DHCP extends the vendor specific area in BOOTP to 312 bytes from 64.
DHCP RFCs are 1533, 1534, 1541, and 1542.
To be clear on this, I quote RFC 1531 which states "DHCP messages from a client to a server are sent to the 'DHCP server' port (67), and DHCP messages from a server to a client are sent to the 'DHCP client' port (68)"
DHCP's purpose is to enable individual computers on an IP network to extract their configurations from a server (the 'DHCP server') or servers, in particular, servers that have no exact information about the individual computers until they request the information.
DHCP is generally aimed at giving "easy moves" capability to networks that are divided into subnets on a geographical basis, or on separate networks.
DHCP servers and relay agents use their knowledge of what LAN the client-station is on to select the subnet number for the client-station's new IP address whereas such switches use the subnet number sent by the client-station to decide which (virtual) LAN to put the station on.
DHCP (Dynamic Host Configuration Protocol) is a communications protocol that lets network administrators centrally manage and automate the assignment of Internet Protocol (IP) addresses in an organization's network.
DHCP lets a network administrator supervise and distribute IP addresses from a central point and automatically sends a new IP address when a computer is plugged into a different place in the network.
DHCP uses the concept of a "lease" or amount of time that a given IP address will be valid for a computer.
RFC 2131 (rfc2131) - Dynamic Host Configuration Protocol(Site not responding. Last check: 2007-11-06)
DHCP clarifies the interpretation of the 'siaddr' field as the address of the server to use in the next step of the client's bootstrap process.
DHCP messages from a client to a server are sent to the 'DHCP server' port (67), and DHCP messages from a server to a client are sent to the 'DHCP client' port (68).
The DHCP specification describes only the interactions between clients and servers when the clients and servers choose to interact; it is beyond the scope of the DHCP specification to describe all of the administrative controls that system administrators might want to use.
DHCP consists of two components: a protocol for delivering host-specific configuration parameters from a DHCP server to a host and a mechanism for allocation of network addresses to hosts.
DHCP is built on a client-server model, where designated DHCP server hosts allocate network addresses and deliver configuration parameters to dynamically configured hosts.
DHCP must allow local system administrators control over configuration parameters where desired; e.g., local system administrators should be able to enforce local policies concerning allocation and access to local resources where desired.
www.ietf.org /rfc/rfc2131.txt (11923 words)
DHCP, Dynamic Host Configuration Protocol(Site not responding. Last check: 2007-11-06)
First, DHCP defines mechanisms through which clients can be assigned a network address for a finite lease, allowing for serial reassignment of network addresses to different clients.
DHCP introduces a small change in terminology intended to clarify the meaning of one of the fields.
DHCP is designed to use the same relay agent behavior as has been specified for the BOOTPprotocol.
DHCP, the Dynamic Host Configuration Protocol, describes the means by which a system can connect to a network and obtain the necessary information for communication upon that network.
DHCP client support is provided within both the installer and the base system, obviating the need for detailed knowledge of network configurations on any network that runs a DHCP server.
The DHCP client keeps a database of valid leases in this file, which is written as a log.
Note: a DHCP relay agent is the same thing as a BOOTP relay agent, and the latter phrase is more commonly used.
Such a computer doesn't have the IEEE-style MAC address that DHCP requires to act as its key to determining which client-computer is which within the same subnet.
DHCP requires disk storage (or some other form of reliable non-volatile storage), making the task of DHCP service compatible with servers but incompatible with dedicated routers.
If there are multiple Microsoft Dynamic Host Configuration Protocol (DHCP) servers in a multinetted environment, more than one DHCP server may have a lease for a given client.
In this case, client leases are being held on both DHCP servers, although the client is using only one lease.
To prevent the problem, configure each DHCP server in a multinetted environment with a scope within the range of each subnet that is being used for DHCP clients.
Later versions of the DHCP Server service, such as those that are provided as part of Windows 2000 Server or Windows Server 2003 are not vulnerable to this issue.
DHCP does this by using a server computer to centrally manage IP addresses and other related configuration details used on your network.
Windows NT 4.0 Server provides the DHCP Server service, which enables the server computer to perform as a DHCP Server and to provide configuration settings to DHCP-enabled client computers on your network as described in the DHCP IETF RFC 2131.
The DHCP server, client and relay agent are provided both as reference implementations of the protocol and as working, fully-featured sample implementations.
Ted Lemon's paper on the ISC DHCP Distribution for the June, 1998 Freenix track of the Usenix conference.
If you are using one of these versions of the ISC DHCP server, we strongly urge you to ugprade.
The DHCP server can be on an NT machine, or it can be on your Linux machine.
Note that if your Windows machine previously received an IP from your Linux dhcp, and then your dhcpd.leases was erased and recreated, it might not write that info into it until the lease "expires" and then logs in again.
DHCP can do a lot more than just give the client an IP address.
dhcp.org - Resources for DHCP(Site not responding. Last check: 2007-11-06)
The Dynamic Host Configuration Protocol (DHCP) is an Internet protocol for automating the configuration of computers that use TCP/IP.
DHCP can be used to automatically assign IP addresses, to deliver TCP/IP stack configuration parameters such as the subnet mask and default router, and to provide other configuration information such as the addresses for printer, time and news servers.
DHCP also supports a mix of static and dynamic IP addresses.
INS: Secure DHCP Management - Centralize and automate DHCP with next-generation IP management technology.
Brief overview of how DHCP works with links to related articles.
www.webopedia.com /TERM/D/DHCP.html (282 words)
The DHCP Handbook(Site not responding. Last check: 2007-11-06)
From the author of the DHCP RFCs and the author of the ISC DHCP server, a complete introduction and reference to the Dynamic Host Configuration Protocol...
The DHCP Handbook is a complete resource for understanding DHCP, designing and deploying DHCP services and debugging problems with DHCP clients and servers.
Regardless of the DHCP service you use, this book is an absolute must for network administrators deploying and managing DHCP services.
In some systems, the device's IP address can even change while it is still connected.
Dynamic addressing simplifies network administration because the software keeps track of IP addresses rather than requiring an administrator to manage the task.
Describes the IETF Dynamic Host Configuration working group and includes contact and mailing list information and links to Internet drafts and Request for Comments documents.
