11 Dynamic Host configuration protocol (DHCP)

1. Front: What problem does DHCP solve in modern networks?

Back: Manually configuring IP addresses, subnet masks, gateways, and DNS servers for thousands of devices is impractical. DHCP automates this process.

2. Front: What does the acronym DORA stand for in the context of DHCP?

Back: The four-step process a client uses to get an IP address: Discover, Offer, Request, Acknowledgement.

3. Front: In the DHCP Discover step, what source IP address and destination IP address does the client use, and why?

Back: Source: 0.0.0.0 (because it has no IP). Destination: 255.255.255.255 (broadcast). It does this to find any available DHCP servers on the network.

4. Front: What is the purpose of the DHCP Offer message sent by the server?

Back: It is a response to the Discover message, proposing an IP address and other configuration parameters to the client.

5. Front: Why does the client send a DHCP Request as a broadcast instead of directly to the server that made the offer?

Back: To inform all DHCP servers which offer it has accepted. This tells other servers they can withdraw their offers and free up those IP addresses.

6. Front: What is the final step that officially assigns the IP address to the client and prevents it from being given to another device?

Back: The DHCP Acknowledgement (ACK) message from the server.

7. Front: What is a DHCP Scope?

Back: A predefined range of IP addresses and configuration settings (like subnet mask, gateway, DNS) that a DHCP server can assign to clients.

8. Front: What are DHCP exclusions within a scope?

Back: Specific IP addresses within the scope's range that the server is not allowed to assign dynamically. These are often reserved for devices with static IPs, like routers or printers.

9. Front: What is a DHCP Reservation (or Static DHCP Assignment)?

Back: It ensures a specific device always receives the same IP address from the DHCP server by linking the reservation to the device's MAC address.

10. Front: What is the main administrative advantage of using a DHCP reservation instead of manually configuring a static IP on a device like a server?

Back: All IP management is centralized on the DHCP server. If the network's IP scheme changes, you only update the DHCP server, not every individual device.

11. Front: What UDP port does a DHCP client use, and what UDP port does a DHCP server use?

Back: Client: UDP port 68. Server: UDP port 67.

12. Front: Besides an IP address and subnet mask, what are two other common configuration options a DHCP server can provide to a client?

Back: Default Gateway (Router) address and DNS Server addresses.