Configuring a DHCP Server
- 1. Configuring a DHCP Server on Linux Med Taher Ben Abdallah
- 2. What is DHCP 01 Introduction, components, how it works Installing 02 Updating system & installing server Configuration 03 Commands and screenshots Testing 04 Screenshots of usage Table of contents
- 4. The Dynamic Host Configuration Protocol is a network management protocol that assigns an IP address and other information to each host on the network dynamically so that they can interact effectively. DHCP simplifies the job of network administrators by automating and centrally managing IP address assignment, in addition to: ■ Subnet masks ■ Default gateway ■ DNS address ■ Other parameters What is DHCP 4
- 5. Components of DHCP ■ DHCP server Answers IP address requests, provides an available IP address, stores it for the time of the lease and renew it later. It will handle the communication with all the client devices. The server could be a computer or a part of the router. ■ DHCP Client Requests an IP address and communicates with the DHCP server to get it with the rest of the data and confirm the process. ■ DHCP relay agent In charge of communication between the DHCP server and the client. It will listen for messages and pass them to the right place. 5
- 6. How it works 2. DHCP Offer: When the DHCP server receives the DHCP Discovery message it sends a DHCP Offer message to the client containing the proposed IP address, server IP address, client MAC address, subnet mask, default gateway, DNS address, and lease information. DHCP works at the application layer to dynamically assign the IP address to the client through exchanging a series of messages called DHCP transactions or DHCP conversation as follows: 1. DHCP Discovery: The DHCP client broadcast messages to discover the DHCP servers. The client computer sends a packet with the default broadcast destination or the specific subnet broadcast address if any configured. 6
- 7. 4. DHCP ACK: The server then sends Acknowledgment to the client confirming the DHCP lease to the client. The server might send any other configuration that the client may have asked. At this step, the IP configuration is completed and the client can use the new IP settings. How it works 3. DHCP Request: In response to the offer, the client sends a DHCP Request requesting the offered address from one of the DHCP servers. All the other offered IP addresses from remaining DHCP servers are withdrawn and returned to the pool of IP available addresses. 7
- 9. Installing The first step would be to make sure the the device has the last updates necessary through the following command ➔ Then, we go on to install the ISC DHCP server package Now that all is set, let’s move to configuring a DHCP server on the device. 9
- 11. Picking Interface The first step of configuration will be to identify the interface that we will work with, with the command ‘ip a’ or ‘ifconfig’ that lists our available interfaces. 11
- 12. Heading now to the configuration file and introduce the options we want in our server ➔ Our server is the official server for the local network. ➔ The default time for a lease is 600 ms, maximum is 86400 ms. ➔ The Address pool is defined between 192.168.1.150 and 192.168.1.200. ➔ The server will advise to use the address 192.168.1.254 as default gateway. Config file 12
- 13. We need to define the interface that the server should listen to, as it can have many, and we have already picked it. Binding an interface And just before starting up our DHCP server, we might want to check if the firewall is activated or not, in case it is, we should allow the server activities. 13
- 14. Binding an interface Now we’re left with just turning the Server on and checking if it’s functioning by typing the following commands, it should show the message below ➔ The server is up and running ! 14
- 15. Testing 04
- 16. Server testing To test our configured DHCP server, we will need another device to be the client in our case. The client, while on DHCP, has taken an IP address from the address pool: 192.168.1.150, which is the first address in the pool. 16
- 17. Server testing Now moving to the server-side, we can check what devices have obtained their IP address from our server through the ‘dhcp-lease-list’ command as follows. And our system is working well! 17