wireless dhcp issue after upgrading WLC to 7.6.100

Unanswered Question
May 16th, 2014
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Hi All,

We have upgraded our controllers to version 7.6.100. After upgrading, the access points also upgraded their version to 15.2(4)JB3. But, the problem is that after this process the APs do not get IP. It stays on this state:

*Sep 26 03:55:36.334: %CAPWAP-3-DHCP_RENEW: Could not discover WLC using DHCP IP. Renewing DHCP IP.

Not in Bound state.

The DCHP configuration is OK, since it is working in other two controllers we have and that we are not upgrading untill this issue is solved.

If we connect the APs via console and configure a static IP and controller's IP, the AP registers and works fine. But, the access points are located in 20 remote sites, so we would like to avoid going site by site.

Has anyone suffered this issue and knows how to "recover" those access points?

Thank you very mucho for your help!

 

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Josu Bagazgoitia Wed, 06/18/2014 - 23:39
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Hi,

Thank you for your answer conraddaniel.

But, our issue was an error on the DHCP. The DHCP server pool for the APs was configured with lease time infinite (on a Cisco 6500). After capturing the packets and debugging on the AP we realized that the AP were receiving wrong values:

  • DHCP: Scan: Renewal time: 2147483647
  • DHCP: Scan: Rebind time: 536870911

So, on the AP debugging we saw:

DHCP: Scan: Renewal time larger than Rebind time

On Cisco documentation:

T1 Timer(Renewal) After a certain portion of the lease time has expired, you attempt to contact the server that initially granted the lease in order to renew the lease so its IP address can still be used.

T2 Timer(Rebinding) If renewal with the original leasing server fails, because, for example, the server was taken offline, then you ideally try to rebind to any active DHCP server and try to extend its current lease with any server that allows it to do so.

These T1 and T2 timers can be any values, but must be less than the IP address lease duration. T1 Timer must be less than T2. Generally T1 is set to 50 percent of the lease duration and T2 is set to 87.5 percent of the lease duration. Use this rule to set T1 and T2 timers.

On the previous version of the WLC, the DHCP was configured in the same way and we confirmed that the APs received same times, but they ignored those wrong values.

The workaround was to modify the lease time of the DHCP pool (1 day). This way, both timers had valid values and the APs accepted the DHCP OFFER. We still do not know why with lease infinite these timers have wrong values (a bug?).

 

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