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New Member

All AP350 clients regularly dropped w "Sender is Leaving (has left) BSS"

Each of my 80 Aironet 350 AP's (all with 12.02T1 firmware) drops all its clients about one to ten times a day with this log message for each client:

Disassociating [al]00022d1b5416, reason "Sender is Leaving (has left) BSS"

Within a few seconds that's followed (for each client) by:

Station [al]00022d1b5416 roamed

Disassociating [al]00022d1b5416, reason "Not Associated"

Station [al]00022d1b5416 Authenticated

Station [al]00022d1b5416 Associated

Since the break in connectivity is short, most web browsing is not visibly affected, but telnet, ssh, messenger, and other sessions are terminated.

In all the cases I'm aware of, the clients were stationary at the time they were dropped, so this doesn't seem to be a result of physical roaming. My own machine, for instance, gets dropped even though it is sitting on my desk almost all day, 20 feet and one or two sheetrock walls away from the AP, with SNR about 50dB.

I thought this might be due to external radio interference, but I've got all the AP's logging to a syslog device and I see no sign that AP's close to one another tend to drop clients at the same (or nearly the same) time. The once-a-second "site monitor" client log of my own machine shows no sign of increased noise near the times it gets dropped. There are no CRC errors in the AP logs.

I thought it might be some kind of client problem, but our network uses a number of clients and all are affected. Most of our several hundred clients are Dell Truemobile or Orinoco gold, but about 15% are Macs and we have a smattering of Aironet, Linksys, Netgear, etc. The logs show no obvious sign that the drops are related to the type of client connected.

Could the AP's be interfering in some way with one anther? We do have a lot of AP's with overlapping ranges, but we've tried to minimize the interference by using fixed radio channels 1, 6, and 11 and having the closest AP's use different channels. There are still many places where AP's on the same channel have some overlap, though. My own computer is in an area where it sees no other AP's on the same channel as the closest one, and I still get dropped by it several times a day.

The logs show that some AP's are much more likely than others to drop their clients, but I'm not sure why. In the past two weeks, for instance, my own local AP has dropped its clients (it generally has four or five) about 100 times, while the next-most-pesky AP in this contest has dropped its clients only about half as often.

I thought this might be some kind of trouble with load balancing, so I turned off Aironet extensions on all the AP's, but there was no change.

Someone suggested that it would help to set the AP to take "no action" if it looses wired network connectivity, but I saw no change after I reset all our AP's to do that.

So I'm at a loss how to solve this vey troublesome problem, and I'd very much appreciate any advice.


Re: All AP350 clients regularly dropped w "Sender is Leaving (ha

Try setting the transmit power to a lower rate on the AP's instead of the default 100Mw. This will help if there is an overlapping problem.

New Member

Re: All AP350 clients regularly dropped w "Sender is Leaving (ha

We also are experiencing this problem, after upgrading approx 100 units to now ver 12.02. We cannot seem to resolve this issue and have tried changing every setting which might affect this problem. We have noted that this problem is isolated to the 340 series as we also have a number of these in service.

We would really appreciate some help as well, and would like to get this problem corrected ASAP.


New Member

Re: All AP350 clients regularly dropped w "Sender is Leaving (ha

We have all 350's. We seem to have solved this problem by downgrading to 11.23T and/or disabling VLAN support in 12.02T. Here's what we've done:

1) Downgraded five AP's (of 150) to 11.23T. None of the five have had dropouts in many days, though there had been several a day on each of them up to then, and dropouts continue on many other AP's on our network.

2) After downgrading the worst AP dropout offender, and seeing that it stopped dropping for several days, we restored it to 12.02T in the expectation that the problem would reappear. It didn't. But we hadn't enabled VLAN support, either. We need to see what happens when we restore VLAN support, but we haven't done that yet.

3) At the same time, our semester ended and almost all our students' wireless laptops disappeared. Dropouts continue at a reduced level in classroom and office buildings, but we haven't pursued the problem very aggressively.

4) At the same time that we down-graded the AP firmware on those five AP's and saw the dropouts disappear, Mac's began crashing--some several times a day. They didn't crash when put on the wired network. Downgrading the local AP seemed to solve Mac crashing, too, though the crashing is rarer than dropouts, so harder to be sure about, especially as the network traffic drops at the end of semester. Plus, I'm just suspicious of blaming every problem on one scapegoat.

But we are convinced that downgrading solves our problem as it seemed to solve Kevins, but we have loose ends to investigate, and we haven't downgraded the whole network yet..

We upgraded to 12.01T and 12.02T and we enabled VLAN support because we have an important use for it. So we really hope a solution can be found that includes VLAN support.

New Member

Re: All AP350 clients regularly dropped w "Sender is Leaving (ha

We have downgrade the AP's firmware to 11.23T. on two 350's that have this problem. This seems to have corrected the problem on one AP but has not on the second. Here is the problem:

The access point does not reply an icmp request from our monitoring software for approx 2 to 7 minutes. (This occurs frequently) During this time, the associated clients still have signal but are unable to transfer packets and either dissassociate/reassociate/dissassociate themselves or remain until the AP begins to transfer data again.

We have the eithernet side hard coded to 10 baset with a catalyst 2900 xl.

The AP ethernet is also set to "no action". The radio side HW (hardware) rates are set to basic, yes, yes, yes, with the fragment size set to 1024, with a power of 100mw. Wep 40 bit is enabled.

Aironet extensions are on as all client devices are Cisco. These include both PCI and WGB. The WGB are not considered part of the infrastructure on the advanced radio page. On average we have 20 to 30 users per access point.

This problem seems to only affect the 350 series. Downgrading the firmware is not a desired option for as we utilize multiple SSID's for both roaming and fixed clients.


New Member

Re: All AP350 clients regularly dropped w "Sender is Leaving (ha

Hi Kevin,

No solution but I have experienced the same problems. We have 49 remote 350's connected to Cat2950's. We have been experiencing intermittent dropouts of access points with certain units seeming more prone than others. We have been finding a hard reset is the only solution to get them back on-line asap. We use 12.03T release. Also we too have been finding our monitoring which is ICMP is not responding, however ours does not return until you manually reset the unit. And finally we have several MAC users who have been experiencing the same issues you mentioned regarding dropped connectivity.

I would be keen to find out if you find any solution other to downgrading the AP firmware.