How to use TCPDump

• http://www.cyberciti.biz/faq/linux-monitor-all-network-traffic-except-ssh-port-22

DHCP debugging with tcpdump

tcpdump filter to match DHCP packets including a specific Client MAC Address:

tcpdump -i br0 -vvv -s 1500 '((port 67 or port 68) and (udp[38:4] = 0x3e0ccf08))'

tcpdump filter to capture packets sent by the client (DISCOVER, REQUEST, INFORM):

tcpdump -i br0 -vvv -s 1500 '((port 67 or port 68) and (udp[8:1] = 0x1))'