Explore the DHCP lease-generation process using DORA.
- [Instructor] So let's talk about the actual DHCP Lease Generation process. It is a four-step process, commonly known as DORA. So if you've ever heard anybody just generally talking about a DORA process, they're talking about DHCP Lease Generation. So what do we mean by DORA? Well, first of all, the letters are D, O, R, A, and each letter represents one of the four steps in the process.
So let's talk about step one. Step one is D, and that stands for discover. What happens is that a client who needs an IP address, and it's been configured to get it automatically from a DHCP server, it needs to discover the presence of any DHCP servers on the network. So it will do a broadcast, the net broadcast package, by the way, is actually called a DHCP Discover. If you ever sniff your packets out on the network, and you see DHCP Discover, that's where this comes from.
But what the client is basically doing is, it's just broadcasting out, hey, I'm a client, and I need an IP address. Is there any DHCP server out there that can help me? So that's the discover process. Then from there, we go in to step two, which is, any DHCP servers on the network which hear that broadcast, they will go ahead and make an offer back to the client.
So that's the O in step two, it's for offer. And any and all DHCP servers that hear that original discover, are kind of yelling back to the client saying, yes, I am here, I'm a DHCP server. And I have an IP address for you. Here it is if you want it. So it makes an offer. Then the client, in step three, will make a request. And that's what the R stands for. So the client will request back to the DHCP server and say, yes, I would indeed like that IP address.
That is the one I'm going to take. And it'll do that to whatever is the first DHCP server it hears back from if there happens to be more than one. It'll send that request back to the DHCP server and then the final step is A for acknowledge. Some people say acknowledgement, and the reality is that the actual packet on the network is called a DHCP ACK. So just A-C-K. And that is the DHCP server responding back to the client with an acknowledgment saying, okay, it's yours, it's been logged in my database, and you have it for x amount of time, whatever the least duration is.
So just as a quick review, the four-step process is, a client first discovers the presence by saying, hey, I'm looking for a DHCP server. Then DHCP server responds back with an offer saying, I'm here, here's an IP address. Then from there, the client says, thank you, I would like that IP address, that's my request. And step four is the server responding back with an acknowledgment saying, okay, you got it, it's been logged, and here's how long you can have it. That is the DHCP Lease Generation process.
- What is Dynamic Host Configuration Protocol (DHCP)?
- Setting up DHCP
- Securing and troubleshooting DHCP
- Configuring a DHCP relay agent
- Deploying Domain Name System (DNS)
- Creating stub zones and reverse lookup zones
- Testing queries
- DNS security