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Domain Name System (DNS)
This section will deal with the analysis of the DNS packets by examining how DNS messages are formatted and the options and variables they contain. T…
The OSI Model
The Datalink ensures that messages are delivered to the proper device and translates messages from the Network layer into bits for the Physical layer…
Subnetting
There are a few different ways to approach subnetting and it can get confusing because of the complexity of some subnets and the flexibility they off…
Ethernet Protocol, CSMA/CD, Collisions
While the original 802.3 specification worked well, the IEEE realized that some upper layer protocols required an Ethertype to work properly. For exa…

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Netflow Articles:

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…
In this article, we explore the core principles of bandwidth management and examine how modern network monitoring technologies can assist in maintain…
SNMP (Simple Network Management Protocol) and Netflow are both popular protocols with admins, prized for their ability to give visibility over the ne…

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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
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
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
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
This article explains how OSPF uses Link State Advertisement (LSA) to exchange information about the network topology between routers. When a router recei…
Routing
We all understand that TCP/IP, IPX-SPX are protocols which are used in a Local Area Network (LAN) so computers can communicate between with each other and…
Routing
Open Shortest Path First (OSPF) is a popular routing protocol developed for Internet Protocol (IP) networks by the Interior Gateway Protocol (IGP) working…
Routing
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…

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…
Windows Servers
FREE Hyper-V & VMware Virtualization Backup:  FREE for Firewall.cx readers for a Limited Time!  Download Now! Windows Server 2012 Editions…
Palo Alto Networks
What makes Palo Alto Networks Next-Generation Firewall (NGFW) so different from its competitors is its Platform, Process and Architecture. Palo Alto Netwo…
Cisco Firewalls
One Appliance – One Image is what Cisco is targeting for its Next Generation Firewalls. With this vision, Cisco has created a unified software image named…