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This article mainly introduces what protocol bootstrap refers to. It is very detailed and has a certain reference value. Friends who are interested must read it!

The full name of bootstrap protocol is "Bootstrap Protocol", which means "boot protocol" in Chinese. It is a protocol based on "UDP/IP". This protocol is mainly used for clients to obtain their own IP address, server IP address and boot image file name from the server.

The operating environment of this tutorial: Windows7 system, DELL G3 computer

BOOTP: boot Protocol (Bootstrap Protocol)

Boot Protocol (BOOTP) is a UDP/IP-based protocol. This protocol allows the starting host to be dynamically configured without user supervision. BOOTP is mainly used for clients to obtain their own IP address, server IP address and boot image file name from the server. Other configuration information, such as the local subnet mask, local time offset, default router address, and various Internet server addresses, can communicate with clients using the BOOTP protocol.

BOOTP uses two different well-known communication ports, UDP67/68. UDP67 is for the server and UDP68 is for the BOOTP client. When the client starts up without an IP address itself, the BOOTP client issues a broadcast IP address query request packet called BOOTREQUEST, which contains the client's physical address and possibly an IP address, if one already exists. The customer uses the address 255.255.255.255 to send a broadcast, which is called a limited broadcast address. The client then waits for a response from the server, and if it does not receive a response within a certain period of time, the client reissues the request.

By booting the reply (bootreply) packet, the server responds to client requests. The request can contain a "generic" boot file name, such as unix or ethertip. However, when the server sends a boot reply packet, it replaces this field with the exact path name of the corresponding boot file. To determine the pathname, the server queries its own database. This database is associated with the client address, the request file name, and a special boot file customized for the user. If the request (bootrequest) file name is empty, the server returns a file name field that represents the default file to be loaded by the guest machine.

If the client IP address is not known, the server must have a database corresponding to the hardware address and the IP address. The client IP address is also placed in a field of "bootreply".

BOOTP is similar to RARP, but RARP only runs at the data link layer of the LAN network, while the UDP/IP-based configuration protocol BOOTP provides more configuration information, which allows the entire IP network to be configured dynamically. In short, BOOTP and its extensions become the foundation of dynamic Host configuration Protocol (DHCP).

Protocol structure

8162432OpHtypeHlenHopsXidSecsFlagsCiaddrYiaddrSiaddrGiaddrChaddr (16 bytes) sname (64 bytes) File (128 bytes) Option (variable)

Op-message operation code, either a bootstrap request (BOOTREQUEST) or a bootstrap reply (BOOTREPLY)

Htype-hardware address typ

Hlen-hardware address length

Xid-transaction ID.

Secs-time spent by the client after starting an address request or renewal (in seconds)

Flags-Marker

Ciaddr-client IP address

Yiaddr-"your" (client) IP address

Siaddr-IP address of the next server available in bootstrap

Giaddr-IP address of the agent when starting through the agent

Chaddr-client hardware address

Sname-other available server host names, null Terminator

File-boot file name, null Terminator; generic name or null value in DHCPDISCOVER package, fully qualified directory pathname in DHCPOFFER package

Options-optional parameter number field

BOOTP is defined by IETF (http://www.ietf.org) RFC 951 and RFC 1542

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