What is DHCP ?

What is DHCP ?

Dynamic Host Configuration Protocol (DHCP) is a network management protocol used to automate the process of configuring devices on IP networks, thus allowing them to use network services such as DNS, NTP, and any communication protocol based on UDP or TCP. A DHCP server dynamically assigns an IP address and other network configuration parameters to each device on a network so they can communicate with other IP networks. DHCP is an enhancement of an older protocol called BOOTP.

Components of DHCP

When working with DHCP, it’s important to understand all of the components.  Below is a list of them and what they do:

  • DHCP server: A networked device running the DCHP service that holds IP addresses and related configuration information. This is most typically a server or a router but could be anything that acts as a host, such as an SD-WAN appliance.
  • DHCP client: The endpoint that receives configuration information from a DHCP server. This can be a computer, mobile device, IoT endpoint or anything else that requires connectivity to the network.  Most are configured to receive DHCP information by default.
  • IP address pool: The range of addresses that are available to DHCP clients. Addresses are typically handed out sequentially from lowest to highest.
  • Subnet: IP networks can be partitioned into segments known as subnets. Subnets help keep networks manageable.
  • Lease: The length of time for which a DHCP client holds the IP address information. When a lease expires, the client must renew it.
  • DHCP relay: A router or host that listens for client messages being broadcast on that network and then forwards them to a configured server. The server then sends responses back to the relay agent that passes them along to the client. This can be used to centralize DHCP servers instead of having a server on each subnet.

Benefits of DHCP

DHCP provides the following benefits.

  • Reliable IP address configuration. DHCP minimizes configuration errors caused by manual IP address configuration, such as typographical errors, or address conflicts caused by the assignment of an IP address to more than one computer at the same time.
  • Reduced network administration. DHCP includes the following features to reduce network administration:
    • Centralized and automated TCP/IP configuration.
    • The ability to define TCP/IP configurations from a central location.
    • The ability to assign a full range of additional TCP/IP configuration values by means of DHCP options.
    • 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.

Benefits or advantages of DHCP

Following are the benefits or advantages of DHCP:
➨DHCP is easy to implement and does automatic assignment of IP addresses to requesting clients. Hence manual configuration time of IP addresses can be reduced.
➨The implementation does not require any additional costs.
➨Duplicate or invalid assignment of IP addresses are prevented. Hence there is no chance of conflicts in IP addresses.
➨It simplifies administration of the network.
➨It supports multiple scopes e.g. multicast scope, super scope etc.
➨It has great benefit to mobile users as valid configuration parameters are automatically obtained from the new network.

 disadvantages of DHCP

Following are the disadvantages of DHCP:
➨DHCP server can be single point of failure in networks having only one configured DHCP server.
➨DHCP packets can not travel across router, Hence relay agent is necessary to have DHCP server handle all leases on both network segments. Relay agents receive broadcast DHCP packets and forward them as unicast packets to DHCP server. Here relay agent must be configured with IP address of the DHCP server.
➨Security: As DHCP server has no secure mechanism for authentication of the client, it can gain unauthorized access to IP addresses by presenting credentials such as client identifiers which belong to other DHCP clients.
➨The machine name does not change when new IP address is assigned.
➨Client is not able to access the network in the absence of the DHCP server.

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