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Domain Name System (DNS)
The previous article covered the DNS Query message formats. In the article we analysed them in great detail and showed how various options are select…
TCP - UDP Protocol Analysis
Understanding how each protocol fits into the OSI Model is essential for any network engineer. This page analyses how TCP is classified as a 'transpo…
Ethernet Protocol, CSMA/CD, Collisions
The following is a description of the Ethernet Frame Format described in the IEEE 802.3 Specification. The 802.3 Specification defines a 14 byte Data…
Spanning Tree Protocol (STP)
One of the most used terms in network is LAN (Local Area Network). It’s a form of network that we encounter in our daily lives, at home, at work, stu…

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Netflow Articles:

SNMP (Simple Network Management Protocol) and Netflow are both popular protocols with admins, prized for their ability to give visibility over the ne…
In our previous article we explained how a Netflow Analyzer can help you gain visibility into your user traffic, application traffic and data flows w…
Monitoring network traffic & bandwidth usage via Netflow is mandatory for any type and size network. Gaining visibility into user traffic, applic…
This article will cover the basics of Netflow, including its use cases, Netflow supported devices, Netflow history, and variants. We’ll also dive int…

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VLAN Networks
We mentioned that Trunk Links are designed to pass frames (packets) from all VLANs, allowing us to connect multiple switches together and independently co…
VLAN Networks
It's easy to see why virtual LANs have become extremely popular on networks of all sizes. In practical terms, multiple VLANs are pretty much the same as h…
VLAN Networks
The previous article introduced the VTP protocol, we examined how it can be used within a network, to help manage VLANs and ease the administrative overhe…
VLAN Networks
While the VLAN Tagging article briefly covered the IEEE 802.1q protocol this article will continue building upon it by further analyzing the IEEE 802.1q T…

Routing
IGRP (Interior Gateway Routing Protocol) is a Cisco proprietary distance-vector routing protocol used in enterprise networks to exchange routing informati…
Routing
Routing Information Protocol (RIP) is a distance-vector routing protocol that is commonly used in small to medium-sized networks. It is one of the o…
Routing
This article covers basic OSPF concepts and operation. We explain how OSPF works, how OSPF tables are built on an OSPF-enabled router and their purpose (N…
Routing
We are going to analyse what happens when routing occurs on a network (IP routing process). When I was new to the networking area, I thought that all you…

Cisco Firewalls
Cisco’s Adaptive Security Appliance (ASA) Firewalls are one of the most popular and proven security solutions in the industry. Since the introduction of t…
Cisco Switches
This article provides in-depth analysis of DHCP Option 82 (DHCP Relay Agent) which is one of the +180 DHCP Options available to the DHCP protocol and used…
Cisco Firewalls
The Cisco ASA 5500 series security appliances have been around for quite some time and are amongst the most popular hardware firewalls available in the ma…
Cisco Routers
NAT (Network Address Translation) is a method that allows the translation (modification) of IP addresses while packets/datagrams are traversing the networ…