To print all packets arriving at or departing from sundown:
tcpdump host sundown
To print traffic between helios and either hot or ace:
tcpdump host helios and \( hot or ace \)
To print all IP packets between ace and any host except helios:
tcpdump ip host ace and not helios
To print all traffic between local hosts and hosts at Berkeley:
tcpdump net ucb-ether
To print all ftp traffic through internet gateway snup: (note
that the expression is quoted to prevent the shell from
(mis-)interpreting the parentheses):
tcpdump 'gateway snup and (port ftp or ftp-data)'
To print traffic neither sourced from nor destined for local
hosts (if you gateway to one other net, this stuff should never
make it onto your local net).
tcpdump ip and not net localnet
To print the start and end packets (the SYN and FIN packets) of
each TCP conversation that involves a non-local host.
tcpdump 'tcp[tcpflags] & (tcp-syn|tcp-fin) != 0 and not src and dst net localnet'
To print the TCP packets with flags RST and ACK both set. (i.e.
select only the RST and ACK flags in the flags field, and if the
result is "RST and ACK both set", match)
tcpdump 'tcp[tcpflags] & (tcp-rst|tcp-ack) == (tcp-rst|tcp-ack)'
To print all IPv4 HTTP packets to and from port 80, i.e. print
only packets that contain data, not, for example, SYN and FIN
packets and ACK-only packets. (IPv6 is left as an exercise for
the reader.)
tcpdump 'tcp port 80 and (((ip[2:2] - ((ip[0]&0xf)<<2)) - ((tcp[12]&0xf0)>>2)) != 0)'
To print IP packets longer than 576 bytes sent through gateway
snup:
tcpdump 'gateway snup and ip[2:2] > 576'
To print IP broadcast or multicast packets that were not sent via
Ethernet broadcast or multicast:
tcpdump 'ether[0] & 1 = 0 and ip[16] >= 224'
To print all ICMP packets that are not echo requests/replies
(i.e., not ping packets):
tcpdump 'icmp[icmptype] != icmp-echo and icmp[icmptype] != icmp-echoreply'
