How to do it...

Once you've started iftop on centos2, switch to centos1 and run an ssh command to generate some network traffic to centos2:

$ ssh 192.168.33.11
The authenticity of host '192.168.33.11 (192.168.33.11)' can't be established.
ECDSA key fingerprint is SHA256:GwCeJ/ObTsyKxMxzazTaYvvyY3SFgxPl6ucjPDGwmao.
ECDSA key fingerprint is MD5:0d:41:ad:71:67:07:35:d4:59:07:de:41:bf:a4:b4:93.
Are you sure you want to continue connecting (yes/no)? yes
Warning: Permanently added '192.168.33.11' (ECDSA) to the list of known hosts.
vagrant@192.168.33.11's password: 
Last login: Sun Aug 19 15:04:49 2018 from 10.0.2.2
$

Back on centos2, you should see a brief entry in your network screen that shows activity:

In my ssh session on centos1 (which is now connected to centos2), I've started top to generate a stream of traffic.

At the bottom of your window, you will see the following values:

  • TX
  • RX
  • TOTAL:

These values are total traffic transferred, received, and total.

To the right we have the rates averaged over 2, 10, and 40 seconds.

Clicking back to centos1 and stopping, then starting top, will cause the RX values to rise, as you've sent keystrokes over the connection.

At the top of the window, you can see a visual representation of the traffic:

This displays traffic sent back to 192.168.33.10 (centos1) and the traffic received in a somewhat readable format.

The scale for the transfer rate is at the top, and varies depending on quantity.

In a real-world scenario, this type of information can be invaluable, as it offers an at-a-glance way of seeing who might be hammering your server.

If we swap to watching eth0 traffic, then restart chronyd, we can see more servers being connected to:

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