Wireless Access

Occasional Contributor II

Strange connectivity issue, appears DHCP related

I have just taken over several networks as part of my job.  All of them are using Aruba AP-105 access points in Virtual Controller mode.  There are two wireless networks on each.  Wireless clients are being handed their addresses by a Windows Server performing DHCP duties.


In one building, I am getting reports (which I confirmed) that at certain times of the day, users in specific areas of the building are having extreme difficulty connecting.  If they move to another area of the building, they are able to connect.  While in the building this morning, I checked, and was able to see that it appears that the systems show excellent signal strength to the access points, and are even showing connected in those areas, but are not receiving their network address from the server (and thus are showing connected, but with a 169.x.x.x address).


This happens mainly in the morning; as the day goes by, things work better in the afternoon.  As we are in education, I could easily see that the morning is when our students arrive and the issue begins.  I have made changes to my predecessor's configuration of the network (adding static IPs to the access points, and updating to the latest firmware), but this so far has not resolved the issue.


Does anyone have any suggestions?  Are there logs I can pull from the system to monitor what is happening when users are trying to connect?


P.S.  Other possible notes that might be useful:

We have two wireless profiles(networks) in our setup, one for staff, and one for students.  Each would be considered as having a different VLAN and DHCP scope.  I can't confirm that my predecessor set this up properly, so even the most basic suggestions are helpful.

Re: Strange connectivity issue, appears DHCP related

Do you have drop multicast /broadcast enabled ?

Make sure that your dhcp leases are not running out ( go over the dhcp logs) maybe you have exceeded the amount of IP addresses

Make sure that there's no port errors going to the IAPs or going up to where your dhcp server is

Is this happening with certain type of clients ? If it is make sure the drivers are up to date

Chech the logs in the IAP to see if there's any indication that the IAPs might be bootstrapping

Have you guys made any changes recently ?
Thank you

Victor Fabian
Lead Mobility Architect @WEI
Occasional Contributor II

Re: Strange connectivity issue, appears DHCP related

We have a broad subnet, and plenty of addresses --this was the first thing I checked.

Lease time is currently one day.

The issue is happening with multiple clients; we have experienced it with systems that have Broadcom and Ralink wireless chipsets.

Broadcast filtering is disabled.


I am inheriting this issue as part of a new position, and I have been told it has been going on for some time.


Alerts in Instant are showing a lot of DHCP timeouts as well as some "Wrong Client VLAN" errors.

Occasional Contributor II

Re: Strange connectivity issue, appears DHCP related

I believe I have found the culprit.  It looks like a number of switchports were not tagged for the proper VLANS.


Because several access points *were* connected to properly configured switchports, users would sometimes get an IP address if they were in range.  Otherwise, their systems would connect and get nothing at all, due to having no IP address.

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