wireless bridging with 1242AP

Unanswered Question
Mar 16th, 2010

I've got two cisco 1242 access points both with the same IOS, one is configured as a workgroup bridge and it connects to the other 1242 which is configured as an access point. I'm getting poor data speed between the two. I remember reading somewhere that bridging is done at reduced power on the 1242, is this why the data speed is poor? I get about 2mb/sec between the two. I know antennas and distance come into it but I've tried several different combinations but the most I get is about 2mb/sec. Are there any know settings that increase performance with bridging?

My second question is: is there any difference in performance with these ap's when used with an air-pwrinj or a normal DC adaptor?

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Scott Fella Tue, 03/16/2010 - 17:45

Should have no issues.... how far apart are the AP's and are you using 2.4ghz or 5ghz to link them up.  Maybe post your

show run so we can take a look.

tonyspcrepairs Wed, 03/17/2010 - 04:18

thanks for your response. I'm using the 2.4g terminals to connect. I don't have any problem connecting, it's just the data speed between the two is poor. Distance between the two ap's is about 10 yards through a glass window. I'm using the link to connect a server to a network. If I connect the server with a cable I get about 12Mb/sec transfer rate, but only about 2Mb/sec with wireless bridge.

attached is the configs of both devices.

Scott Fella Wed, 03/17/2010 - 07:32

If you are in the room that the server is in and you associate to the other AP, what connection speed and or throughput do you get.

tonyspcrepairs Wed, 03/17/2010 - 08:24

thanks for your response Tim that's an interesting command, valuable for the future. I ran it and attached is the result. Unfortunately Signal Strength: -53dBm and Signal to Noise: 41dBm means little to me I don't know if these are good figures or bad figures...

What is a good signal supposed to look like?

Scott Fella Wed, 03/17/2010 - 08:31

Tony, those are good readings so your connection from AP to WGB is fine.  Can you connect your laptop to the WGB and run test from that to see if you if are getting the same throughput.

tonyspcrepairs Wed, 03/17/2010 - 10:44

thanks for that info scott. I brought the wb into the same room as the ap and did some testing. Over ethernet cable I downloaded a file from another computer and I got about 12Mb/sec. Then, with the ap and wb only 4 feet apart I used the wireless connection and did the same thing, using the same file from the same computer, but I only got 3Mb/sec.

I did the test twice, first 2 using patch cables and an air-pwrinj, and then again using a DC power supply and a crossover cable, both times I got 3Mb/sec and both times the cli gave me Signal Strength: -23dBm and Signal to Noise: 70dBm.

So it would seem something is wrong. I should be getting more than 3Mb/sec with 2 x 1242's connected only 4feet away from each other.

Scott Fella Wed, 03/17/2010 - 10:53

Okay.. so verify that the PC and the WGB is negotiating correctly and that the speed nor the duplex is changing by looking at the log or doing a show interface bvi1 and also verifying you see no errors.  YOu can also set your data rate on the WGB to mandatory 48mb and 54mb and see if that helps, but at that close of a range, you should be connecting at 54mbps anyways.

tonyspcrepairs Wed, 03/17/2010 - 15:59

I did the checks as you say but no errors were present, all ports - router and wgb and ap - were all full duplex 100mbs, bvi ports on wb and ap showed no errors. MTU on all ports was 1500. One thing I did see was a setting for best throughput so I dotted that in both devices and the speed increased to 3.5Mb/sec. As a further test I got a wireless pc and connected it to the ap and did a file transfer exactly as before but I only got 2.5Mb/sec from the pc, which normally gives 12Mbs through an ethernet cable, this made me suspect the ap. The pc has a v strong wireless card connected to a big antenna so the signal was excellent. So then I got the wb, reconfigured it as an ap and did the same thing through that and got exactly the same results, so both devices perform the same. I also tried connecting a pc straight to the wb (not through the router) but it made no difference. I think I've tried nearly variation I can but I'm getting the impression this is the best I'm can get out of these 1242's, unless there's a magical setting I've missed...

Scott Fella Wed, 03/17/2010 - 16:18

Well if you calculate it... that seems about right...

100mb connection / 12mb throughput = 8.3333

54mb connection speed / 2 = 27mb actual wireless throughput without the overhead

27mb / 3.4mb actual throughput = 8.3333

Scott Fella Mon, 03/22/2010 - 18:39

When you tested throughput on the wire.... well if your ethernet (1242) is 100mbps and when you tested, you were seeing only 12mbps.  Take the results (12mbps and divide that by your total possible throughput (100mbps).  That is where I got that number.

Scott Fella Thu, 03/18/2010 - 11:49

Good point..... The 1242 ethernet port however is auto-sensing so it does allow you to use either.


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