tcpdump refresher

Kostis Netzwerkberatung
Konstantinos Kostis
Talstr. 25, D-63322 Rödermark
Tel. +49 6074 881056, FAX 881058,

You may use this information free of charge at your own risk


tcpdump everything between two hosts

tcpdump -e -f -l -n -S -vv -x host ipaddr1 and host ipaddr2

option function/meaning
-e Print the link-level header on each dump line.
-f Print `foreign' internet addresses numerically rather than symbolically (this option is intended to get around serious brain damage in Sun's yp server -- usually it hangs forever translating non-local internet numbers).
-l Make stdout line buffered. Useful if you want to see the data while capturing it. E.g., ``tcpdump -l | tee dat'' or ``tcpdump -l > dat & tail -f dat''.
-n Don't convert addresses (i.e., host addresses, port numbers, etc.) to names.
-S Print absolute, rather than relative, TCP sequence numbers.
-vv Even more verbose output. For example, additional fields are printed from NFS reply packets.
-x Print each packet (minus its link level header) in hex. The smaller of the entire packet or snaplen bytes will be printed.

If you are only interested in certain ports to be looked at, add port portnum