While reviewing the SysLog messages on my Linux Debian (v8 Jessie) server I noticed that the following error is flooding my logs:
dhclient.c:2243: Failed to send 300 byte long packet over fallback interface.
send_packet: Operation not permitted
After investigation it turned out that my local firewall was a bit to restrictive dropping outgoing DHCP packets.
The solution is simple, just add the following statement to your iptables:
iptables -A OUTPUT -p udp -o eth0 --dport 67 --sport 1024:65535 -j ACCEPT