IP Address Assignment

Dynamic Host Configuration Protocol (DHCP) is a protocol that allows the automatic assignment of IPv4 addresses to connecting hosts and clients. The task of assigning addresses to connecting DHCP clients is performed by a DHCP Server. The Clavister NetShield Firewall can behave as a DHCP server.

With DHCP, assigned addresses come from a predefined IPv4 address pool which the DHCP server manages. When the server receives a DHCP request, it returns a set of parameters to the client in a unicast message. These parameters typically include assigned IPv4 addresses, MAC address, domain name, and a DHCP Lease.

DHCP Leases

Compared to static IP assignment where the client can be said to own the address, a DHCP server leases addresses to each client for a predefined period of time. During the lifetime of the lease, the client has permission to keep the assigned address and is guaranteed to have no address collision with other clients which also receive leases from the same DHCP server.

Lease Expiration

Before the expiration of a lease, the client must renew the lease from the server in order to keep using assigned IPv4 addresses. Alternatively, the client may decide at any time that it no longer requires a lease and can terminate it, releasing IP addresses back to the pool.

The lease time can be configured in the DHCP server by the administrator.