What is a DHCP?


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Dynamic Host Configuration Protocol supports automated access to IP address and additional options required for TCP/IP net operations. Protocol works in client-server system contacting to DHCP server and receiving necessaries settings.

Avoiding manual tuning control and reducing errors amount, network manager assigns codes range distributed by server.

Distribution methods of IP addresses

DHCP protocol implements three distribution methods:

  1. Manual mode allows storing address info on a DHCP server permitting simple configuration method if needed.
  2. Automatic distribution assigns unattached random IP locations from range specified by administrator.
  3. Dynamic mode is analogous to automatic distribution but issues addresses on a designate period. Once this time expires, client orders new number and declines if desired.

DHCP options

Options are represented by variable-length strings composed of octets. The first octet identifies option code, the second one points to the number of following octets and others depend on option code.

Example of the Protocol options:

“DHCP Message Type” option dispatching the message “Offer” looks like 0x35,0x01,0x02. It follows that 0x35 is an option code, 0x01 signifies one following octet, and 0x02 is a message interpretation.

The most extended and frequently used options are:

  • default router IP address;
  • DNS servers’ addresses;
  • subnet mask;
  • DNS domain name;
  • ISP identification.

DHCP system weaknesses

Dispensing network administrators from multiple routine operations, DHCP leaves number of challenges open which will arise in a real network environment sooner or later. Constant IP reversion seems unpractical to some network devices, such as communal printer required to fix static address. This is a case of special programs granting continuous remote access to the device and attaching to define IP. But these problems are tackled and do not harm by contrast with noted below.

To begin with, the protocol maintains miniscule information security level. Protection mechanisms do not prevent illegal DHCP servers’ creation delivered mistaken or explosive information, such as wrong or enabled IP addresses, false information about routing technique etc.  At the other extreme clients created with malign purposes import configuration concepts intended to legal net computers and steal notable part of available resources.

On top of that, DHCP is incapable being fault-tolerant and deficient in active-notification mechanism about extreme conditions (e.g. major deficiencies in addresses) or timely server confirmation about address emancipation.

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