Articles That Might Interest:

Ethernet Protocol, CSMA/CD, Collisions

Propagation Delay

You may know that the minimum frame size in an Ethernet network is 64 bytes or 512 bits, including the 32 bit CRC. You may also know that the maximum length of an Ethernet cable segment is 500 meters…

Cisco Routers

Cisco GRE and IPSec - GRE over IPSec - Selecting…

GRE Tunnels are very common amongst VPN implementations thanks to their simplicity and ease of configuration. With broadcasting and multicasting support, as opposed to pure IPSec VPNs, they tend to b…

Domain Name System (DNS)

The DNS Protocol - Part 2: DNS Queries & Resoluti…

This section will help you understand how the DNS queries work on the Internet and your home network. There are two ways to use the domain name system in order to resolve a host or domain name to an…

Routing

OSPF - Part 3: OSPF Adjacency & Neighbor Forming…

This is the thrid article of our 6-part OSPF series (see below) that describes how OSPF routers perform neighbor relationship and adjacency. We’ll examine how OSPF discovers neighbors by sending Hell…

TCP - UDP Protocol Analysis

Transmission Control Protocol - Part 3: The TCP H…

This article shows the TCP Header and Segment. We explain where the TCP Header and Segment are located in an Ethernet frame and also briefly view the available options in the TCP Header. Our easy-to-…

Linux - Unix

Installation and Configuration of Linux DHCP Serv…

For a cable modem or a DSL connection, the service provider dynamically assigns the IP address to your PC. When you install a DSL or a home cable router between your home network and your modem, your…

Network Address Translation - NAT

Network Address Translation (NAT) Concepts

Before we dive into the deep waters of NAT, we need to make sure we understand exactly what NAT does. So let me give you the background of NAT, why it's here today and how it works. Even though there…

Windows Servers

Introduction To Windows Server 2012 R2 Virtualiza…

FREE Hyper-V & VMware Backup: FREE for Firewall.cx readers for a Limited Time! Download Now! Virtualization is an abstraction layer that creates separate distinct virtual environmen…

Cisco Routers

How To Configure Dynamic DNS Server On A Cisco Ro…

Hosting your own webserver or email server would normaly require a static IP address from your ISP. This ensures that your services are always reachable using the same IP address or domain name. If…

ICMP Protocol

ICMP Protocol - Part 2: Echo / Echo Reply (Ping)…

As mentioned in the previous page, an Echo is simply what we networking engineers call a 'ping'. The Echo Reply is, as most would guess, the 'ping reply'. ICMP Echos are used mostly for trouble…

VPN Services & Guides

DNS Leak Testing & Protection – How to Avoid Expo…

Despite innovations in security and technology, it’s difficult to remain anonymous online. Identifying information is seemingly everywhere – from malicious JavaScript tracking to the location service…

Cisco Routers

Cisco Router 'Privileged' Mode

To get into Privileged Mode we enter the "Enable" command from User Exec Mode. If set, the router will prompt you for a password. Once in Privileged Mode, you will notice the prompt changes from ">…