Cannot get ip address from remote dhcp

[interfacedy]

Please see the below diagram. WLC9800 is connected to the router via vlan20 and AP is connected to the router via vlan200. AP is joined to the wlc. The client can get ip address if dhcp server is configured at the wlc as internal. But the client cannot get ip address if a dhcp server is connected to sw2 even if ip helper-address is set at the wlc and pointed to the dhcp server. Any suggestions? Thanks

             Vlan20                                                       vlan200

WLC ----------- sw1 ---- Router -------------sw2------- AP . . . . . .  client

[balaji.bandi]

As Long as DHCP reachable Client should get DHCP IP address from DHCP Server, is the DHCP Server ( MS ?) what DHCP Server ?

what is the Logs shows ?

[MHM Cisco World]

the Mode of WLC handle the DHCP is different,
bridge mode make WLC re-send the broadcast and this need ip helper if the DHCP server in different VLAN and client 
Proxy Mode make WLC generate unicast toward the DHCP server, no need for ip helper. 

I think you use bridge without the ip helper in Router.