on upgrading them to RB433AH's later this year), so any kind of workarounds that use WDS to link to my tower aren't going to work. What I want to do is repeat the signal off my tower without using any new subnets or setting up any new RIP neighbors or anything like that. This is just for 2 customers and I feel that doing such things would be unnecessary.

My first thought to accomplish this was to have wlan1 (the client) connect to my tower (gateway of 10.0.41.1/24) and set its IP to 10.0.41.2. Then bridge it to wlan2 (the repeater) which would be set in AP mode. In my mind since wlan1 and wlan2 are bridged together it should pass the traffic through wlan2, to wlan1, to the tower, and off through my network. However, this does not work. I tried setting the IP (10.0.41.1) on wlan1, wlan2, and on bridge1 (the bridge that includes wlan1 and wlan2) but it still does not work.

After a little searching through the forums I did not find much solid evidence that proved what I wanted to do was possible or even impossible. However, I did find this interesting comment stating “Wireless interfaces that operate in station mode can not support transparent bridging” in this thread http://forum.mikrotik.com/viewtopic.php ... n+repeater

So, since it seems bridging won't work, is there any other way to accomplish what I want to do without upgrading my tower to support WDS or changing the RIP configuration on my tower to talk to my RB133?

I have accomplished this same thing a few times with two CPEs and a crossover cable. For example, in this situation I would put the first CPE on 10.0.41.2 and the second one on 10.0.41.3 and connect to the second one and set my gateway as 10.0.41.1, and everything would route properly.

Also, I had thought of getting rid of the bridge on the RB133 and just set wlan1 as 10.0.41.2 and wlan2 on 10.0.41.3, but I think I am missing something with the routing. Sorry if the answer is obvious. I am relatively new to ROS and I only have a few RouterBoards on my network, but I plan on replacing most of my network with RBs over the next year or 2.

Thanks for any advice guys!

Re: Apparently Impossible Config due to 802.11 Limitations?

Posted: Fri Mar 06, 2009 5:35 pm
by Aug
You can either set wlan1 to "station psuedobridge" and wlan2 to "apbridge", then bridge the two interfaces. Clients will need to be on the same subnet as backhaul.
/interface wireless
set0 mode=station-pseudobridge
/interface wireless
set1 mode=ap-bridge
/interface bridge
add name=bridge1
/interface bridge port
add bridge=bridge1 interface=wlan1
add bridge=bridge1 interface=wlan2

OR
(recommended)

You can set wlan1 to "station", connecting to your backhaul with IP in the same subnet as the backhaul. Then set wlan2 to apbridge with a differnet ip subnet. Then nat wlan2 to wlan1.

/ip firewall nat
add action=masquerade chain=srcnat comment="" disabled=no out-interface=wlan1

Re: Apparently Impossible Config due to 802.11 Limitations?

Posted: Fri Mar 13, 2009 5:48 pm
by earljack
Your suggestion worked like a charm. I used "station psuedobridge". It was not available on the stock 2.9 firmware, but I got it upgraded to 3.20 and found it.

Is "station psuedobridge" some proprietary MikroTik solution to overcome the 802.11 limitation of station bridging? Or is this something I can expect to find on other high end routers? I.E. is "station psuedobridge" an addition or official amendment to the 802.11 spec?

Thanks again for the helpful advice!

Re: Apparently Impossible Config due to 802.11 Limitations?

Posted: Fri Mar 13, 2009 7:20 pm
by rmichael
Your suggestion worked like a charm. I used "station psuedobridge". It was not available on the stock 2.9 firmware, but I got it upgraded to 3.20 and found it.

Is "station psuedobridge" some proprietary MikroTik solution to overcome the 802.11 limitation of station bridging? Or is this something I can expect to find on other high end routers? I.E. is "station psuedobridge" an addition or official amendment to the 802.11 spec?

Thanks again for the helpful advice!
It's nonstandard (but can be done using other routers as well). Pseudobridge explanation:
http://forum.mikrotik.com/viewtopic.php ... ge#p116214

Re: Apparently Impossible Config due to 802.11 Limitations?

Posted: Sat Mar 14, 2009 3:24 pm
by popcorrin
I have accomplished this same thing a few times with two CPEs and a crossover cable. For example, in this situation I would put the first CPE on 10.0.41.2 and the second one on 10.0.41.3 and connect to the second one and set my gateway as 10.0.41.1, and everything would route properly.
I did pretty much the same thing with two deliberant cpe's but I have one set in client bridge mode and the other set up in ap bridge mode and it works just fine. No wds or anything.

I didn't think it would work because I read the same statement “Wireless interfaces that operate in station mode can not support transparent bridging” but I haven't had any problems.