Which three statements describe a DHCP Discover message? (Choose three.)
a. The source MAC address is 48 ones (FF-FF-FF-FF-FF-FF).
b. The destination IP address is 255.255.255.255.
c. The message comes from a server offering an IP address.
d. The message comes from a client seeking an IP address.
e. All hosts receive the message, but only a DHCP server replies.
f. Only the DHCP server receives the message.
The Correct Answer and Explanation is:
The correct answers are:
b. The destination IP address is 255.255.255.255.
d. The message comes from a client seeking an IP address.
e. All hosts receive the message, but only a DHCP server replies.
Explanation (300+ words):
Dynamic Host Configuration Protocol (DHCP) is an essential networking protocol that enables devices (clients) to automatically obtain IP configuration information from a DHCP server. One of the initial steps in the DHCP process is the DHCP Discover message.
1. DHCP Discover Originates from a Client: (Option d – Correct)
The DHCP Discover message is initiated by a client device that has just joined a network and does not yet have an IP address. This message is sent as a broadcast to locate available DHCP servers that can provide IP addressing and other configuration details.
2. Broadcast Message to 255.255.255.255: (Option b – Correct)
Since the client does not yet have an IP address or know the IP address of any DHCP server, the message is sent to the broadcast IP address 255.255.255.255. This allows all devices on the local subnet to receive the message.
3. All Hosts Receive It, But Only DHCP Server Replies: (Option e – Correct)
Being a broadcast, the Discover message reaches all hosts on the local network. However, only devices configured to act as DHCP servers will recognize and respond to it by sending a DHCP Offer. Other devices ignore it.
Incorrect Options:
a. The source MAC address is 48 ones (FF-FF-FF-FF-FF-FF) – Incorrect
This describes the destination MAC address in Ethernet broadcasting, not the source. The source MAC is the actual hardware address of the client.
c. The message comes from a server offering an IP address – Incorrect
This describes a DHCP Offer message, not a Discover message. A Discover message is sent by the client, not the server.
f. Only the DHCP server receives the message – Incorrect
The message is broadcasted, so all hosts on the subnet receive it. However, only DHCP servers process and respond.
Conclusion:
A DHCP Discover message is the first step in obtaining a dynamic IP address. It is sent by a client as a broadcast, received by all local devices, but only DHCP servers respond.