topic Re: WLAN client lost their ip address ? in Network Access Control

WLAN client lost their ip address ?

879205607 — Mon, 24 Apr 2023 03:47:59 GMT

I have created an SSID and enable 802.1x authentication ，assign ip addresses to clients via dhcp.

However, I found that after some clients have been connected to the network for a while, their DHCP ip addresses will be lost and become 169.254.x.x ?

Re: WLAN client lost their ip address ?

Arne Bier — Mon, 24 Apr 2023 04:38:16 GMT

that usually indicates that 802.1X was successful, but that DHCP requests are not reaching the DHCP server. Is this AireOS or 9800?

Re: WLAN client lost their ip address ?

879205607 — Mon, 24 Apr 2023 08:42:29 GMT

Hi,

The controller is Cisco 2504.

But i am sure that DHCP server is reachable, because when the client is connected to the network, I see that the client does get the IP address and can access the network resources. However, after about half an hour, the client's ip address is lost

I think may be session-timeout settings?

Re: WLAN client lost their ip address ?

Arne Bier — Mon, 24 Apr 2023 09:02:15 GMT

Does that also correlate with the DHCP lease time for that scope? Usually DHCP renew is 50% of the lease time.
Either way, even if the lease time was short, there should be no ACL in place to prevent DHCP traffic. Are you assigning an ACL to the client after successful authentication?

Session timeout is not an issue. It just ensures that the client is forced the re-auth. And then the whole process starts again.
If you suspect that 802.1X is the issue then clone the WLAN config and make it PSK instead. Make sure everything else is identical (VLAN etc). And then see how the client behaves.

Re: WLAN client lost their ip address ?

poongarg — Mon, 24 Apr 2023 09:53:35 GMT

In such case, I would suggest to take OTA captures (using sniffer option on the MAC Book) along with debugs on AP and WLC to figure out the root cause. If the client got disconnected and post that it is not able to get ip address? Any new authentication seen on ISE just before the ip address is lost. If the client remain connected to the previous SSID?

Re: WLAN client lost their ip address ?

ahollifield — Tue, 25 Apr 2023 22:43:19 GMT

Also: https://www.cisco.com/c/en/us/products/collateral/wireless/2504-wireless-controller/eos-eol-notice-c51-740645.html

Re: WLAN client lost their ip address ?

879205607 — Wed, 26 Apr 2023 09:56:02 GMT

Hello All,

I adjusted the SSID session-timeout to 86400 seconds and the problem doesn't seem to be recurring。

It looks like the problem is related to the Intel AX201 wireless network adapter.

https://community.intel.com/t5/Wireless/Intel-WiFi6-AX201-160Mhz-L3-Issues-with-RADIUS-Authentication/td-p/1324596

Re: WLAN client lost their ip address ?

Arne Bier — Wed, 26 Apr 2023 20:28:47 GMT

What happens after 86400 seconds? I guess most users won't be on the network that long?

#problemsweptunderthecarpet 🙂

Re: WLAN client lost their ip address ?

879205607 — Fri, 28 Apr 2023 02:58:22 GMT

I'm not sure, because no user will be connected to the wireless network for up to 24 hours, because usually their computer will hibernate when not in operation.

But the loss of IP addresses did disappear

Re: WLAN client lost their ip address ?

Dustin Anderson — Fri, 28 Apr 2023 13:50:13 GMT

To put some context, we have seen that Intel seems to ping the default gateway and if it seems to loose 3 pings will trigger DHCP again. I think this is how they detect vlan changes. This would explain why when the session timed out if it didn't reauth, it would loose access and kick off DHCP.