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Iftop

This generates curses bar graphs showing bandwidth per host or per connection. That is, it can group all bandwidth per host, or group by individual connections. The view is updated quickly, but also includes a weighted average, so this balances spikes with trends. The top two connections over the last 10 seconds always appear at the top. Bandwidth numbers are shown for the last 2,10, and 40 seconds. Iftop supports libpcap-style filters, so you can look at just certain types of traffic.

• To show bandwidth broken down by individual connections with port numbers (more like pktstat):

iftop -i eth0 -p -P -n -N

• To show bandwidth grouped by host:

iftop -i eth0 -p -n -N

• You can add libpcap-style filters if you want to look at only some connections. Here we want to see all connections to 192.168.1.16 (a mail server), but we don't want to see the traffic between 192.168.1.14 (an iSCSCI storage server) and the mail server:

iftop -i eth0 -p -P -n -N -f "net 192.168.1.16 and not net 192.168.1.14"

• This shows all HTTP traffic:

iftop -i eth0 -p -P -n -N -f "port 80"

• You can also add or change a filter while iftop is running by pressing the f key.