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Ethernet Protocol, CSMA/CD, Collisions
Here we see a logical drawing of the Fast Ethernet Data Link Layer sublayers. Data is passed down from the upper layers (such as TCP/IP or Novell Net…
Network Address Translation - NAT
Our previous article, Dynamic NAT - Part 1, covered the basic idea of Dynamic Network Address Translation. We are now going to take a closer look at…
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…
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:

SNMP (Simple Network Management Protocol) and Netflow are both popular protocols with admins, prized for their ability to give visibility over the ne…
This article will cover the basics of Netflow, including its use cases, Netflow supported devices, Netflow history, and variants. We’ll also dive int…
Monitoring network traffic & bandwidth usage via Netflow is mandatory for any type and size network. Gaining visibility into user traffic, applic…
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…

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VLAN Networks
The invention of VLANs was very much welcomed by all engineers and administrators, allowing them to extend, redesign and segment their existing network wi…
VLAN Networks
We hear about them everywhere, vendors around the world are constantly trying to push them into every type of network and as a result, the Local Area Netw…
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
Dynamic VLANs were introduced to grant the flexibility and complexity(!) that Static VLANs did not provide. Dynamic VLANs are quite rare because of their…

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 is the third article of our OSPF series which analyzes the different OSPF States routers go through during the OSPF discovery and neighbor forming pr…
Routing
Enhanced Interior Gateway Routing Protocol (EIGRP), similar to IGRP, is a Cisco proprietary routing protocol that is used to exchange routing information…

Windows Servers
Our previous article explained what Group Policy Objects (GPO) are and showed how group policies can be configured to help control computers and users wit…
Cisco Switches
It's no news that we here at Firewall.cx enjoy writing about our installations of Cisco equipment and especially devices that we don’t get to see and play…
Cisco Switches
This article covers basic and advanced configuration of Cisco Catalyst Layer-3 switches such as the Cisco Catalyst 3560G, 3560E, 3560-X, 3750, 3750E, 3750…
Cisco Routers
Introduction Let's see what it looks like to be in User-Exec mode on a Cisco router. Below, we have telneted into our lab router and are in User Exec Mod…