topic Re: DHCP client wont get ip from C9800 LC in Wireless

DHCP client wont get ip from C9800 LC

AliDoskii — Fri, 29 Nov 2024 11:19:59 GMT

Hello Cisco Community,

Hope everyone is well.

Recently i am facing difficulty with implementing my wireless network.
i have installed wireless access point and all of them successfully appearing in my wireless controller dashboard, WLAN created for them and SSID is working fine, i could see and connect to my SSID without problem.

The only problem that i have is, my wireless client cannot get ip address from DHCP.

I have made VLAN 50 to be relay as well but still no chance, whereas access point is getting ip address from DHCP without any problem.

can someone please help me with that?
Thanks in advance,
AliDoski

Re: DHCP client wont get ip from C9800 LC

Mark Elsen — Fri, 29 Nov 2024 11:19:39 GMT

- Start with a checkup of the C9800 configuration using the CLI command show tech wireless and feed the output from
that into Wireless Config Analyzer
(do not use a simple show tech as input for WirelessAnalyzer ; use the full command in green)

- Further engage in full client debugging according to https://logadvisor.cisco.com/logadvisor/wireless/9800/9800ClientConnectivity , these debugs can be analyzed with Wireless Debug Analyzer

- - Outputs from the commands mentioned in https://www.cisco.com/c/en/us/support/docs/wireless/catalyst-9800-series-wireless-controllers/217738-monitor-catalyst-9800-kpis-key-performa.html#anc5 can also be useful , especially when changes are made to the configuration

- Use this architecture for DHCP https://www.cisco.com/c/en/us/td/docs/wireless/controller/9800/technical-reference/c9800-best-practices.html#DHCPbridgingandDHCPrelay

- Look into the controller software version , go for 17.12.3 , especially if you are currently on an older version ,

Re: DHCP client wont get ip from C9800 LC

Flavio Miranda — Fri, 29 Nov 2024 11:27:29 GMT

@AliDoskii

Assuming you using Local mode and not flexconnect. Can you ping the WLC IP address on vlan 50 from the DHCP server?

Or, can you ping the DHCP server from the WLC?

Re: DHCP client wont get ip from C9800 LC

AliDoskii — Fri, 29 Nov 2024 11:36:39 GMT

@Flavio Miranda
DHCP server is same as default gateway, yes i could ping without issue.
and yes, all my APs are operating in local mode as shown.

AP are getting IP from DHCP with no issue:

Re: DHCP client wont get ip from C9800 LC

shambhu.kumar — Fri, 29 Nov 2024 12:01:38 GMT

Please check,

show run all | in dhcp
service dhcp

if not enable, please enable dhcp service

config t

service dhcp

Re: DHCP client wont get ip from C9800 LC

Flavio Miranda — Fri, 29 Nov 2024 12:07:11 GMT

Wlan is mapped to vlan 50 on WLC?

Re: DHCP client wont get ip from C9800 LC

AliDoskii — Fri, 29 Nov 2024 12:24:01 GMT

How can i verify this?

Re: DHCP client wont get ip from C9800 LC

AliDoskii — Fri, 29 Nov 2024 12:26:57 GMT

i checked this before and enabled previously.

Re: DHCP client wont get ip from C9800 LC

Flavio Miranda — Fri, 29 Nov 2024 12:29:08 GMT

show wlan summary

Re: DHCP client wont get ip from C9800 LC

MHM Cisco World — Fri, 29 Nov 2024 12:34:05 GMT

In wlc monitoring > client check in which state the wifi endpoint pending

MHM

Re: DHCP client wont get ip from C9800 LC

AliDoskii — Fri, 29 Nov 2024 12:44:59 GMT

Here is my WLAN config :
WLC(config-wlan)#do show run wlan
!
aaa attribute list wlan_lobby_access
policy-map AutoQos-4.0-wlan-Port-Output-Policy
class AutoQos-4.0-Output-CAPWAP-C-Class
priority level 1
class AutoQos-4.0-Output-Voice-Class
priority level 2
class class-default
service-policy output AutoQos-4.0-wlan-Port-Output-Policy
service-policy output AutoQos-4.0-wlan-Port-Output-Policy
service-policy output AutoQos-4.0-wlan-Port-Output-Policy
service-policy output AutoQos-4.0-wlan-Port-Output-Policy
service-policy output AutoQos-4.0-wlan-Port-Output-Policy
wlan Radisson policy Radisson
wlan Radisson 1 Radisson-Starlink
security wpa psk set-key ascii 0 ciscocisco
no security wpa akm dot1x
security wpa akm psk
security pmf optional
no shutdown
!

Re: DHCP client wont get ip from C9800 LC

Flavio Miranda — Fri, 29 Nov 2024 12:46:35 GMT

I was expecting a different output from this command. Take a look on this video and make sure you went through all the steps. On this video the dude show how to map WLAN to VLAN and setup DHCP server on the WLAN.

https://www.youtube.com/watch?v=5FpYS_rphik

Re: DHCP client wont get ip from C9800 LC

AliDoskii — Fri, 29 Nov 2024 12:52:40 GMT

i believe i made a mistake at the initial config of my controller in policy section of WLAN creation i chose default VLAN instead of VLAN 50.

Re: DHCP client wont get ip from C9800 LC

Flavio Miranda — Fri, 29 Nov 2024 12:57:25 GMT

That might be something like this. The WLC is not placing the DHCP request on the right vlan. Check the DHCP server is rihgt configured on the WLAN also.

Re: DHCP client wont get ip from C9800 LC

AliDoskii — Fri, 29 Nov 2024 15:15:13 GMT

I have changed WLAN VLAN to 50 as previously was default 1.
and i have configured server DHCP in policy and put my server DHCP 10.10.50.1 and removed ip helper address under vlan 50 as they are all in some subnet.

but still my wireless users cannot get ip address from dhcp.

Re: DHCP client wont get ip from C9800 LC

Mark Elsen — Fri, 29 Nov 2024 15:18:42 GMT

- May I still remind you to execute the WirelessAnalyzer procedure when making configuration changes on the controller :
using the CLI command show tech wireless and feed the output from
that into Wireless Config Analyzer
(do not use a simple show tech as input for WirelessAnalyzer ; use the full command in green)

Consider mandatory after configuring has been done !!

Re: DHCP client wont get ip from C9800 LC

Flavio Miranda — Fri, 29 Nov 2024 15:44:09 GMT

Clients can authenticate?

I would change your design and remove the SVI from WLC and put It in the core keeping the interface in trunk mode.

I believe WLC as layer3 is not recommend

Re: DHCP client wont get ip from C9800 LC

Rich R — Fri, 29 Nov 2024 16:05:35 GMT

service dhcp is only required if you are using the WLC as a DHCP server, which you are not as far as I can tell.

According to the diagram the Microtik router is the DHCP server right?

Re: DHCP client wont get ip from C9800 LC

Rich R — Fri, 29 Nov 2024 16:04:48 GMT

Yes that policy is definitely a problem - your policy was completely empty in the config above but should be fine once configured with vlan 50!

You DO NOT need DHCP relay at all (either interface helper address or in policy) when the DHCP server is in the local connected subnet!

You do not need the SVI (vlan 50 interface) at all and in fact it is NOT RECOMMENDED on 9800:
https://www.cisco.com/c/en/us/td/docs/wireless/controller/9800/technical-reference/c9800-best-practices.html#DHCPbridgingandDHCPrelay

So remove all references to the DHCP server on the WLC, delete the SVI and allow the client traffic to be bridged to vlan 50 and the router to respond.

Re: DHCP client wont get ip from C9800 LC

AliDoskii — Fri, 29 Nov 2024 16:57:55 GMT

yes client can authenticate.

i removed SVI but now access point cannot discover controller.