Upgrading a bridge/AP

Unanswered Question
Dec 30th, 2007

I currently use a WGB352B configured to attach to an AP1231G for a remote buildings connectivity. The buildings are about 1200-1500 feet apart. I have Yagi antenna's on each side. Signal quality typically ranges 70-80%, but strength is between 30-55%. I would like to improve both strength and speed between these connections, but don't know the current Cisco line well enough. Advice?


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bcolvin Sun, 12/30/2007 - 16:34


the best solution with out replacing the existing 1231 would be to replace the WGB with a second 1231 running in WGB mode this would allow to increase the speed to "G" data rates for the bridge. checking the alignment of the yagis and the condition of the conectors especialy if the outdoor ones arn't weather proofed.

Signal quality is more important than strength but refer to the tables that reference the signal strength in db rather rthan percent. this will give you a more realistic expectation of wht your data rate can be with good signal qualuty.


Reference the above link for data rates rates vs signal strength


The above link is to a bridge calculation tool

The Cisco Outdoor Bridge Range Calculation Utility is the best tool to calculate the Fresnel zone, the distance between bridges, cable loss, required antenna height and the recommended fade margin. Cisco strongly advises you to use this utility as a part of the site survey to calculate the range parameters, before you deploy the bridges. This ensures higher throughput and consistent bridge performance.

Good luck


tgr33n Thu, 01/03/2008 - 16:11


Thanks. The 1231 would improve the speed, but the performance is worrying me more. The strength in is about -76dBm. I find the bridge tool next to useless. To start the products I have are not in the tool. I'm measuring things in feet, not miles. My Yagi's are about 30' off the ground with good line-of-sight. There is a tree that may impact the Fresnel, but it's on the fringe at best, for now ;-) When it grows more it could be bigger problem. Is there an updated tool that includes current products?



bcolvin Thu, 01/03/2008 - 21:29


I agree about the tool but it will give some of the information you need Cisco has not updated the tool for newer products. But for the RF path calulations the frequency, antenna gain and power determins the fresnel zone and signal strength regardless of the actual product. For another free tool use the following link. again it is in miles but will accept decimal fractions.


I use the calulator supplied with AirMagnet Surveyor the attached jpeg shows an radius of 12.74ft for 3/10ths of a mile so it look like you are okay on that.

also with a link that is at -76db you will probably be able to run "G" Data rates with out any problem just watch the retries to determine your max re;liable datea rate.


tgr33n Sat, 02/09/2008 - 05:53


I have finally acquired a couple of 1231's. Both appear to be working normally. I have one in AP mode, and the second in WGB mode. The AP is working great. The WGB however "bounces" when connected. There are four messages that repeat within every 10 seconds.

1) Interface Dot11Radio0, parent lost: Received deauthenticate (2) not valid.

2) Interface Dot11Radio0, changed state to down

3) Inter..., Associated to AP Farley_AP1231G, MAC [None]

4) Inter..., changed state to up

Connectivity is unreliable at this point. I believe I have configured the WGB correctly, but obviously not :-) When I replace the 1231 with the 351, all is well again. Any ideas?

Thanks much


bcolvin Sat, 02/09/2008 - 21:26


I know that WGB was not all that stable in the earlier releases of IOS 12.2 and early 12.3. Suggestion update to a current release of the IOS to see if that cures the problem or If you don't need the WGB to be mobile/able to roam. one of the features of the WGB over normal bridges, will configuring the Root AP as Root with clients and the current WGB as non root with or without clients work for you. but as always as you have probably seen in these dialogs newer software is usually better.

I agree with you though those old 350 bridges do work.

Fight the good fight


tgr33n Sun, 02/10/2008 - 11:49

Bill, When I acquired the 1231's, I knew I would need to update the IOS. I was right. All three are running on 12.3(8)JA2, which looks like the most current on Cisco's website. Can you confirm?

Not sure about your other suggestion. The AP is configured on the bulk/primary side of our network. It connects to the WGB-AP which has a small network (single switch) with the third AP providing 100% wireless coverage of this small network. I understood that a Bridge cannot be an AP at the same time. Please clarify.




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