topic Re: C9800L External DHCP is not releasing IP in Wireless

C9800L External DHCP is not releasing IP

cjiwonder — Fri, 09 Feb 2024 05:17:54 GMT

C9800L is connected to the Core Switch 9500, and the AP is connected in VLAN 100. A VLAN 100 SVI has been created in the Core Switch and an IP helper has been configured. IP addresses are successfully being released in VLAN 100 without any issues. The IP address has also been released for the AP and it has joined with the controller. However, the WLC is not releasing an IP address for clients.

In the C9800L, VLAN 100 is configured, not SVI. The DHCP Server IP is enabled in the policy, but IPv4 DHCP required is disabled.

Please assist me in resolving this issue.

Re: C9800L External DHCP is not releasing IP

MHM Cisco World — Fri, 09 Feb 2024 06:28:08 GMT

SW 9500 the DHCP server in same subnet of client ?
if NOT you need dhcp reply in SW
MHM

Re: C9800L External DHCP is not releasing IP

cjiwonder — Fri, 09 Feb 2024 06:32:13 GMT

Yes, SW 9500, C9800L and the DHCP server are in the same subnet only.

Re: C9800L External DHCP is not releasing IP

MHM Cisco World — Fri, 09 Feb 2024 06:38:13 GMT

are you sure ?
are you saying AP and client in same subnet ?

MHM

Re: C9800L External DHCP is not releasing IP

cjiwonder — Fri, 09 Feb 2024 06:52:27 GMT

Core Switch 192.168.10.1/24, DHCP Server 192.168.10.2/24, WLC 192.168.10.3/24. All these 3 are in VLAN 10.

AP 192.168.100.1/24 (VLAN 100)

Re: C9800L External DHCP is not releasing IP

MHM Cisco World — Fri, 09 Feb 2024 06:52:46 GMT

and the clinet in which VLAN ?
it recommend that AP not in same VLAN of clinet but if it in same vlan then you need to add dhcp relay in VLAN 100 point to DHCP server in vlan 10 (192.168.10.2/24)
MHM

Re: C9800L External DHCP is not releasing IP

cjiwonder — Fri, 09 Feb 2024 07:11:02 GMT

Yes, AP and the client in the same VLAN. DHCP relay already configured in the Core Switch for SVI VLAN100.

Re: C9800L External DHCP is not releasing IP

MHM Cisco World — Fri, 09 Feb 2024 07:35:42 GMT

in SW do

show ip dhcp server statistics

Re: C9800L External DHCP is not releasing IP

Mark Elsen — Fri, 09 Feb 2024 08:21:43 GMT

- Use these recommended setups for providing dhcp services : https://www.cisco.com/c/en/us/products/collateral/wireless/catalyst-9800-series-wireless-controllers/guide-c07-743627.html#DHCPRequiredoption

https://www.cisco.com/c/en/us/products/collateral/wireless/catalyst-9800-series-wireless-controllers/guide-c07-743627.html#DHCPbridgingandDHCPrelay

Re: C9800L External DHCP is not releasing IP

Rich R — Mon, 19 Feb 2024 10:57:09 GMT

@cjiwonder you cannot relay DHCP twice.
If you are doing the DHCP relay on the switch then you should not configure any DHCP config on the WLC other than DHCP required which is done by snooping client DHCP and not allowing client to RUN state until it completes DHCP. The WLC simply bridges the DHCP broadcasts to the VLAN and your switch handles the DHCP relay. Remove any DHCP relay config from the WLC.

As @MHM Cisco World says it is not best practice to put clients and AP management in the same VLAN. Your clients should be in a separate VLAN from the APs.

Re: C9800L External DHCP is not releasing IP

cjiwonder — Mon, 12 Feb 2024 03:38:33 GMT

No DHCP relay in WLC, No DHCP server and enabled "IPv4 DHCP required". in the policy. AP and the clients are in different VLAN but still issue persists.

Core Switch 192.168.10.1/24, DHCP Server 192.168.10.2/24, WLC 192.168.10.3/24. All these 3 are in VLAN 10.

AP 192.168.100.1/24 (VLAN 100) and client 192.168.20.x/24 (VLAN 20), also created VLAN 20 in the WLC.

Re: C9800L External DHCP is not releasing IP

cjiwonder — Mon, 19 Feb 2024 09:31:03 GMT

My issues is still pending, can anyone please help me to resolve this issue?

Re: C9800L External DHCP is not releasing IP

Mark Elsen — Mon, 19 Feb 2024 10:22:23 GMT

>....My issues is still pending, can anyone please help me to resolve this issue?
- As the community is populated by Cisco customers on a volunteering basis ; for resolving business needs use Cisco official support and or contact TAC ,

Re: C9800L External DHCP is not releasing IP

Rich R — Mon, 19 Feb 2024 11:39:26 GMT

Have you already followed the advice provided?

As @Mark Elsen says we have very little information to work on from the limited information provided and we cannot do real-time troubleshooting with you. If you need urgent technical assistance get a Cisco expert in to help you or contact Cisco TAC. However TAC are going to start with the same expectation that you have followed Cisco's Best Practice and design guidelines and are using up to date, supported software versions.

Re: C9800L External DHCP is not releasing IP

cjiwonder — Tue, 20 Feb 2024 09:28:40 GMT

I feel it is switch configuration issue, can anyone please verify my configuration.

Core Switch 192.168.10.1/24 (Trunk), DHCP Server 192.168.10.2/24 (Trunk), WLC 192.168.10.3/24 (Trunk). All these 3 are in VLAN 10.

AP 192.168.20.1/24 (Trunk, Native VLAN 20) and client 192.168.30.x/24 (VLAN 30), also created VLAN 30 in the WLC.

Re: C9800L External DHCP is not releasing IP

cjiwonder — Wed, 21 Feb 2024 08:42:00 GMT

Wireless Analyzer says "IPLEARN_CONNECT_TIMEOUT"