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3500 AP and 1042 don't get DHCP IP address when joining a WLC 7.3 or 7.4

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Introduction

In this document Cisco TAC engineer "Siddharth Vij" has explained about the issue seen on 3500 AP Hardware Revision 2 and 1042 AP's Hardware revision 4, connecting to a Layer 3 VLAN switch port only with a broadcast IP address set on the VLAN Interface something other than 255.255.255.255.

 

If these AP's are connected to a Layer 2 VLAN or the same VLAN as the management interface or the controller, they have no issues in getting an IP address from the DHCP server and joining a WLC running 7.3 or 7.4 codes.

 

These APs when trying to join a WLC running 7.3 and 7.4 code don't get an IP address assigned to them from the DHCP server, assigning a static IP address manually makes the AP to join the WLC running 7.3 or 7.4 software versions.

 

This issue is not seen on WLC running 7.2 and below software versions.

 

Problem

The Access Point AIR-LAP1042-A-K9 is not getting IP from the DHCP server with software versions 7.3.112.0 and 7.4.100.0 on the AIR-CT5508-K9 controller. If the controller is in version 7.0.240.0 the AP receives IP by DHCP.

 

In versions above 7.0 only when configuring static IP (lwapp ap ip address IP MASK) the AP joins the controller. Both AP and controller are in the same VLAN and there is a DHCP server on that network.

 

Here is a sample of the log in the AP console:

 

***
*Apr  5 14:39:49.368:  CAPWAP-3-ERRORLOG  Not sending discovery request AP does not have an Ip !!
*Apr  5 14:39:49.372:  CAPWAP-3-DHCP_RENEW  Could not discover WLC using DHCP IP. Renewing DHCP IP.
*Apr  5 14:39:59.373:  CAPWAP-3-ERRORLOG  Not sending discovery request AP does not have an Ip !!
*Apr  5 14:40:09.372:  CAPWAP-3-ERRORLOG  Not sending discovery request AP does not have an Ip !!
*Apr  5 14:40:19.372:  CAPWAP-3-ERRORLOG  Not sending discovery request AP does not have an Ip !!

*Apr  5 14:40:29.372:  CAPWAP-3-ERRORLOG  Not sending discovery request AP does not have an Ip !!
Not in Bound state.
***

 

How to make the AP's receive IP from the DHCP server on versions above 7.0?

 

Solution

This issue happens due to the layer 3 VLAN SVI on the switch having a "ip broadcast-address <ip-address>" configured with something other than the default broadcast address "255.255.255.255".

 

Removing the broadcast address command or making the broadcast ip to default 255.255.255.0 resolves this issue.

 

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