DHCP leases

[lpacukovski]

After revoking a DHCP lease from one device, the same IP is given to another as a static, but it never shows back up in the list. The device is online for a period of time, and then drops off the network. I can't make a reservation on the IP. Any ideas? Thank you

[oarslan]

Hi,

What is FortiOS version ?

[akileshc]

Good Day, lpacukovski

You can use DHCP to bind an IP address to a specified MAC address to prevent users in the from changing their IP addresses and generating IP address conflicts or unauthorized usage of IP addresses.

For further details, please see the following link: 

** https://docs.fortinet.com/document/fortigate/6.0.0/handbook/876572/assigning-ip-address-by-mac-addre...

If you want to increase the duration in seconds that a conflicting IP address is removed from the DHCP range before it may be reused, use the following CLI commands to increase the timer:

# config sys dhcp server

# edit "ID"

# set conflicted-ip-timeout "Value in seconds" -> Enter an integer value from <60> to <8640000> (default = <1800>)

# end

I hope this helps you meet your requirements.