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I have a weird problem with traffic here. My server is connected via 100mbit to a netgear switch. Now sometimes when I look at the traffic on the server using iptraf it reports in excess of 16000kbytes/s, that is 16 MB/s on a 100mbit line. Clearly this can't be right, also the netgear switch can measure and display traffic, and it is reporting much lower traffic volumes, somewhere around 100kbytes/s.

After I noticed this I installed nethogs to see which process is sucking up all that bandwidth, but just like the switch, it showed almost no utilization at all. Can anybody explain this behavior?

The server is running Debian testing (3.2.0-1-amd64). The machine only has one network interface, eth0. Both iptraf and nethogs where watching this interface (and it is also the interface attached to the netgear switch.)

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Which interface is iptraf showing ? lo ? everything aggregated ? – adaptr Mar 12 '12 at 8:17
Both where looking on eth0, the only interface the machine has. – Blubber ↵ just now – Iain Mar 12 '12 at 8:22
Are you sure that the unit is MBytes/s ? – Dom Mar 12 '12 at 11:58
Yes :) I asked a couple of other people to look as well. The unit is kbytes/sec and it's showing in excess of 22000 kbytes/sec. – Blubber Mar 17 '12 at 22:17

iptraf includes "IP traffic monitor" (the top line in the menu), which displays traffic on existing TCP connections. Does it show anything?

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I will keep an eye on it, problem is that it occurs sporadically. – Blubber Mar 17 '12 at 22:18

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