Catalyst WLC 9800 clients do not receive DHCP address from DHCP server

[aastes]

Hello all,

I'm setting up a new Catalyst 9115AXI-B with an embedded wireless controller C9800 and am having some trouble getting my wireless clients to get any DHCP information from my external DHCP server. The server is a Windows Server 2019 domain controller. The WLC can reach the domain controller and even synch with the server for DNS and NTP information, but not DHCP.

The switchport that the Catalyst is connected to is configured to be a trunk port with the correct VLAN permitted and set as its PVID (non-cisco switch if that matters).

Below are the configuration settings for the GigabitEthernet0 interface:

interface GigabitEthernet0
mac-address 0000.5e00.0101
ip dhcp relay information trusted
ip dhcp client client-id GigabitEthernet0
ip dhcp client broadcast-flag clear
ip address 10.57.252.250 255.255.255.0
ip helper-address 10.57.252.10
no negotiation auto
ipv6 traffic-filter implicit_deny_v6 in
ipv6 traffic-filter implicit_deny_v6 out

As well as the ip dhcp-server commands entered in global config mode:

ip name-server 10.57.252.10 10.57.252.3
ip dhcp-server 10.57.252.10
ip dhcp-server 10.57.252.3

Any help would be appreciated. Thanks. 

[Rich R]

EWC is not a WLC - the key difference is that it does not support central switching at all, only flexconnect local switching so client traffic (including DHCP) never transits the EWC WLC.  And the EWC interface does not support VLANs at all either, it's purely a management interface for the AP to join and you to access the EWC.

So any config you put on the EWC relating to DHCP relay or helper address will not work even if the commands are accepted.  And as per the best practice guide (link below) even on real 9800 WLC SVI interfaces (which are required for DHCP relay on WLC) are not recommended.  It's always recommended to bridge the wireless traffic at layer 2 and have the next hop switch/router handle the layer 3 functions including DHCP.

The EWC WLC and AP components operate like separate virtual machines on the AP.  The only way to switch that traffic is direct from the AP onto the VLAN and the DHCP must be handled by the next hop switch or router on that VLAN.

[aastes]

How do I bridge the L2 traffic so my router handles DHCP packets? Will that forward them to my Windows DHCP server?

[marce1000]

  - Why does there need to be a router in the story , on the VLAN SVI you can also configure ip helper-address x.x.x.x ; the latter being the address of the Windows DHCP server ,

 M.

[aastes]

Doesn't work. Thanks. 

[Rich R]

As per my explanation above EWC will not support any kind of DHCP relay.
How you configure your router depends on what type of router it is and what version of software it's running.
The VLAN mapping for the flexconnect local switched WLAN is done on the flex profile.

[MHM Cisco World]

No dhcp in Embedded WLC

The dhcp from host broadcast to vlan and if dhcp in same vlan then it must recieve dhcp request.

No need ip dhcp no need relay config.

If the dhcp server in other vlan you need to config dhcp relay in connect SW not in controller.

[marce1000]

                                                        >...Doesn't work. Thanks. 
  - You won't get very far on this forum (populated with technical specialists)  with conclusions like that ; a minimum added value would be to specify what was tried in detail (e.g.). It also seems more and more advised that you need to expand your basic knowledge on networking and dhcp setups , such as providing central dhcp service(s) on networks with multiple vlans (let alone the wireless infrastructure)

 M.