topic Re: DHCP FAILURE in Wireless

DHCP FAILURE

Benkip — Fri, 05 Jan 2024 11:40:20 GMT

Dear Experts,

I am experiencing below DHCP error on some clients will connecting on Wi-Fi. Anyone with a solution to the issue.

"Client made a request to the DHCP server, but the DHCP server rejected the client's request.server_ip='192.168.X.X' vlan_id='40' details='dhcp_nack' radio='1' vap='0' channel='44' rssi='22'"

Re: DHCP FAILURE

Mark Elsen — Fri, 05 Jan 2024 13:07:00 GMT

- Check this discussion https://www.reddit.com/r/meraki/comments/11mtrc8/sporadic_dhcp_issues/

Re: DHCP FAILURE

Benkip — Fri, 05 Jan 2024 13:27:34 GMT

Hi Marce, Thanks for the insight. I actually have a small number of devices (less than 200). On the network, we have a guest ssid with dhcp functionality that runs on the core switches. I will give it a try but I doubt if that will be the cause of the issue. When I connect device using cable on the same Vlan as the dhcp server, the devices connect immediately.

Re: DHCP FAILURE

CMR — Fri, 05 Jan 2024 14:17:23 GMT

Are you setting DHCP relay on a Meraki switch? There are a number of bugs and fixes about that. What switch model(s) and firmware are you using.

Re: DHCP FAILURE

Benkip — Fri, 05 Jan 2024 14:25:17 GMT

Yes, using dhcp relay.

Switch model - ms210-24p

Firmware Version: MS 15.22

Will really appreciate the fixes.

Re: DHCP FAILURE

CMR — Fri, 05 Jan 2024 14:28:37 GMT

The bug was for MS120 switches, so I think this might be something else, sorry.

Re: DHCP FAILURE

Benkip — Fri, 05 Jan 2024 14:31:50 GMT

May be it can help, actually access switch that connect to the APs are MS120 and all running 15.22. The coreswitch is MS210.

Re: DHCP FAILURE

CMR — Fri, 05 Jan 2024 16:19:45 GMT

It looks like you have the fixed version...

Re: DHCP FAILURE

Benkip — Fri, 05 Jan 2024 17:06:56 GMT

Noted and thanks Cmr

Re: DHCP FAILURE

BlakeRichardson — Sun, 07 Jan 2024 21:16:54 GMT

Is your DHCP lease pool large enough? Private MAC if enabled on devices can exhaust a DHCP lease pool very quickly if you have a few users and long DHCP lease times.

Re: DHCP FAILURE

Benkip — Mon, 08 Jan 2024 05:39:36 GMT

Thanks Blake. DHCP lease pool is large. I am using less than 50%. I did reduce the DHCP lease time to 8 hours. I am still getting logs with the same error. Private MAC is disabled as well.

Re: DHCP FAILURE

Rimccart — Wed, 10 Jan 2024 22:39:21 GMT

Hi Benkip,

The logs for the DHCP server rejection is curious. What are the DHCP server logs indicating when the wireless client is attempting to connect to the network? If a capture is taken at the DHCP server to the DHCP server switch port is the NAK originating from the server? Did the update to MS15.22 alleviate the believed unexpected behavior that was being hit?

Re: DHCP FAILURE

Benkip — Thu, 11 Jan 2024 06:24:33 GMT

Hi Rimccart,

We are still experiencing the same issue.

We had two dhcp servers on active active mode initially enabled for the affected SSID. From packet capture on the ports dhcp servers, ACK messages were only being received from on server. We deactivated the active active mode on dhcp and relay to the only one dhcp server were getting ACK messages from.

Firmware update did not also help.

Thanks.

Re: DHCP FAILURE

Rimccart — Thu, 11 Jan 2024 16:58:16 GMT

Hi Benkip,

It sounds like this is only impacting one SSID, correct?

If this is only impacting a particular SSID are there any settings on this SSID that drastically differ from the others? This could be the SSID configurations or the RF profile settings as well if the bitrates are set per SSID.

When we see this DHCP failure log in Meraki have we examined the impacted client's timeline as well?

Were there any additional events just before this DHCP failure, such as roaming or disconnection events?

Re: DHCP FAILURE

Benkip — Fri, 12 Jan 2024 05:55:53 GMT

Hi Rimccart, The NAK messages disappeared today after changing the dhcp port from trunk to access. I had configured the port that connect the dhcp server to trunk with native vlan 1. I think the dhcp server was responding to numerous dhcp requests from different vlans while on trunk hence generating the NAK messages. Happy this has resolved the issue. Thank you very much for your input.