DHCP (Dynamic Host Configuration Protocol) DHCP (Dynamic Host Configuration Protocol) is a network management protocol used to dynamically... Gateway or Router Gateway / Router IP: All the clients on a network point to a default gateway that should be used... Linux Group Management (Collection of Users) Groups are a collection of users. Assigning users to groups makes it easier to manage... Linux User Management Following document will help you understand adding new users, groups and change ACL lists in your... MAC Address and ARP Protocol MAC Address (size of address in binary 48bit): A Media Access Control address (MAC address) of a... Network Port Numbers and its Definition A network port is a number that identifies one side of a connection between two computers.... Network Switches, Routers & Internet Connection Router vs Switch... Understanding DNS Servers Root Servers: Root server -- these servers are at the base of the name server hierarchy. They... Understanding Firewall Structures in a Linux Server CentOS has an extremely powerful firewall built in, commonly referred to as iptables, but more... Understanding IP addresses and Classes IP Addresses: An IP address, short for Internet Protocol address, is an identifying number for a... Understanding Networking and Subnets Network & Hosts: IP addresses are typically made of two separate components: 1. The first... Understanding Swapfile and setting up Swap for a System Swap is space on a disk that is reserved to be used as virtual memory. When a Linux server runs... Useful Network Commands netstat - Print network connections, routing tables, interface statistics, masquerade... tcpdump Command and Usage tcpdump is a most powerful and widely used command-line packets sniffer or package analyzer tool... Understanding Email Services MUA: Mail User Agent (email client): The MUA is the front-end for the end user to manage and read... Understanding POP, IMAP, Dovecot Dovecot is an open source IMAP and POP3 email server for Linux/UNIX-like systems, written with... Installing Exim on Cent OS 6.x / 7.x Operating System: Cent os 6.x / 7.xHostname: hostname [not a registered domain name, but you can... Introduction of Exim MTA Exim is a mail transfer agent (MTA) for hosts that are running Unix or Unix-like operating... Exim Config and Log path The exim is an open source email server and it has a lot of flexible options and commands to... Understanding and Reading an Exim Maillog Reading exim log can be a confusing or complicated at first, however, having understanding of... Handling Exim Spam Queue As we see huge number of emails in a queue, first we need to find top senders, to do so, we can... Exim Shell Commands Exim's command line takes the standard Unix form of a sequence of options, each starting with a...