dhcpdoctor sends DHCP requests and checks if it gets an offer from DHCP server.
It supports BOOTP+DHCP for IPv4 and DHCPv6 for IPv6.

It can operate as a DHCP client by sending requests on the local network via
broadcast/multicast or as a DHCP client and relay in one tool by unicasting
requests to the specified IP address.

Program output and exit codes are Nagios/Icinga compatible. Response time
from DHCP server is measured and returned as performance data.