WLC 9800 DHCP relay problem

[Calin Cristea]

Hi,

I have a new WLC 9800CL with OS 17.6.4. I have setup a SSID, i have configured the default-policy-profile (from tags and profiles /policy menu) , in the Advanced Menu, i have checked  IPv4 DHCP Required  button, and on DHCP Server IP Address, i have added  the DHCP Server. Still, clients are not able to get a dhcp ip address from the external DHCP Server.

WLC and DHCP Server are from the same subnet, but the lease ip`s for clients are from a different subnet.

Is there anyway i can do this? I have read about adding from Layer 2 /Vlan SVI an ip address and add there DHCP relay, but  i want to do this from policy menu.

Clients are not getting and ip address, and status is ip learn.

[marce1000]

 -  Review the WLC 9800 current configuration with the CLI command : show  tech   wireless , have the output analyzed by  https://cway.cisco.com/tools/WirelessAnalyzer/  , please note do not use classical show tech-support (short version) , use the command denoted in green for Wireless Analyzer.               Checkout all advisories!  All items red-flagged should be corrected. For future use : WirelessAnalyzer can also make you aware of the RF environment such as coverage holes , APs under heavy load , APs undergoing frequent channel changes and so on. It is advised to use WirelessAnalyzer on a regular basis afterwards, also meaning it could be done now-already too!

 M.

[Calin Cristea]

Thank you Marce, this is indeed useful information, but it does not helping me solving my problem. I`ve tried you`re debug uploaded, but it does not show me how to fix my dhcp issue.

[kamalovresid]

Hello everyone. I have a little trouble about virtual cisco 9800 wirelless lan controller. I installed virtuall cisco 9800 wlc on esxi 8.0 and I added my real cisco ap to the virtual wlc.And then I configured wireless configuration as a flex mode ap but clients are unable to join to the my ssid. I have a real fortigate firewall and this firewall conneted to the cisco sw. Internet and other vlan connected to the sw by firewall. I configured 2 interface on sw. One of them as trunk which one is connect to the wlc and other one as access mode connect to the ap. Could you help me about this problem?I mean, clients are unable to join to the ssid,clients cannot join to the ssid.

[Sandeep Choudhary]

In the policy filed you dont need to assign the DHCP server IP. Just add IP helper command under the vlan from whcih wireless clinet will get the IPs.

Example:

Int vlan 99

ip address <>

ip helper-address <dhcp ip address>

Regards

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[Calin Cristea]

I need to add some information. This setup is an upgrade, now i have  a 2504 controller with 1700 access points. In this scenarion, no ip dhcp relay or proxy was setup. Only on the router lan (gateway) interface - ip helper address pointing to DHCP Server. 
I am replacing old 2504 WLC and AP`s with CL9800 controller and 9115 AP`s. I want to keep the same scenario. I have several geographical locations with access points connected to this controller . Can i do this without SVI ?

[Sandeep Choudhary]

Yes you can do without SVI on WLC.

Regards

Dont forget to rate helpful posts

[JPavonM]

The comment from @Sandeep Choudhary  was to add that command to the SVI in the router/L3 switch and not the WLC, so yes you can continue with your previous setup.

Furthermore, let me share something I've learned by hard with the "DHCP required" feature. Whenever a client roam from one AP to another, this DHCP requirement is imposed so the client will re-vallidate the DHCP lease. In some scenarios, mainly with real-time traffic like Zoom or Teams, but also others, this could cause a drop in the traffic. So if the user is on an active conversation (video or audio) that feature would make the conection to drop for a really short time but noticiable by the user, so they will complain. My recommendation, do not enable "DHP Required" feature, specially to SSIDs with that real-time traffic expectations.

[Calin Cristea · Accepted solution]

I have figured it out. From tags and profiles, needed to uncheck central switching and central dhcp.

The access point needed to be setup as flex , not local. From Tags and Profiles/Site, needed to uncheck enable local site.

After, clients were able to get an ip address. Problem solved.