Trunk connected access points dropping traffic test shows trb with VTP

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Aug 27th, 2008
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The all the wireless access points at this building are dropping traffic during the overnight. In looking at our monitoring tools we can see that all of the APs CPU level spikes to 90-100% during the timeframe that traffic is being dropped. Both the hard wire LAN interface and the RF interfaces utilization is very low, no reason for traffic to be dropped, IE appearance that the traffic is being dropped because the AP is too busy internally.


The APs are connected via a dot1.q trunk to cisco 2948 switches. There are only 2 vlans on the APs, so on one switch port that one AP was connected to we added the config to block all vlans except for these two:


clear trunk 2/48 2-249,251-999,1025-4094

set trunk 2/48 on dot1q 1,250,1000-1005


Afterwards this specific AP did NOT have its CPU spike and it did not drop traffic. We do not have this issue in any other building and thus suspect there is a bigger problem with trunking/VTP domain.


Attached is a word doc with screenshots showing the problem, one of the access points and the switch that the access point is connected to.


Thanks for your help!! ~ Phil



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vmoopeung Tue, 09/02/2008 - 06:27
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You may try upgrading the AP to the version (12.3(7)JA3)


Also, You may also try configuring the command “switchport trunk allowed vlan 1,4,42,142 “ (for eg) on the ports where the access points are connected and allow only the VLANs that are relevant to the wireless network.

This command is necessary if you are connecting an access point on to that port to avoid high cpu utilization and if

the allowed VLANs are not specified for that access point, unnecessary traffic is going to be transmitted to the access point and it will be processing and dropping that traffic.


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