Max-retries reached

Unanswered Question
Jun 20th, 2008

Hi All,

One of our clients has got a 1200 cisco AP which is their only way of connection the network (no RJ45 cabling is present in their office). They are complaining about the slowness of their network, so first I thought that it is simply a problem with too many users connecting to the same AP, but when checking the interface outputs, I found that the tx/rx=1/255. At the same time I found that there are plenty of output errors on the Dot11Radio0 interface. There are also a few interface resets. Then I checked the logs and I found that there are plenty of maxretries reached messages.

I read a few forums and they say that this might have something to do with interference. Then I ran a carrier-busy test and that showed a number under 20 for all channels, so I belive it is not the problem.

I attached a file with the outputs in case you would like to see what I am talking about.

Thanks for any comments in advance and please let me know if you need any more information.



I have this problem too.
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Scott Fella Fri, 06/20/2008 - 05:41

The carrier busy test will not show you accurate information regarding interference. It seem like this is a small office with only one ap. Is the ap near a microwave oven by chance?

attish120 Fri, 06/20/2008 - 07:50

Hi fella5!

Thanks for your quick reply!

Do you think by the output that the problem is caused by some interference? Also, do you know of any accurate way to measure interference?

There is a microwave oven in the office, but there are 2 walls and about 6 metres bw the AP and MW oven.


jeromehenry_2 Fri, 06/20/2008 - 08:13

Sharp analysis Fella5 (and 4 for you)! Could be interferences near the AP or near the client (which could be closer to the microwave oven).

Cisco has a great tool for measuring and analyzing non 802.11 interferences, it is Called Cisco Spectrum Expert (formerly Cognio). It will tell you if there are interferences, probably what they are, and will help you locate them.



Scott Fella Fri, 06/20/2008 - 12:23

Jerome is right.... Cognio is a great but expensive tool. Wi-Spy might be a good cheap tool just to help you get by. It only works for the 2.4Ghzs pectrum.

attish120 Sun, 06/22/2008 - 23:54

Hi Jerome/fella5,

Thanks for your help.

Today I went on site and I found that the AP was lying on top of the server, so I moved it further away from it. I believe that this is going to resolve the problem, but I cannot say anything until I monitored the network for a day or so.

Do you think that the server can cause some interference, or am I following a red herring? If this did not work, I will seriously think about getting my hands on a proper tool to measeure interference.

jeromehenry_2 Mon, 06/23/2008 - 00:12

Hey Attish120,

If "server" is one of those metallic boxes (:-)), then yes, it might be a good source of interference!

The AP antennas should be vertical and at least 1 meter away from any metallic source of interference, so a server could be a good candidate... but again, interferences can come from the AP area or the clients area...


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