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I am new to this forum and would like to have your advice in this problem.

My warehouse uses wifi handhelds and wifi printers with Cisco AP. Sometimes ( may be 1 day, maybe a week ) one or more printers are acting up. They do not print, and when I ping those printers, it takes a very long time for the echos, maybe to 15 or 20 seconds while it takes only around 300 ms when they work normally.

When that problem happens, all the handhelds and other wifi notebooks work nornally, and the ping/echo time is just normal for these devices.

And the way to fix it is pretty strange : Changing some parameters on the AP ( like max retries ) to any number ( plus one or minus one ) will fix the problem immediately. Then some days later, it happens again, this time I change those same parameters to the previous parameters to fix it.

I do not think those parameters have anythging to do with this problem, but it is the 802.11B controller on the AP resets some other things that make the printers work again.

Any advice is really appreciated.


Vu

Max Retries could have an effect on connectivity problems. A low Max Retries value may cause a loss of connection for stations with a shaky RF signal. A high Max Retries value could bog down the network with stations retransmitting when they have a shaky RF signal. The bottom line is, it's possible that Max Retries could be solving your problem.

Given that you are arbitrarily moving Max Retries back and forth, it seems unlikely that this is, in fact, a real long term solution to your problem. As with any out of the ordinary Wi-Fi connectivity problem, the best idea is to sweep the area with a spectrum analyzer to make sure there isn't significant interference, then do several packet captures to see exactly what is happening when you try to connect.

Cheers,
Ben

Hi Ben,

Thanks for the explanation of Max Retries.

Two things I would like to do :
1. As your suggestion to capture the packets when the problem happens. I would like to have some tool that can help me to do this remotely because normally I stay in my office, and when I get to the warehouse ( about 30-45 minutes driving ) then the problem may not exist any more. Any suggestion for such tool ?

2. This weekend I am going to upgrade the IOS of the AP.

Thanks again,

Vu

Just a follow up.

I upgraded the APs to the newer IOS (12.3(7)JA) two weeks ago, and so far I have not got any call about this problem.


Vu