Client disconnect when they renew DHCP lease

[SKVN]

HI All,

Recently moved from the 2500 WLC to the 9800 WLC, Since after clients are disconnected when its time for a device to renew its dhcp lease. DHCP are locally managed server. Other branch who using same WLC doesn't have any issue. 

Once end user disconnect we should need either reboot PC or forcing a renewal through the cmd prompt.

Did anyone know about this issue ?

[marce1000]

 - Should not happen ; start with a checkup of the  9800 WLC configuration using the CLI command
    show tech wireless  (not a simple show tech) and feed the output from that into Wireless Config Analyzer

 M.

[MHM Cisco World]

can you check in which status the client is pending 

MHM

[SKVN]

Wireless Config Analyzer Seems like this is not working page 

[marce1000]

 - @SKVN wrote ; Wireless Config Analyzer Seems like this is not working page 
                            It is working  , at least here for me ; remember to use as input the CLI
                           output from a show tech wireless

                           Or else post a screenshot of what you are currently seeing

 M.

[Flavio Miranda]

@SKVN 

 Which authentication method are you using? Keep in mind that clients first authenticate and then request IP address (except for guest).
 Can you share a debug from one client with the whole conversation? 

[JPavonM]

Check if you have configured "DHCP required" under the advanced settings in the Policy profile, that tells the AP to disconnect the client if no DHCP packet is seen when connecting to it (initial connection or roaming). Have you checked if anytime the client renew the DHCP lease if moves to another AP?

[SKVN]

@JPavonM  Yes i do see "DHCP required" is configured. So do we need to disable that option ?

[MHM Cisco World]

what is the state of client?? 

[JPavonM]

I always disable all vendor features, and this DHCP required is one of them.

Non-standard features could have unwanted side effects in connectivity, and in this case, this lost of connectivity when roaming is the most critical one, specially if the users are using conferencing/audio apps.

[Rich R]

We use "DHCP required" pretty much everywhere on guest WiFi and others and it's never been a problem on AireOS or 9800. (it's only turned off in specific cases where we allow static IPs)

What version of software are you using? See TAC recommended link below.

Check the WLC config as Marce advised.  https://cway.cisco.com/wireless-config-analyzer/ working fine for me.  As already highlighted you must use the raw output from "show tech wireless" on the WLC.  Save to text file and upload to the tool.  Do NOT use an editor which adds line numbers or formatting to the output.

That will highlight dozens of common mistakes people make on the WLC config and also highlight some best practices.  You should also read the Best Practices guide yourself - link below.

ps: The only time I've seen clients having a problem with renewing DHCP lease was when corporate IT pushed a new Windows firewall policy that prevented the clients from renewing leases so the lease had to expire then the client had to start DORA all over again causing severe disruption.

[MHM Cisco World]

totally agree 
the only case you disable dhcp require is for static IP endpoint like Printer, which dont use DHCP and hence WLC can not know the endpoint IP

MHM