Mesh AP heart beat time out

Unanswered Question
Aug 6th, 2009

Hi there,

I am running a network of 10 1522 Mesh APs and the APs keep on disconnecting from the WLC with the following traps:

50 Thu Aug 6 19:28:24 2009 AP Disassociated. Base Radio MAC:00:24:c4:ab:64:f0

51 Thu Aug 6 19:28:24 2009 AP's Interface:1(802.11a) Operation State Down: Base Radio MAC:00:24:c4:ab:64:f0 Cause=Heartbeat Timeout

52 Thu Aug 6 19:28:24 2009 AP's Interface:0(802.11b) Operation State Down: Base Radio MAC:00:24:c4:ab:64:f0 Cause=Heartbeat Timeout

what could be the possible reason for the 'Heartbeat Timeout'?


I have this problem too.
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jeromehenry_2 Thu, 08/06/2009 - 06:53


All RAPs and MAPs (through the RAP) send a keepalive message to the controller, typically every 30 seconds.

If this process fails, you get this message.

The reason why this fails is basically because your MAP cannot get in touch with your controller in due time. This is the easy answer.

Now why is that? This is harder to determine. There is something that prevents your MAP from communicating in good conditions with the controller. This communication occurs through the backhaul, so logically on the 802.11a spectrum, but when the AP fails to reach the controller, the WLC sees the whole AP (therefore both radios) going down.

I would:

- verify that this message is only about the MAPs, thus limiting the issue on backhaul communication problems. If the issue shows also on the RAP, you have a bandwidth issue on your LAN as well.

- Check the backhaul parameters, through the controller or WCS. It may be that you have bandwidth issue at the RAP level (check the RAP utilization on 802.11a). It could also be that your default data rate on the backhaul is too high (check packet loss rate on your MAP 802.11a, and reduce the backhaul speed accordingly). Could also be that you have interference issues...

wg wireless Thu, 08/06/2009 - 07:43

Thanks. It was really helpful. I think the issue with my network is LAN bandwidth. I have to check it out though coz there are no problem of 5 GHz interference in the area and backhaul SNRs of Mesh APs are also quite reasonable.

What should be the data rate setting on backhaul links. currently its set to 24 Mbps?

wg wireless Thu, 08/06/2009 - 07:47

Thanks it was really helpful information.

I think the problem in my network is LAN bandwidth. I have checked for congestion at 5 GHz and backhual links SNRs and there is no issue with that.

What should be setting on backhaul data rate? currently its set to 24 Mbps

jeromehenry_2 Fri, 08/07/2009 - 17:49

I couldn't really tell what "should" be the data rate on the backhaul, as this depends on the distance between your APs and the RF conditions...

Default speed is indeed 24 Mbps, and this is ok if your SNR between APs is above 20 dBm and if the packet loss rate on the link is less than something like 6 to 8%...



dlawson001 Wed, 09/30/2009 - 08:30

Heartbeat is probably the Hello times. If you are getting a timeout then your radios aren't reaching the other access points and hence losing connections with the other controllers.


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