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Oct 2019

Iftop measures the data flowing through individual socket connections, and it works in a manner that is different from Nload. Iftop uses the pcap library to capture the packets moving in and out of the network adapter, and then sums up the size and count to find the total bandwidth under use.

Although iftop reports the bandwidth used by individual connections, it cannot report the process name/id involved in the particular socket connection. But being based on the pcap library, iftop is able to filter the traffic and report bandwidth usage over selected host connections as specified by the filter.

Install iftop on CentOS/RHEL/Red Hat/Fedora Linux

  yum install iftop -y

Using iftop

From the command line, simply enter:

  iftop -n

The -n option prevents iftop from resolving ip addresses to hostname, which causes additional network traffic of its own.

By default, iftop runs on the first listed interface, you can specify the interface you wish to monitor by using the following:

  iftop -i eth3 -n

The above command will run iftop and monitor traffic on interface eth3. See below for an example iftop output.

Example 1 on MGMT Interface:

                    12.5Kb              25.0Kb              37.5Kb              50.0Kb         62.5Kb
eri-4e-962953                        =>                            4.99Kb  17.5Kb  17.5Kb
                                     <=                                       2.97Kb  3.15Kb  3.15Kb
eri-4e-962953                        =>                           2.46Kb  3.65Kb  3.65Kb
                                     <=                                       4.12Kb  5.52Kb  5.52Kb
eri-4e-962953                        =>                           1.89Kb  2.08Kb  2.08Kb
                                     <=                                       3.18Kb  1.87Kb  1.87Kb
eri-4e-962953                        =>                               0b   1.73Kb  1.73Kb
                                     <=                                          0b   1.37Kb  1.37Kb
eri-4e-962953                        =>                  0b   0.99Kb  0.99Kb
                                     <=                                          0b   1.29Kb  1.29Kb                      =>                                  0b      0b      0b
                                     <=                                          0b    922b    922b

TX:             cum:   32.4KB   peak:   57.6Kb                       rates:   9.34Kb  26.0Kb  26.0Kb
RX:                    17.6KB           23.5Kb                                10.3Kb  14.1Kb  14.1Kb
TOTAL:                 50.1KB           81.1Kb                                19.6Kb  40.0Kb  40.0Kb

Example 2 on Data Interface:

                    1.86Gb              3.73Gb              5.59Gb              7.45Gb         9.31Gb
└───────────────────┴───────────────────┴───────────────────┴───────────────────┴────────────────────                          =>                           37.2Mb  33.2Mb  33.5Mb
                                     <=                                          0b      0b      0b                      =>                                  0b      0b      0b
                                     <=                                       1.24Kb   507b    444b

TX:             cum:    249MB   peak:   39.2Mb                       rates:   37.2Mb  33.2Mb  33.5Mb
RX:                    3.10KB           1.23Kb                                1.24Kb   507b    444b
TOTAL:                  249MB           39.2Mb                                37.2Mb  33.2Mb  33.5Mb
iftop.txt · Last modified: 2023/03/09 22:35 by