Network
Net
Learn about the sysctl command and the values related to the network class.
Sysctl: net.ipv4.ip_forward
The sysctl key net.ipv4.ip_forward key is used to define IP forwarding of IPv4 network packets. Learn about the possible values of this key and their meaning.
How to see the the network IP address of your system
Show the IP address of your system with the help of the ip command.
How to see the IP address of your internet connection
Show the IP address of your internet connection using the dig command.
How to see which DNS server is used
Find the active DNS server being used by reviewing the network configuration, including common commands to query this information.
Apt-file
The command apt-file can help with discovering which files belong to a package or what package installed or provides them.
Networking
Everything related to networking, from the network configuration up to DNS resolving. Test and configure your system with these articles.
How to see the number of open connections on Linux
Show the number of open connections using the ss command on Linux.
Iftop
The command iftop shows ongoing bandwidth usage on one or more network interfaces and is a great tool for troubleshooting network issues.
How to see active connections and bandwidth usage on Linux
Show actual bandwidth usage and active connections using the iftop tool on Linux.
Show to clear the DNS cache with systemd
Learn how to inspect and clear the DNS cache when using the systemd resolver daemon.
Resolvectl
The command resolvectl provides details about systemd-resolved, the name resolution daemon.
Network
Articles and information about troubleshooting network performance issues and monitoring network statistics
How to show network TCP statistics and counters
Show counters related to the TCP connections by using the nstat command. This small utility will quickly retrieve the related statistics and display them.
How to see errors and dropped packets on a network interface on Linux
Show the network link details using the ip command to find out if a network has errors or dropped packets on a Linux system.
How to see the default gateway on Linux
Show the network routing table to discover the default gateway used on a Linux system.
How to see which process is using a port
Show which process is already opened an UDP or TCP port on Linux by using the ss command.
How to see open ports on Linux
Show which UDP/TCP ports are opened on a Linux system, including the related process. Use the ss tool to see more details about these sockets.
Networking: Frequently Asked Questions
Frequently asked questions about networking, such as DNS, IP configuration, TCP/UDP details, and more.
How to see the TTL value of a DNS record
Learn how to query the Time To Live (TTL) for a DNS record by using the dig tool.
BPFILTER: the next-generation Linux firewall
BPFILTER is one of the newer features to provide traffic filtering. Learn how it works and why it may replace iptables as the firewall on Linux systems.
Beginners guide to traffic filtering with nftables
The replacement of iptables is known as nftables. In this article, we learn to install nftables and configure it, to secure your Linux systems.
The purpose of the /etc/networks file
Also wondering what some files are used for on Linux systems? In this article we have a look at the /etc/networks file.
Differences between iptables and nftables explained
An overview of the differences between firewall technologies iptables and nftables. We highlight the major differences like simplicity and management.
Linux Security Guide for Hardening IPv6
Extensive guide to help you secure your IPv6 configuration on Linux. From initial set-up to hardening the kernel with sysctl.
List network interfaces on Linux
Show the available network interfaces and information on Linux with the right tools. We cover common replacements for iptables and netstat, with examples.
Which Linux process is using a particular network port?
Seeing the 'address in use' error or need to find out which process is listening to a particular port on Linux? Here are the tools to find out!
Filtering ARP traffic with Linux arptables
Filtering ARP traffic is easy with the arptables utility. In this article we look at the possibilities of arptables and provides example of using it.
How to clear the ARP cache on Linux?
Clearing the ARP cache on Linux is easy with the arp or ip utility. This blog post will help you to clear the cache with examples for both utilities.
Linux Audit: Auditing the Network Configuration
This article describes how to audit the network configuration of Unix and Linux based systems, with useful tips for auditors and system administrators.