AP 350 Bridges with a Repeater....

[MICHAEL YOUNG]

Scenario: Have 3 Bridges....in the following diagram...

Bridge 1 -----------------Bridge 2-----------------------Bridge 3

Bridge 1 is seperated from bridge 2 by 2 miles. Bridge 2 is seperated from Bridge 3 by 2 miles. Bridge 1 is seperated from Bridge 3 by 4 miles.

Setup: Have One Yagi Ant. at Bridge 1 to One Yagi plugged into Bridge 2 (Right). Have Another Yagi Ant. at Bridge 2 (Left) pointing to Yagi at Bridge 3.

Configured: Bridge 1 is set to Root Bridge, Bridge 2 is set to Repeater and Bridge 3 is set to Non-Root without Client

Verified functionality and connectivity with no Wep, with WEP and with LEAPA configured.

Full end-to-end connectivity (Signal strengths are good and signal quality is good. Data rate is good also......)

Question: Why is Cisco saying this is an unsupported configuration. They recommend another bridge in the middle and a cross-over between the bridges....the diagram of there suggestions below....

Bridge 1 -----------------Bridge 2====Bridge4-----------------------Bridge 3

Root Non-root/client Root Non-root/client

I've been doing radio installs for a long time and after getting this to work correctly with the three bridges, why am I getting so much resistance to this configuration. (By the way I had problems with 11.10 and 11.21 code using LEAP in the scenario....the Repeater would change rolls after each Key rotation.....12 code fixed this issue)

I have talked to other RF experts and they don't see an issue either. They bring up the concept of placing a Omni directional Ant. at the Repeater.....would Cisco recommend this they ask....I have been told you need 2 Bridges for the repeater portion. This sounds very wrong. I now of other Wireless bridges that have a repeater portion that doesn't require 2 bridges to make a repeater.

I just need some answers, because I'm getting tired of fighting this battle...

Thanks

[michael_r_clark]

In general, this scenario (from a purely wireless point of view), I like "Bridge 2" to be the Root with an Omni, and the other bridges as clients. I can't understand why they wouldn't support that, unless there is an authentication issue. Doesn't make sense.

[MICHAEL YOUNG]

The only difference is Bridge 1 is connected to the network of choice and the other bridges are an extension on that network.....

I'm still at scratching my head on this also....I talked with an Amplidyne Wireless engineer and they say they have never had this issue (They only have one radio in there repeater also). I've have friends that implemented other solutions because cisco said they don't support this configuration. They say it is unsupported with TAC and that RF will "eventually have problems". This seems like a silly statement. You either have RF issues when you install it or not...(unless you have external RF noise levels, etc....)

I was told today again today that this configuration is wrong.....

I would like an answer.....we'll see.....

[derwin]

I am not sure who has told you that it is not supported but you might like to read this.

http://www.cisco.com/univercd/cc/td/doc/product/wireless/airo_350/350brdgs/brscg/br350ch8.htm#1016685

As you can see it is supported and even given as a sample config.

The caveat here is that the "repeater bridge" must be in bridge non root with clients mode.

If you configure the bridge in AP repeater mode then you ONLY can have client devices and not bridges associate to it.

The set up with 4 bridges is recommended as when you use a repeater you will half your throughput, as the repeater has to receive the packet then re transmit the packet. This can also add to congestion (every packet is transmitted twice) in the radio network, further adding to throughput problems as it is a shared media.

The 4 bridges can be on 2 different channels and 2 sets of ssid's making them seperate radio networks that *should not* interefer or congest each other.

The suggestion of making the middle bridge the radio root is also valid, as long as all RF planning aspects are taken into account. (root radio has no bearing on spanning tree root)

I would strongly recommend that you use the 4 bridge solution as the disadvantages of the 3 bridge setup outweigh the cost savings in my opion

[MICHAEL YOUNG]

Is there any way I could get written information on the 3 bridge setup.....? The Cisco SE here says that she's getting info from the business unit that the 3 radio configuration is not supported... (Mind you this is a configuration that has the middle bridge (repeater) with one yagi connecting to the right ant. port and another yagi connecting to the left ant. port each pointing to the other bridges.) I not sure why cisco would not support this. If it works fine (from my experience) why would the cisco wireless business unit not support this....

I need more docs.....

Thanks

[derwin]

Ok the problem is not the configuration of your bridges.

The problem is using 2 directional antenna pointing in different directions, that is NOT supported.

The reason for this is that the 2 antenna ports are for diversity only. The bridge will transmit out of the antenna selected in the config. For receive it will monitor both (as long as selected in the config) and take the best signal. At any point in time only one antenna is being used.

This is to minimise the effect of multipath loss.

You can not use them as 2 seperate antenna pointing in two different directions. Given what I have just described I highly doubt you could have a reliable radio link in both directions using this combination of antennas

[MICHAEL YOUNG]

I beg to differ.......We got wonderful data rates with very good signal strength....in both directions....

Symbol and Amplidyne say there radios work fine doing this....Is it a code issue with cisco....

[selphj]

Yes!! Thank you guys! We've had our BR350's in this exact configuration and they've been going down like crazy. Our "certified" cisco reseller told us you could put 2 directional antennas on a br350 and point them different directions without any problems. We've replaced every unit, we've tried every (literally) firmware version and nothing has made our setup stable. Sometimes it works for a few weeks, and then it would start going down again. Then I found this discussion! I've changed our BR350's so that we only use the primary antenna connector, and added a second BR350 in the required repeating spot. Everything, knock on wood, seems just fine now! Thank you for starting this thread!

[MICHAEL YOUNG]

I've had extensive talks with Cisco engineers about this issue....I have found that when a bridge receives a signal in one antenna it tries 30 times to send it out the one antenna before it sends out the other. They have told me that it's a code issue that can be solved by placing a T and setting both send and receive on that port. Other vendors don't have the issue you may be having, but after talking with several cisco wireless "GODS"....it seems that for the money it would be best to place another bridge in the equation. My whole reasoning for starting this thread was to get and receive ideas and help myself and other try to solve this problem. I don't think you should "dog" "certified cisco reseller in general, because we try to solve sol'n's for customers and try to do it with the best engineering in mind. If you were having problems like this, then sure add another bridge....but my whole point was the many people that weren't having problems with this setup. I was trying to get technical reasons from cisco explaining this so I could go back to the customer(bunch of wireless guru's) that wanted it this way and explain the problems without looking like an ass. The issue with the sending out one antenna port 30 times before sending out the other is a design issue. Cisco says that by the time it sends out the antenna port, the sending device may timeout and drop the packet. I try to keep everyone informed on this....

Thanks