68
DHCP client port — receives IP configuration from server
Dynamic Host Configuration Protocol – Client
What is port 68?
UDP port 68 is used by the DHCP client to receive IP configuration (address, subnet mask, gateway, DNS) from a DHCP server listening on port 67. Every time a device (PC, phone, printer) connects to a network, this port is involved in the automatic address assignment process. It is a fundamental part of any LAN's operation and is not normally exposed beyond the local network segment.
Quick checks
$
nc -zv example.com 68
$
nmap -p 68 example.com