DHCP stands for Dynamic Host Configuration Protocol. It is the critical feature on which the users of an enterprise network communicate. DHCP helps the enterprises to smoothly manage the allocation of IP addresses to the end-user clients’ devices such as desktops, laptops, cellphones, etc.
History
DHCP was used for the first time in 1993. It was built on the Bootstrap Protocol (BOOTP) of 1985. The definition of the Dynamic Host Configuration Protocol is in RFC 2131 and can be found under the UDP port numbers 67 and 68.
Basic Functioning
Upon dynamically configuring a device with dynamic IP from a DHCP server, three things come into play, the IP address (of course), subnet mask and the default gateway.
Configuring a DHCP server to hand out IP addresses on a subnet is known as a DHCP pool. This pool of addresses is usually a range of consecutive numbers within a single IP subnet. If any of the addresses within the range needs to be blocked, it can be done by the administrator. The subnet mask tells devices how large the subnetwork is that they are connected to; this is critical from a broadcast perspective. Finally, the default gateway is the IP address that signifies the exit point of the subnetwork to which the device belongs.
Characteristics
- Centralized and automated TCP/IP configuration.
- The efficient handling of IP address changes for clients that must be updated frequently, such as those for portable devices that move to different locations on a wireless network.
- The forwarding of initial DHCP messages by using a DHCP relay agent, which eliminates the need for a DHCP server on every subnet.
- The ability to define TCP/IP configurations from a central location.
DHCP Lease Time
In most cases, DHCP will work with default settings that largely are the same from server to server. However, different DHCP servers assign IP addresses for different periods of time before which it is altered with a fresh IP address on a particular end-device. In majority cases, the DHCP lease time is 14 days. However, with the growing number of users and mobile environments, the enterprises have found that their pool of available addresses can run out quickly.
To solve this, DHCP lease times can be reduced to stay with a specific device for a few hours or less. The process of determining optimal DHCP lease times depends on the type of users, the size of the DHCP subnets, and how much load the DHCP server can handle.
DHCP Relay Agent
A DHCP relay agent is a way for the network to listen to DHCP server discovery broadcast messages from client devices, convert broadcast requests into a unicast packet, and forward requests onto the DHCP server that’s in a different part of the network. This centralizes the management of IP addresses on the network.
Advantages
- Easy use and configuration, as the network parameters have to be entered only once.
- Furthermore, the existing IP addresses can be used optimally.
- Because of the frequently changed locations, it is almost impossible that mobile devices to configure themselves constantly. Here, the automatic DHCP system offers the advantage of uncomplicated and simple applicability.
Disadvantages
- The problem with DHCP is that clients accept any server. Accordingly, when another server is in the vicinity, the client may connect with this server, and this server may possibly send invalid data to the client.
- Security of MAC address is also not provided.