Please Whitelist This Site?

I know everyone hates ads. But please understand that I am providing premium content for free that takes hundreds of hours of time to research and write. I don't want to go to a pay-only model like some sites, but when more and more people block ads, I end up working for free. And I have a family to support, just like you. :)

If you like The TCP/IP Guide, please consider the download version. It's priced very economically and you can read all of it in a convenient format without ads.

If you want to use this site for free, I'd be grateful if you could add the site to the whitelist for Adblock. To do so, just open the Adblock menu and select "Disable on tcpipguide.com". Or go to the Tools menu and select "Adblock Plus Preferences...". Then click "Add Filter..." at the bottom, and add this string: "@@||tcpipguide.com^$document". Then just click OK.

Thanks for your understanding!

Sincerely, Charles Kozierok
Author and Publisher, The TCP/IP Guide


NOTE: Using software to mass-download the site degrades the server and is prohibited.
If you want to read The TCP/IP Guide offline, please consider licensing it. Thank you.

The Book is Here... and Now On Sale!

Read offline with no ads or diagram watermarks!
The TCP/IP Guide

Custom Search







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 Dynamic Address Allocation and Management
Previous Page
Pages in Current Topic/Section
1
234
Next Page
DHCP Leases, Lease Length Policies and Management
Next Topic/Section

DHCP Address Assignment and Allocation Mechanisms
(Page 1 of 4)

The two main functions of the Dynamic Host Configuration Protocol are to provide a mechanism for assigning addresses to hosts, and a method by which clients can request addresses and other configuration data from servers. Both functions are based on the ones implemented in DHCP's predecessor, BOOTP, but the changes are much more significant in the area of address assignment than they are in communication. It makes sense to start our look at DHCP here, since this will naturally lead us into a detailed discussion of defining characteristic of DHCP: dynamic addressing.

DHCP Address Allocation Mechanisms

Providing an IP address to a client is the most fundamental configuration task performed by a host configuration protocol. To provide flexibility for configuring addresses on different types of clients, the DHCP standard includes three different address allocation mechanisms:

  • Manual Allocation: A particular IP address is pre-allocated to a single device by an administrator. DHCP only communicates the IP address to the device.

  • Automatic Allocation: DHCP automatically assigns an IP address permanently to a device, selecting it from a pool of available addresses.

  • Dynamic Allocation: DHCP assigns an IP address from a pool of addresses for a limited period of time chosen by the server, or until the client tells the DHCP server that it no longer needs the address.

I don't really care for the names “automatic” and “dynamic” allocation, because they don't do a good job of clearly conveying the differences between these methods. Both can be considered “automatic” because in each the DHCP server assigns an address with no administrator intervention required. The real difference between them is only in how long the IP address is retained, and therefore, whether a host's address varies over time. I think better names would be “static/permanent automatic allocation” and “dynamic/temporary automatic allocation”. But then, nobody really cares much what I think. J

Regardless of what you call them, all three of these methods exist for configuring IP hosts using DHCP. It is not necessary for an administrator to choose one over the others. Instead, he or she will normally combine the methods, using each for the devices where it makes the most sense.


Previous Topic/Section
DHCP Address Assignment and Dynamic Address Allocation and Management
Previous Page
Pages in Current Topic/Section
1
234
Next Page
DHCP Leases, Lease Length Policies and Management
Next Topic/Section

If you find The TCP/IP Guide useful, please consider making a small Paypal donation to help the site, using one of the buttons below. You can also donate a custom amount using the far right button (not less than $1 please, or PayPal gets most/all of your money!) In lieu of a larger donation, you may wish to consider purchasing a download license of The TCP/IP Guide. Thanks for your support!
Donate $2
Donate $5
Donate $10
Donate $20
Donate $30
Donate: $



Home - Table Of Contents - Contact Us

The TCP/IP Guide (http://www.TCPIPGuide.com)
Version 3.0 - Version Date: September 20, 2005

Copyright 2001-2005 Charles M. Kozierok. All Rights Reserved.
Not responsible for any loss resulting from the use of this site.