I configured a VLAN for a group that I will have restricted internet access. I have a machine with a DHCP reservation on that VLAN. I have the DHCP lease set to 2 minutes. I disabled then enabled DHCP server. Disabled, rebooted, enabled DHCP server. It has been over an hour and the machine is still getting the original IP address. How can I force the machines to get a new IP access without contacting every end user and have them reboot?
Addresses are issued by the DHCP server, at the request of the device. If the device doesn’t ask for it, nothing happens. Your device already has an IP so it has no reason the DHCP server for another. Rebooting the DHCP server does nothing.
The lease time simply means how long after the IP becomes inactive, before the DHCP allows that IP to be reused by a different device. Once you set a reservation, that IP becomes an infinite lease time.
You need to force the LAN device to ask for an IP again. When the device asks, the DHCP server will issue the reserved address. On most Windows PCs, that happens if you simply unplug and reconnect the LAN cable. Or go into the Properties for the LAN adapter, and disable/enable it. Or open a DOS box and type in “ipconfig /renew”. Or of course reboot the device.
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