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Ethernet Protocol, CSMA/CD, Collisions
Late collisions, on the other hand, are not normal and are usually the result of out of spec. cabling or a malfunctioning adapter. A late collision i…
ICMP Protocol
The ICMP - Source Quench message is one that can be generated by either a gateway or host. You won't see any such message pop up on your workstation…
ICMP Protocol
The 'ICMP Destination unreachable' message is quite interesting, because it doesn't actually contain one message, but infact six! This means that the…
The OSI Model
Here we are going to explain in detail how data travels through the OSI model. You must keep in mind that the OSI model is a guideline. It tells the…

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Netflow Articles:

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…
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
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
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
Designing and building a network is not a simple job. VLANs are no exception to this rule, in fact they require a more sophisticated approach because of 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…

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
Hybrid routing protocols are a combination of distance-vector and link-state routing protocols, and are used to provide a more efficient and scalabl…
Routing
Distance Vector routing protocols use frequent broadcasts (255.255.255.255 or FF:FF:FF:FF) of their entire routing table every 30 sec. on all their interf…

Palo Alto Networks
This article’s purpose is to help you quickly master Palo Alto QoS concepts and learn to configure QoS on Palo Alto Firewalls in a simple and efficient wa…
Cisco Routers
This article serves as an extension to our popular Cisco VPN topics covered here on Firewall.cx. While we’ve covered Site to Site IPSec VPN Tunnel Between…
Cisco Routers
Our DMVPN Introduction article covered the DMVPN concept and deployment designs. We explained how DMVPN combines a number of technologies that give it its…
Cisco Switches
The Cisco Catalyst Switching Portfolio is perhaps one of the most useful Cisco PDF files, containing all Catalyst series products.  The portfolio co…