Which destination IPv4 address does a DHCPv4 client use to send the initial DHCP Discover packet when searching for a server?

Which destination IPv4 address does a DHCPv4 client use to send the initial DHCP Discover packet when searching for a server?

• A. 255.255.255.0
• B. 0.0.0.0
• C. 255.255.255.255
• D. 239.255.255.255

Answer: (C)

The key idea is that a DHCP Discover is sent before the client has an IP address, so it must be delivered to every potential DHCP server on the local network. To achieve that, the client uses the limited broadcast address: 255.255.255.255. This ensures all devices on the broadcast domain can receive the Discover message, and any DHCP server can respond with an offer. The message is carried in a UDP/BOOTP-DHCP frame, with the client not yet having an IP, which is why unicast to a specific server isn’t possible at this stage. Other addresses don’t fit this scenario: 0.0.0.0 is typically used as the source IP when none is assigned, not as the destination; 255.255.255.0 is a subnet-wide broadcast that depends on the subnet mask and isn’t universally applicable; 239.255.255.255 is a multicast address, which DHCP Discover does not use.

The key idea is that a DHCP Discover is sent before the client has an IP address, so it must be delivered to every potential DHCP server on the local network. To achieve that, the client uses the limited broadcast address: 255.255.255.255. This ensures all devices on the broadcast domain can receive the Discover message, and any DHCP server can respond with an offer. The message is carried in a UDP/BOOTP-DHCP frame, with the client not yet having an IP, which is why unicast to a specific server isn’t possible at this stage.

Other addresses don’t fit this scenario: 0.0.0.0 is typically used as the source IP when none is assigned, not as the destination; 255.255.255.0 is a subnet-wide broadcast that depends on the subnet mask and isn’t universally applicable; 239.255.255.255 is a multicast address, which DHCP Discover does not use.