Which port number is used by the DHCP server in IPv4 networks?

Which port number is used by the DHCP server in IPv4 networks?

• A. 68
• B. 13
• C. 67
• D. 9

Answer: (C)

DHCP uses UDP with fixed port numbers: the server listens on port 67, while the client uses port 68. In IPv4, the typical exchange starts with the client broadcasting a DHCPDISCOVER from source port 68 to destination port 67. The server responds from port 67 to the client’s port 68, then the process continues with DHCPOFFER, DHCPREQUEST, and DHCPACK. So the port used by the DHCP server is 67. Port 68 is the client’s port, not the server’s. Ports 13 and 9 are not used for DHCP in IPv4.

DHCP uses UDP with fixed port numbers: the server listens on port 67, while the client uses port 68. In IPv4, the typical exchange starts with the client broadcasting a DHCPDISCOVER from source port 68 to destination port 67. The server responds from port 67 to the client’s port 68, then the process continues with DHCPOFFER, DHCPREQUEST, and DHCPACK. So the port used by the DHCP server is 67. Port 68 is the client’s port, not the server’s. Ports 13 and 9 are not used for DHCP in IPv4.