How to Monitor Network Bandwidth on Linux Server

Introduction

Monitoring network performance is important for preventing malfunctions and ensuring quality. Such a practice tells you whether your network is running slow and what may be the cause of such an issue. This is done by monitoring your network bandwidth usage.

There are many different tools for monitoring network traffic on a Linux server. Each option has its strengths and weaknesses. Most of the command-line utilities are designed to be lightweight and easy to use. Some are designed to present a basic overview, while others provide detailed data.

This guide compares the best Linux network monitoring tools.

Prerequisites

• Access to a user account with sudo or root privileges
• For CentOS and RHEL Linux, the EPEL (Extra Packages for Enterprise Linux) repositories must be available.
• A package manager tool (yum or apt)
• A terminal window/command line (Ctrl-Alt-T, Ctrl-Alt-F2)

9 Best Network Monitoring Tools For Linux

If you are looking for a quick display of network bandwidth, a command-line monitoring tool will do the job. If you need a detailed graph of usage for the month, graphical options may provide a better solution.

Overall usage reports can help determine bandwidth requirements, while more detailed process-level reports can help identify the source of high bandwidth usage.

Real-time reporting can alert you to usage spikes or unusual patterns when they occur.

Before You Start, Install EPEL

CentOS users first need to install the EPEL software.

For RHEL and CentOS 7.x:

1. Open a terminal window, and enter the following:

yum -y install epel-release

2. Refresh the repositories:

yum repolist

Linux servers are often configured without a graphical interface to save system resources. These applications can run and display from a command line.

iftop Display Bandwidth Usage

If you are familiar with the top command for monitoring processor usage, you will find the iftop command very similar. iftop provides a real-time display of bandwidth usage by individual connection. It also generates an overview of the amount of bandwidth being used.

One limitation in iftop is that it does not track traffic by process ID (PID).

To install iftop:

RHEL / CentOS

yum install iftop -y

Debian / Ubuntu

sudo apt-get install iftop

To monitor a different network interface, e.g: eth0 , you would need to pass the interface name to the iftop command using the -i parameter:

# iftop -i eth0

To disable hostname lookups, use the -n flag.

# iftop -n  eth0

To turn on port display, use the -P switch.

# sudo iftop -P eth0

This concludes our tutorial. For more information on how to use iftop, please refer to iftop’s website.

nload Displays Network Usage

nload is a command-line utility to monitor network traffic. This tool only reports in-traffic and out-traffic. It displays a graph, which is helpful for a quick overview of network traffic. However, nload has a disadvantage as it does not display traffic by PID or by socket.

To install nload:

RHEL / CentOS

yum –y install nload

Debian / Ubuntu

sudo apt-get install nload

nload – Monitor bandwidth usage on Linux

NetHogs Monitor Network Traffic Bandwidth

NetHogs generates real-time reports of network usage. One advantage of NetHogs is that it sorts by process/application and usage. This makes it a good utility for tracking bandwidth spikes (if you can launch it in time).

To install NetHogs:

RHEL / CentOS

yum –y install nethogs

Debian / Ubuntu

sudo apt-get install nethogs

How to Use NetHogs to Monitor Bandwidth By Process

To run the nethogs utility, type the following command under red-hat-based systems.

# nethogs

On Debian-based Linux, you must have root permissions, so run with the sudo command as shown.

$ sudo nethogs

Following are the nethogs command-line options. Using ‘-d‘ to add a refresh rate and ‘device name‘ to monitor specific given device or devices bandwidth (default is eth0).

For example, to set 5 seconds as your refresh rate, then type the command as.

# nethogs -d 5

$ sudo nethogs -d 5

To monitor specific device (eth0) network bandwidth only, use the command as.

# nethogs eth0

$ sudo nethogs eth0

bmon Bandwidth Monitor and Rate Estimator

bmon monitors bandwidth utilization, along with keeping a running rate estimate. It breaks out usage by device, allowing you to track bandwidth across multiple network adapters. Another positive feature is that it creates a graph, which lets you see bandwidth usage at a glance.

To install bmon:

RHEL / CentOS

sudo yum install bmon

Debian / Ubuntu

sudo apt-get install bmon

How to Use bmon Bandwidth Monitoring Tool in Linux

Run it as below (for starters: RX means received bytes per second and TX refers to transmitted bytes per second):

$ bmon

To view more detailed graphical statistics/information of bandwidth usage, press d key and refer screnshot below.

Press [Shift + ?] to view the quick reference below. To exit the interface, press [Shift + ?] again.

The flag -p sets a policy defining which network interfaces to display, in the example below, we will be monitoring the eth0 network interface:

$ bmon -p eth0

To use bit per second instead of bytes per second, use the -b flag like so:

$ bmon -bp eth0

$ bmon -r 5 -p eth0

vnStat Network Traffic Monitor

VnStat works by running a daemon that captures and records bandwidth data. It reads from the kernel to stay light on resource usage. It can run in real-time by using the –l option. The real value lies in persistent records. As the daemon runs, it collects and stores bandwidth usage data.

The vnstati command can be used to display usage statistics. VnStat is best suited for statistical reporting.

To install vnStat:

RHEL / CentOS

yum -y install vnstat

Debian / Ubuntu

sudo apt-get install vnstat

Once installed, the default configuration should work for most people. Default will run on Network Interface is eth0. If you need to change the Network Interface, you will need to edit the following file.

nano /etc/vnstat.conf

Next, we need to create a database where the data will be collected and stored.

vnstat -u -i eth0
chown vnstat:vnstat /var/lib/vnstat/eth0

Finally start the service and start collecting data.

systemctl start vnstat
systemctl enable vnstat

Using vnstat

Using VnStat, you can view bandwidth statistics per day, per month and per hour. It also provides the option to display real-time statistics.

Show stats for a day

vnstat -d

Show statistics for a month

vnstat -m

Show stats for a week

vnstat -w

Show stats for an hour

vnstat -h

Show top 10 network statistics

vnstat -t

Real-time stats display

vnstat -l

iPerf/iPerf3 Network Bandwidth Measurement Tool

iPerf is for monitoring bandwidth by protocol, such as TCP and UDP.

This tool is best for tweaking and maximizing network performance for a particular protocol. One limitation is that it requires both a server and a client to test.

To install iPerf:

RHEL / CentOS:

yum –y install iperf3

Debian / Ubuntu:

sudo apt-get install iperf3

Graphical Bandwidth Monitoring Tools

The following tools are more graphical in their interface and display. Many of them offer a more robust suite of monitoring than the more simple command-line tools.

Nagios Core Monitors Systems, Networks and Infrastructure

Nagios has been a trusted open-source bandwidth monitoring tool for almost 20 years.

The interface runs through a web browser and offers multiple monitoring vectors. It can monitor across multiple network services, such as HTTP, POP3, and SMTP. It also has the ability to send notifications, such as when a problem occurs, or when an issue is resolved.

Nagios Core is a free open-source application. A paid, supported version is also available.

Zabbix Application and Network Monitoring Tool

Zabbix is a free open-source bandwidth monitoring application.

It runs in PHP in a web browser. Zabbix aims to simplify network monitoring, and it includes device and application monitoring. It generates data logs, which can be used to track and improve performance, and it can quickly scale between large and small applications. One advantage to Zabbox is that it can be used for free, even in large commercial applications.

You can refer to zabbix installation instructions at:

https://green.cloud/docs/how-to-install-zabbix-server-on-centos-7/

Cacti Network Monitoring and Graphing Tool

Cacti is a network monitoring tool that uses PHP and runs in a browser window.

The core strength in Cacti is its data collection and reporting. Cacti is not just limited to network bandwidth, it can also track other metrics like user permissions and access. Cacti uses scripts to gather data and compile it into meaningful charts and graphs.

You can refer to the installation instructions and Cacti Network Monitoring and Graphing Tool at:

https://green.cloud/docs/how-to-monitor-window-servers-with-cacti-using-snmp/
https://green.cloud/docs/how-to-monitor-device-using-icmp-ping-on-cacti-monitoring-tool/

Conclusion

This guide covered the top Linux system monitoring and network bandwidth tools. Experiment and compare a few options, consider your needs and the software capabilities to find one that suits you best.