DHCP

DHCP, or Dynamic Host Configuration Protocol, is an internet standard defined by RFC1541 and later by RFC2131(as well as a few other RFCs relevant to other physical mediums) as an extension to BOOTP.

DHCP is a fairly elegant method to give client computers configuration information to allow them access to an IP network.

Conceptually the protocol is straight forward:

  • A client machine boots and activates it’s network adapter
  • A client machine requests IP configuration information
  • A server provides IP configuration information with a time specific lease
  • A client consumes the IP configuration information and setups up it’s network adapter
  • A client attempts to renew it’s IP configuration information when the lease has half expired
  • A client releases it’s IP configuration information when done with it
  • A server release client specific configuration information either when it’s been released by the client or the lease has expired.

Most home and small businesses use DHCP and they use their router / gateway device as the DHCP server (most of these devices default to enabling their DHCP server).

Some gateways allow you a great deal of control over the DHCP server, they allow you to set MAC address to IP bindings, specify the DHCP records to be provided.  Some gateways only allow you to turn on or off the service.

An option to running the DHCP server in your router / gateway would be to run it on a machine that is always on (or at least is one when any machine that might need DHCP services might be on).

Microsoft provides a DHCP server as part of their server operating systems (Server 2003 and Server 2008), ISC provides a DHCP server that can be run on a variety of operating systems, and there are a few shareware and open source DHCP servers that might fit your needs.

There’s no question that DHCP is the way to manage IP configuration information in a small network, and most business and enterprises use DHCP as well.

Alternately if you don’t have a device that does DHCP and don’t want to or can’t use a software solution you can use the “Alternate Configuration” panel on a Windows PC to setup the IP address configuration information and if a DHCP server is ever present it will override the information you’ve entered on the PC.  This is very handy for laptops that need to be configured by DHCP when they’re out and about or at the office, but when you don’t have a DHCP server at home and need to connect to another machine.  This is different than statically setting the IP address on the machine, if you do that you have to change the configuration each time you need DHCP.

Originally posted 2009-01-11 12:39:33.