tcpdump

tcpdump

Another popular diagnostic tool is tcpdump. This utility will print, or dump, the TCP packer headers matching the criteria it is given. It has several options you may find useful. Some of the more commonly used options are given here:

• -a: Attempts to convert network addresses to names.

• -c: Ends after receiving the designated number of packets.

• -d: Dumps the compiled packet-matching code in a human readable form to standard output and stops.

• -dd: Dumps packet-matching code as a C program fragment.

• -ddd: Dumps packet-matching code as decimal numbers.

• -F: Uses the designated file as input for the filter expression.

• -i: Listens on a particular interface.

• -n: Don’t convert host addresses to names.

• -p: Don’t put the interface into promiscuous mode.