Catalyst 9800 disallow clients from manually assinging IP address

[jasonmeyer]

Pretty sure this was an option on the old 8510, but not sure where to look on the 9800. Had a client manually give itself the gateway address of the subnet which made things really fun. And yes, the IP address is excluded from use on the DHCP server. 

[Scott Fella]

Its under the tags, you can use this link also which shows where the option is located.
https://www.cisco.com/c/en/us/td/docs/wireless/controller/9800/config-guide/b_wl_16_10_cg/dhcp-for-wlans.html

Configuring the Internal DHCP Server Under a Wireless Policy Profile (GUI)

Procedure

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Step 1	Choose Configuration > Tags & Profiles > Policy.
Step 2	Click a policy name.
Step 3	Click the Advanced tab.
Step 4	Under DHCP settings, check or uncheck the IPv4 DHCP Required check box and enter the DHCP Server IP Address.
Step 5	Click Update & Apply to Device.

[jasonmeyer]

That has been done. The checkbox is unchecked and there is an IP address for my internal DHCP server.

[Scott Fella · Accepted solution]

If you don't want a user to enter a static, you would need DHCP required checked.  The DHCP server IP is optional.  Having the box unchecked will allow static address.