WLC 9800 internal DHCP server and local switching

[Daniel Alejandro Castro Henriquez]

Hello everyone, I have a question. I need to use the internal DHCP server on my WLC 9800-40, but the WLANs are configured in FlexConnect local switching. For some reason, the clients are not obtaining IP addresses via DHCP. What could be the root cause? Is the internal DHCP server supported when using WLANs in local switching mode?

Best Regards.

[MHM Cisco World]

There is option dhcp central 

You need to enable it to make wlc run as local dhcp for flex AP clients

MHM

[MHM Cisco World]

MHM 

[Mark Elsen]

  - @Daniel Alejandro Castro Henriquez   That's a wrong architecture , make sure that the clients can use a local dhcp server too ,
                                                                Ref :  https://www.cisco.com/c/en/us/td/docs/wireless/controller/9800/technical-reference/c9800-best-practices.html#LocalSwitching
                                                                >...The local switching attribute and the VLAN that clients would use is defined at the Policy profile, as this is a policy associated to the WLAN. For a locally switched WLAN, just disable central switching and central association on the Policy profile. If the DHCP server is available at the local site, also disable central DHCP:
                                                                

  M.

[Daniel Alejandro Castro Henriquez]

Hi Mark,

Currently, the network is operating in local switching mode, and the client does not have a dedicated DHCP server. Therefore, the idea of using the internal DHCP server of the WLC 9800 was proposed. However, I have a concern: if DHCP Relay is configured on the SVIs of the remote sites, will the DHCP request reach the WLC, and will the WLC forward it through the network or via the CAPWAP tunnel? Do you have specific information on whether this is supported, or if the internal DHCP server is intended exclusively for Central Switching topologies?

[Mark Elsen]

  - @Daniel Alejandro Castro Henriquez    The client is disabling the benefits of local switching ; the idea is that the wireless infrastructure can keep functioning if the controller is not available. Hence the strong and as good as needed requirement to have a local DHCP server too.
  I don't have an exact answer to your questions also because they are going in the wrong direction.  I  suppose that could work; 
you can always troubleshoot client connections (inclusive the  ip acquiring   process, trough DHCP ) using : 
                       https://logadvisor.cisco.com/logadvisor/wireless/9800/9800ClientConnectivity

  These client debugs, so called RadioActive Traces can be analyzed with : Wireless Debug Analyzer

 M.

[Saikat Nandy]

Internal DHCP server of the controller is specifically meant for central switching - where client traffic is hitting the WLC interface. Another key thing - to run internal you need client vlan SVI to be present in the controller. That also means you can not keep the SVI on the remote branch switch and expect WLC internal DHCP to work.
There are 3 possible ways to achieve what you are trying - 
1. Put the APs from the remote site in local mode and do central switching - which will send all the client traffic back to the controller. Not a good option as your deployment is flex but you are bypassing the concept of flex.
2. Use central dhcp option.
3. Create a dhcp scope on the switch present in the remote site and use that switch as dhcp server - better and preferable option IMO.