Installation instructions for iftop $Id: INSTALL,v 1.4 2014/01/19 20:11:39 pdw Exp $ iftop is now autoconf/automake-enabled. You should be able to build it on common platforms by typing `./configure && make'. There is one gotcha, however, which is that some systems, such as FreeBSD, lack a working implementation of the gethostbyaddr_r(3) C library function. On such systems, you may want to use the --with-resolver=ares configure option to build a version of iftop which uses the ARES asynchronous DNS library for name resolution. An alternative is to use --with-resolver=netdb_1thread, which will make iftop run only one name resolution thread. This is not recommended.