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On my FreeBSD box, working as my LAN's router, I tried using iftop (from ports/net-mgmt) to monitor bandwidth usage. The program works well for monitoring the server's LAN interface-card, but not for the tun0 virtual/loopback interface created by ppp. It does show connected internet-hosts, but no traffic is shown (upload and download rates all show 0 b/s). The host-list is refreshed with new hosts (though a bit slowly), but other than that nothing happens. top shows WCPU-usage > 100% for iftop. Pressing Q or Ctrl-C for quitting takes forever (>10 secs).

What causes this, and are there any solutions to get iftop to work for my tun0 interface?

I'm open towards other programs (preferably a program included in the FreeBSD ports-collection), but would like a terminal-program (ncurses or something) that resembles iftop by representing outgoing+incoming traffic for each connected host as ASCII-graphs. Any suggestions for such programs?

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up vote 0 down vote accepted

I don't have any solution to my iftop issue, but I found some useful alternatives that does almost the same (although none with per-host usage-graphs). While it seems iftop has to be monitoring the tun0 interface (otherwise it won't show any connected hosts), some of the others (pktstat, for instance) should be set up to monitor the underlying physical WAN-interface (em1 in my case).

Alternatives include (but are almost certainly not limited to) these programs, all in the FreeBSD ports collection, and all run in the terminal:

  • pktstat (I find these args useful: pktstat -P -t -n -B -i em1)
  • bmon (shows usage graph for each interface over time)
  • trafshow
  • bwm-ng

I found these from this site, where there are screenshots of each program.

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