Running DHCP or proxyDHCP with coreos/dnsmasq on a host requires that the Firewall allow DHCP and TFTP (for chainloading) services to run.

Port collision

Running DHCP or proxyDHCP can cause port already in use collisions depending on what's running. Fedora runs bootp listening on udp/67 for example. Find the service using the port.

$ sudo lsof -i :67

Evaluate whether you can configure the existing service or whether you'd like to stop it and test with coreos/dnsmasq.

No boot filename received

PXE client firmware did not receive a DHCP Offer with PXE-Options after several attempts. If you're using the coreos/dnsmasq image with -d, each request should log to stdout. Using the wrong -i interface is the most common reason DHCP requests are not received. Otherwise, wireshark can be useful for investigating.