Monitoring current network usage
One utility to display the current network usage is nload. This can be useful when you need to monitor the ingress/egress bandwidth usage directly on Linux servers and this can be used for specific network devices.
Installation
You can install nload through yum on Red Hat/CentOS operating systems, with apt on Debian based distributions or dnf with Fedora . Here are several variations:
RHEL & CentOS:
sudo yum install nload
Debian & Ubuntu:
sudo apt install nload
Fedora:
sudo dnf install nload
The nload utility can be installed from the epel repository on Red Hat/CentOS distributions.
If epel is not already installed on the RHEL & CentOS environment, this can be installed with:
sudo yum install epel-release
Live network bandwidth monitoring
nload can be used via a console or SSH session. This utility has several options that vary the output.
By default this will auto-detect devices and you can switch between devices with the left and right arrow keys.
The device displayed can be seen at the top of the nload output - for example:
Device lo [127.0.0.1] (1/2):
Or to show all devices (suppressing traffic graphs), use the command nload -m - this will something similar to this in the standard output:
Device eth0 [10.0.0.20] (1/2):
=============================================================================================================================
Incoming: Outgoing:
Curr: 13.44 kBit/s Curr: 52.41 kBit/s
Avg: 48.49 kBit/s Avg: 82.66 kBit/s
Min: 4.91 kBit/s Min: 8.23 kBit/s
Max: 108.29 kBit/s Max: 732.95 kBit/s
Ttl: 28.27 GByte Ttl: 22.68 GByte
Device lo [127.0.0.1] (2/2):
=============================================================================================================================
Incoming: Outgoing:
Curr: 13.21 kBit/s Curr: 13.21 kBit/s
Avg: 75.44 kBit/s Avg: 75.44 kBit/s
Min: 2.31 kBit/s Min: 2.31 kBit/s
Max: 671.77 kBit/s Max: 671.77 kBit/s
Ttl: 21.72 GByte Ttl: 21.72 GByte
The default time window is '300' milliseconds between average calculations. It can be set to a custom time window with nload -a <time> - for example to update this to 150 milliseconds you would perform the command:
nload -a 150
Modifying the default display interval is also possible - by default this value is 500 milliseconds. The flag to update the display interval is -t and can be used as follows:
nload -t 600
Please note that specifying refresh intervals shorter than about 100 milliseconds makes traffic calculation very unprecise. Also the display may flicker using such short refresh intervals. nload tries to balance this out by doing extra time measurements, but this may not always succeed.
If there is a specific device(s) that needs to be monitored, you can specify this with the following:
nload devices device1 device2
In addition, the metrics in which the data is displayed can be customised - the default is adaptive to the amount of bandwidth being used but it can be forced with one of the subsequent variations:
nload -u K ## KByte/s
nload -u k ## KBit/s
nload -u M ## MByte/s
nload -u m ## KBit/s
nload -u G ## GByte/s
nload -u g ## GBit/s