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The OSI Model
The Presentation Layer gets its name from its purpose: It presents data to the Application layer. It's basically a translator and provides coding and…
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…
Ethernet Protocol, CSMA/CD, Collisions
Now that Fast Ethernet is here, the question becomes, "How do I start using it ?" Integrating Fast Ethernet into existing networks need not be done a…
TCP - UDP Protocol Analysis
As we have seen in the previous pages, some TCP segments carry data while others are simple acknowledgements for previously received data. The popula…

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Netflow Articles:

This article will cover the basics of Netflow, including its use cases, Netflow supported devices, Netflow history, and variants. We’ll also dive int…
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…

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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…
VLAN Networks
Deciding whether to use ISL or IEEE 802.1q to power your trunk links can be quite confusing if you cannot identify the advantages and disadvantages of eac…
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
VLANs are usually created by the network administrator, assigning each port of every switch to a VLAN. Depending on the network infrastructure and securit…

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
IGRP (Interior Gateway Routing Protocol) is a Cisco proprietary distance-vector routing protocol used in enterprise networks to exchange routing informati…
Routing
This article explains how OSPF uses Link State Advertisement (LSA) to exchange information about the network topology between routers. When a router recei…
Routing
Our previous article explained the purpose of Link State Update (LSU) packets and examined the Link State Advertisement (LSA) information contained within…

Windows Servers
In this article, we will cover more advanced DHCP features and topics such as server options, superscopes, multicast scopes, dynamic DNS, DHCP database ba…
Windows Servers
With the introduction of Hyper-V on the Windows Server platform, virtualization has quickly become the de facto standard for all companies seeking to cons…
Cisco Routers
When working with Cisco equipment that has multiple ip interfaces, a common problem engineers are faced with is trying to successfully tftp to or from the…
Network Protocol Analyzers
Firewall.cx has covered Colasoft Capsa several times in the past, but its constant improvements make it well worth revisiting. Since the last review, the…