Re: Failed to get DHCP response on interface "Marking interface
looks like you could be using interface group.
(WLC) >show interface group detailed
Interface marked with * indicates DHCP dirty interface.
whenever the existing interface goes dirty does the client tries the next available interface for dhcp.
The idea of Interface Groups is that you can have a WLAN utilize multiple interfaces/VLANs/Subnets/DHCP Pools, either for load balancing. At its heart it is purely round robin or based on hash generated using mac address(it depends on the wlc code), but should a client connect in on a certain interface and not be able to complete the DHCP process we mark it as dirty for 30 minutes. During those 30 minutes we basically remove that Interface from the Interface Group as it won't be selected for use.