Category Linux

Filtering SSH Packets with Tcpdump on Port 22

Tcpdump is a command-line packet analysis tool. We can use tcpdump to capture ssh traffic to troubleshoot connection issues and look for potential security issues on a network.   What is SSH? SSH, which stands for Secure Shell, is a…

Using Tcpdump to Filter DNS Packets

Tcpdump is a very powerful Linux command to capture DNS packets. DNS is short for Domain Name System. It is a database that links meaningful names to a specific IP address. We can use tcpdump to filter DNS packets to…

Capture Ping Packets With Tcpdump

ICMP is a network layer protocol used by network devices to diagnose network communication issues. Tcpdump command on Linux can be used to capture network packets. We can use the following examples to capture ICMP and ICMPv6 packets with tcpdump…

Filtering DNS with Tcpdump on Port 53

If you’re a Linux system administrator, then you’re probably familiar with DNS, which is a critical component of networking.  TCPdump is a powerful Linux command that can help you capture and filter network packets. With TCPdump, you can analyze DNS…

3 Ways to make Top Command sort by Memory

Top is a very powerful command to periodically display a sorted list of system processes. The default sorting key is %CPU on Linux. Below we collect 3 ways to sort processes by memory. Understanding top command in Linux The top…