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Table Of Contents  The TCP/IP Guide
 9  TCP/IP Application Layer Protocols, Services and Applications (OSI Layers 5, 6 and 7)
      9  TCP/IP Network Configuration and Management Protocols (BOOTP, DHCP, SNMP and RMON)
           9  Host Configuration and TCP/IP Host Configuration Protocols (BOOTP and DHCP)
                9  TCP/IP Dynamic Host Configuration Protocol (DHCP)
                     9  DHCP Address Assignment and Dynamic Address Allocation and Management

Previous Topic/Section
DHCP Address Assignment and Allocation Mechanisms
Previous Page
Pages in Current Topic/Section
1
234
Next Page
DHCP Lease "Life Cycle" Overview (Allocation, Reallocation, Renewal, Rebinding and Release) and Lease Timers
Next Topic/Section

DHCP Leases, Lease Length Policies and Management
(Page 1 of 4)

Of the three address allocation methods supported by DHCP, dynamic address allocation is by far the most popular and important. The significance of the change that dynamic addressing represents to how IP addresses are used in TCP/IP can be seen in the semantics of how addresses are treated in DHCP. Where conventionally a host was said to own an IP address, when dynamic address allocation is used, hosts are said instead to lease an address.

The notion of a “lease” conveys very accurately the difference between dynamic allocation and the other types. A host no longer is strictly “entitled” to a particular address, with a server merely telling it what the address is. In DHCP, the server remains the real owner of all the IP addresses in the address pool, and merely gives permission for a client to use the address for a period of time. The server guarantees that it will not try to use the address for another client only during this time. The client is responsible for taking certain actions, as we will see later in this section, if it wants to continue using the address. If it does not successfully reacquire permission for using the address after a period of time, it must stop using it, or risk creating an IP address conflict on the network.

Key Concept: DHCP’s most significant new feature is dynamic allocation, which changes the way that IP addresses are managed. Where in traditional IP each device owns a particular IP address, in DHCP the server owns all the addresses in the address pool, and each client leases an address from the server, usually only for a limited period of time.



Previous Topic/Section
DHCP Address Assignment and Allocation Mechanisms
Previous Page
Pages in Current Topic/Section
1
234
Next Page
DHCP Lease "Life Cycle" Overview (Allocation, Reallocation, Renewal, Rebinding and Release) and Lease Timers
Next Topic/Section

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Version 3.0 - Version Date: September 20, 2005

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