Overview

Kerio Control includes a DHCP server. The DHCP server assigns clients IP addresses within a predefined scope for a certain period (lease time). If an IP address is to be kept, the client must request an extension on the period of time before the lease expires. If the client has not required an extension on the lease time, the IP address is considered free and can be assigned to another client. This is performed automatically and transparently.

Diagnosis

So-called reservations can be defined on the DHCP server — certain clients will have their own IP addresses reserved. Addresses can be reserved for a hardware address (MAC) or a hostname. These clients will have a fixed IP address.

Kerio Control also allows the automatic configuration of the DHCP server. This option involves automatic creation and updates of IP address ranges and parameters in accordance with network interfaces included in groups Trusted/Local Interfaces, Guest Interfaces, and Other Interfaces. This implies that the only thing to do is actually to run the DHCP server.

Solution

Automatic configuration of scopes

By default, the DHCP server works in the mode of automatic configuration of scopes.

Manual definition of Scopes and Reservations

If you do not want to use the automatic configuration of IP ranges, you can switch to the manual mode. For more information, please refer to the Manual Configuration of Scopes and Reservations in Kerio Control.

Leases and Reservations

Scopes can be viewed in the Leases and reservations table.

Using the Remove button you can release the selected IP address and/or cancel IP address reservation on the spot. DHCPRELEASE control message will be sent to the corresponding client.

Reserving an IP address

A DHCP server enables you to book an IP address for any host or MAC address. Reservations can be set in both scope configuration modes, manual and automatic. The act of adding a reservation in the automatic mode does not switch to manual mode.

Any IP address included in a defined subnet can be reserved. This address can (but does not have to) belong to the scope of addresses dynamically leased, and it can also belong to any scope used for exceptions.

Adding reservations

1. In the administration interface, go to the DHCP Server.
2. In the Leases and reservations table, click Add > Add Reservation.
3. Type the name of the reservation.
4. Select the MAC address or hostname for device identification and type the identification.
5. Type a reserved IP address.
   
6. Click OK.

If you want to check your settings, icons marked with R represent reserved addresses.

Making a DHCP reservation in Active Hosts

You can reserve an IP address for a MAC address without typing it if Kerio Control is able to see the MAC address of the host:

1. In the administration interface, go to Status > Active Hosts.
2. Select a host.
3. Right-click on the selected user and click Make DHCP Reservation by MAC.
   
4. Kerio Control opens an informational window about the new configuration.
   
5. Click OK.

DHCP server of Kerio Control reserves the MAC address if the DHCP server in Kerio Control is enabled and the scope of IP addresses is created on the interface.

Reserving leases

1. In the administration interface, go to the DHCP Server.
2. In the Leases and reservations table and click (highlight) the desired device with a leased address.
3. Click Add > Reserve lease.
   
4. In the dialog, click OK.

If you want to check your settings, in the Status column appears Reserved, Leased.