DHCP basics: Understanding the Dynamic Host Configuration Protocol

What is DHCP, and why is this technology important? Look at our guide, and any confusion over the DCHP basics you've been feeling can be put to rest.

DHCP (Dynamic Host Configuration Protocol), an extension of an earlier network IP management protocol, is a technology...

that "leases" the amount of time that a given IP address will be valid for a computer. If you are unsure of how to make this technology improve your IP address management system, let our tutorial be your guide on everything you need to know about DHCP -- including how DHCP works, how to keep DHCP secure, what DHCP means for VoIP and how to troubleshoot DHCP.

What is DHCP?

What exactly is DHCP? This technology 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 allows network administrators to monitor and distribute IP addresses from a central point and automatically send a new IP address when a computer is plugged in somewhere else in the network.

Read the full definition of Dynamic Host Configuration Protocol.

How does DHCP work?

More on the details of DHCP

DHCP lease renewal on IP phones

Do I have to disable DHCP on my router to create a DHCP server?

The DHCP, a network management protocol, is typically used for assigning dynamic IP addresses to network clients. The main advantage of using this technology is to be able to take a finite amount of IP address space and dividing them up and distributing them to transient users as needed, reclaiming addresses no longer in use. The use of DHCP also saves end users and desktop administrators from manually assigning IP addresses to systems. In order to configure DHCP, the administrator must set a value called the DHCP lease. This is the amount of time a system is allowed to occupy an IP address without contacting the DHCP server. When the time runs out, the system must request a renewal of the lease from the server. DHCP leases are measured in days on stable networks where the same systems are usually present from day to day. Networks with many transient users (such as public areas) typically have short lease times, allowing an efficient reuse of addresses.

Keep reading about how DHCP works.

How to set up DHCP for VoIP

DHCP and Trivial File Transfer Protocol (TFTP) must interact in VoIP environments because IP phones typically get their IP address dynamically from a DHCP server. Because the phones usually aren't on the same subnet as the TFTP server, the phones will learn the IP address of the TFTP server from the DHCP server. They get this information in the form of a DHCP "Option" -- specifically, Option 150. Many servers -- for instance, Windows Server 2003, 2008 (both versions) and 2012-- now include Option 150. If you don't use these servers, you can configure your servers for voice.

Learn how to make your servers VoIP friendly.

How to secure DHCP

Rogue DHCP server malware is a new twist on an old concept. DHCP has been plagued with security concerns from the start, but effective threat mitigation strategies exist. The bad news is that many organizations haven't bothered to deploy them.

See how to thwart rogue DHCP server malware attacks.

How to troubleshoot a DHCP server

One very common DHCP-related issue is the assignment of an unexpected IP address. Solutions to this problem and other issues, such as failure to lease IP addresses, are addressed in this tip below.

Tackle common DHCP server problems.

Do you have more questions about DHCP basics? Then email your question to [email protected] to have them answered by an expert.

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