Dhcp bootp relationship

In the previous article, we learned about the BOOTP protocol. Here we will mainly explain some content and relationships between dhcp bootp. Hope to help you.

Dhcp bootp protocol Similarity

Because of the relationship between the BOOTP protocol and DHCP protocol, the two Protocols share some defined features. Common elements include:

◆ Format structure used by each protocol to exchange messages between the server and client

BOOTP and DHCP use almost the same request message sent by the client) and reply message sent by the server ). Messages in any Protocol use a single 576-byte User Datagram Protocol (UDP) to encapsulate messages in each protocol. The message header is the same for BOOTP and DHCP. The only exception is that the last header field is used to transmit optional data. For BOOTP, this optional field is called the supplier-specific region and is limited to 64 eight-bit bytes. For DHCP, this region is called an option field and can contain up to 312 eight-byte DHCP option information.

◆ Use a well-known UDP port for Client/Server Communication

Dhcp bootp uses the same reserved protocol port to send and receive messages between the server and the client. Both BOOTP and DHCP servers use UDP port 67 to listen for and receive client request messages. BOOTP and DHCP clients generally reserve UDP port 68 for receiving message replies from the BOOTP server or DHCP server.

Because DHCP and BOOTP messages use almost the same format type and packet structure, and generally use the same service port as we all know, therefore, BOOTP and DHCP relay agents generally treat BOOTP and DHCP messages as basically the same message type without distinction.

◆ IP Address allocation as a complete Part of the Configuration Service

Although both BOOTP and DHCP allocate IP addresses to clients during startup, they use different allocation methods. BOOTP usually provides a fixed allocation of a single IP address for each client, which is permanently reserved in the BOOTP Server database. DHCP usually provides dynamic and lease allocation of available IP addresses. Each DHCP Client address is temporarily reserved in the DHCP server database.

Dhcp bootp differences

BOOTP and DHCP have obvious differences in host configuration methods. The following table compares the features of the two Protocols.

DHCP BOOTP

Designed before DHCP. Designed after BOOTP.

Plan to configure diskless workstation with limited boot capabilities. You plan to configure a networked computer with frequent reallocation and local hard drive and full boot capabilities, such as a portable computer ).

Dynamic BOOTP has a default expiration time of 30 days for IP address rent. DHCP has an expiration time of 8 days for IP address leasing.

Supports a limited number of client configuration parameters called vendor extensions. Supports large and scalable client configuration parameter sets called options.

The following describes the two-phase bootstrap configuration process:

◆ The client contacts the BOOTP server to determine the address and select the boot file name.

◆ The client communicates with the daily File Transfer Protocol (TFTP) server to transfer the file of its boot image.

This section describes the single-phase boot configuration process. In this process, the DHCP Client negotiates with the DHCP server to determine its IP address and obtain detailed information about any other initial configurations required for network operation.

In addition to system restart, The BOOTP protocol client does not use the BOOTP server to re-bind or renew the configuration. The DHCP client does not need to restart the system to use the DHCP server to re-bind or renew the configuration. In addition, the client enters the rebinding status at a fixed interval to use the DHCP server to renew its lease Address allocation. This process is performed in the background and transparent to users.