DHCP server in Kerio Control
Article Number: 1391 | Last Updated: Thu, Aug 25, 2016 9:01 AM
Kerio Control includes a DHCPserver. 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.
So called reservations can be also 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 host name. These clients will have fixed IP address.
Kerio Control also allows 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 groupsTrusted/Local Interfaces, Guest Interfaces and Other Interfaces. This implies that the only thing to do is actually to run the DHCP server.
Automatic configuration of scopes
By default, the DHCP server works in the mode of automatic configuration of scopes.
For each interface's subnet, a scope of the following parameters will be created:
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. However, bear in mind that changes of interfaces in group Trusted/Local Interfaces, Guest Interfaces and Other Interfaces (e.g.: adding of a new interface, change of IP address, etc.) require manual update of address scopes defined in the DHCP server.
Only one scope can be defined for each IP subnet.
In the administration interface, it is also possible to use a scope template where parameters are already predefined in accordance with the particular firewall's interface. For details, see above, section Automatic configuration of scopes.
Defining individual scopes
Kerio Control enables the administrator to define only one scope within each subnet. To create exclusions from this scope (for example for a group of servers with static IP addresses), follow these instructions:
Create the scope from 192.168.1.10 to 192.168.1.100 and click on the Exclusions button to define the scope from 192.168.1.50 to 192.168.1.60. These addresses will not be assigned by the DHCP server.
Leases and Reservations
Scopes can be viewed in the Leases and reservationstable.
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
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.
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 withnout typing it, if Kerio Control is able to see the MAC address of the host:
DHCP server of Kerio Control reserves the MAC address, if the DHCP server in Kerio Control is enabled and a scope of IP addresses is created on the interface.
If you use Kerio Control MAC Filter, check the Also permit MAC addresses used in DHCP reservations or automatic user login option.
If you want to check your settings, in the Status column appears Reserved, Leased.