Articles Tagged ‘networking’

Cisco Data Center User Group

official-cisco-data-center-user-group-melbourne-australia-1Australia’s first official Cisco Data Center User Group is a reality!

Originally inspired by Cisco Champions Chris Partsenidis and Derek Hennessy, and backed up by Cisco Systems we decided it was time to get Australia’s Cisco community together. Monthly meetings are held at a great location in Melbourne CBD along with free beer & food and great discussions!

Fibre Optic Cables - Single-Mode Multi-Mode - Advantages, Construction and Elements

Fibre Optic Cables - Single-Mode Multi-Mode - Advantages, Construction and ElementsIn this article, we'll talk about Fiber optic cables and how it has changed the design and implementation of network infrastructures, providing high Gigabit speeds, increased security, flexibility and complete immunization from electromagnetic interference.

In the 1950s, more research and development into the transmission of visible images through optical fibers led to some success in the medical world where it was being used in remote illumination and viewing instruments. In 1966 Charles Kao and George Hockham proposed the transmission of information over glass fiber and realized that to make it a practical proposition, much lower losses in the cables were essential.

This was the driving force behind the developments to improve the optical losses in fiber manufacturing and today optical losses are significantly lower than the original target set by Charles Kao and George Hockham.

The Advantages of Using Fiber Optics

Because of the low loss, high bandwidth properties of fiber cables they can be used over greater distances than copper cables. In data networks this can be as much as 2 km without the use of repeaters. Their light weight and small size also make them ideal for applications where running copper cables would be impractical and, by using multiplexers, one fiber could replace hundreds of copper cables. This is pretty impressive for a tiny glass filament, but the real benefit in the data industry is its immunity to Electro Magnetic Interference (EMI), and the fact that glass is not an electrical conductor

Fiber Optic Cable

Figure 1. A Fiber Optic Cable

Because fiber is non-conductive it can be used where electrical isolation is needed, for instance, between buildings where copper cables would require cross bonding to eliminate differences in earth potentials. Fibers also pose no threat in dangerous environments such as chemical plants where a spark could trigger an explosion. Last but not least is the security aspect; it is very, very difficult to tap into a fiber cable to read data signals.

Fiber Construction

There are many different types of fiber cable, but for the purposes of this explanation we will deal with one of the most common types -- 62.5/125 micron loose tube. The numbers represent the diameters of the fiber core and cladding, these are measured in microns which are millionths of a meter.

Construction of Fiber Optic Cable - Components

Figure 2. Construction of Fiber Optic Cable - Components

Loose tube fiber cable can be indoor or outdoor, or both. Outdoor cables usually have the tube filled with gel to act as a moisture barrier to the ingress of water. The number of cores in one cable can be anywhere from 4 to 144.

Over the years a variety of core sizes have been produced but these days there are three main sizes that are used in data communications, these are 50/125, 62.5/125 and 8.3/125. The 50/125 and 62.5/125 micron multi-mode cables are the most widely used in data networks, although recently the 62.5 has become the more popular choice. This is rather unfortunate because the 50/125 has been found to be the better option for Gigabit Ethernet applications.

ST Duplex Patch Lead

Figure 3. ST Duplex Patch Lead

The 8.3/125 micron is a single-mode cable which until now hasn't been widely used in data networking due to the high cost of single mode hardware. Things are beginning to change because the length limits for Gigabit Ethernet over 62.5/125 fiber has been reduced to around 220m and now using 8.3/125 may be the only choice for some campus size networks.

What's the Difference Between Single-Mode and Multi-Mode?

With copper cables larger size means less resistance and therefore more current, but with fiber the opposite is true. To explain this we first need to understand how the light propagates within the fiber core.

Light propagation

Light travels along a fiber cable by a process called 'Total Internal Reflection' (TIR); this is made possible by using two types of glass which have different refractive indexes. The inner core has a high refractive index and the outer cladding has a low index. This is the same principle as the reflection you see when you look into a pond. The water in the pond has a higher refractive index than the air and if you look at it from a shallow angle you will see a reflection of the surrounding area, however, if you look straight down at the water you can see the bottom of the pond


Figure 4. Light transmitted through a Fiber Optic cable

At some specific angle between these two views points the light stops reflecting off the surface of the water and passes through the air/water interface allowing you to see the bottom of the pond. In multi-mode fibers, as the name suggests, there are multiple modes of propagation for the rays of light. These range from low order modes, which take the most direct route straight down the middle, to high order modes, which take the longest route as they bounce from one side to the other all the way down the fiber.

Light bouncing while it travels inside a Fiber Optic cable

Figure 5. Light bouncing while it travels inside a Fiber Optic cable

This has the effect of scattering the signal because the rays from one pulse of light arrive at the far end at different times; this is known as Intermodal Dispersion (sometimes referred to as Differential Mode Delay, DMD). To ease the problem, graded index fibers were developed. Unlike the examples above which have a definite barrier between core and cladding, these have a high refractive index at the centre which gradually reduces to a low refractive index at the circumference. This slows down the lower order modes allowing the rays to arrive at the far end closer together, thereby reducing intermodal dispersion and improving the shape of the signal.

So what about the single-mode fiber?

Well, what's the best way to get rid of Intermodal Dispersion? Easy, only allow one mode of propagation. So a smaller core size means higher bandwidth and greater distances. Simple as that!

 Back to Network Cabling Section 15 Years’ Success – New Logo – New Identity – Same Mission

This December (2015) is a very special one. It signals 15 years of passion, education, learning, success and non-stop ‘routing’ of knowledge and technical expertise to the global IT community.

What began 15 years ago as a small pitiful website, with the sole purpose of simplifying complicated networking & security concepts and sharing them with students, administrators, network engineers and IT Managers, went on to become one of the most recognised and popular network security websites in the world.

Thanks to a truly dedicated and honest team, created mainly after our forums kicked in on the 24th of October 2001, was able to rapidly expand and produce more high-quality content that attracted not only millions of new visitors but also global vendors.

Our material was all of a sudden used at colleges and universities, was referenced by thousands of engineers and sites around the world, then Cisco Systems referenced resources in its official global CCNA Academy Program!

Today we look back and feel extremely proud of our accomplishment and, after all the recognition, positive feedback from millions and success stories from people who moved forward in their professional career thanks to, we feel obligated to continue working hard to help this amazing IT community.

Readers who have been following since the beginning will easily identify the colourful logo that has been with us since the site first went online. While we’ve changed the site’s design & platform multiple times the logo has remained the same, a piece of our history to which users can relate.

Obviously times have changed since 2000 and we felt (along with many other members) that it was time to move forward and replace our logo with one that will better suit the current design & community, but at the same time make a real statement about who we are and what our mission is.

So, without any further delay, we would like to present to our community the new logo: - New Logo - The Site for Networking Professionals


Decoding The New Logo

Our new logo communicates what and its community are all about. The new slogan precisely explains what we do: Route (verb) Information (knowledge) and Expertise to our audience of Network Professionals – that’s you. Of course, we still remain The No.1 Site for Networking Professionals :)

The icon on the left is a unique design that tells two stories:

  1. It’s a router, similar to Cisco’s popular Visio router icons, symbolising the “routing” process of information & expertise mentioned in our slogan.
  2. It symbolises four IT professionals: three represent our community (red) – that’s you, and the fourth (blue) is the team. All four IT professionals are connected (via their right arm) and share information with each other (the arrows).

We hope our readers will embrace the new logo as much as we did and continue to use as a trusted resource for IT Networking and Security topics.

On behalf of the Team - Thank you for all your support. We wouldn’t be here without you.

Chris Partsenidis
Founder & Editor-in-Chief

Linux Administration

The Linux Administration section covers a number of utilities, programs and articles used to administer the Linux Operating System. Our articles cover popular topics such as: Linux user and group administration, Network configuration, Linux Runtime levels, TCP/IP Configuration files, system quotas, performance monitoring, text/file editors (Vi) and more.

Our articles cover all popular Linux distributions such as Redhat Linux, Fedora, Mandrake, Suse Linux, Slackware, Ubuntu, openSUSE, Gento Linux and more.


Our popular Networking section is well-known for the variety of high-quality articles covering topics such as Network Protocols, OSI Model, IPv4 & IPv6 addressing, Subnetting, Routing, Routing protocols, CIDR-Supernettting, Ethernet technologies, VLAN Networks, Virtual Trunk Protocol (VTP), Network Address Translation (NAT), Firewalls, WAN Technologies and much more.

All articles make use of our award-winning diagrams and contain illustrations aimed to help make the learning process as easy as possible no matter how complex the topic might be.

We hope you enjoy this section and manage to master all information included.

Networking News

This section contains articles covering Networking news from around the world.

Other Articles

Articles published in this sub-category cover a number of topics and fall within multiple other categories. These articles are of general interest and cover topics such as Security, general Windows software, technologies and many more.

We will continue populating this section as we progress and will happily include any suggestions from our readers.


Routing is one of the most important features in a network that needs to connect with other networks. In this page we try to explain the difference between Routed and Routing protocols and explain different methods used to achieve the routing of protocols.The fact is that if routing of protocols was not possible, then we wouldn't be able to comminucate using computers because there would be no way of getting the data across to the other end !


Routing is used for taking a packet (data) from one device and sending it through the network to another device on a different network. If your network has no routers then you are not routing. Routers route traffic to all the networks in your internetwork. To be able to route packets, a router must know the following :

  • Destination address
  • Neighbor routers from which it can lean about remote networks
  • Possible routes to all remote networks
  • The best route to each remote network
  • How to maintain and verify routing information

Before we go on, I would like to define 3 networking terms :

Convergence: The process required for all routers in an internetwork to update their routing tables and create a consistent view of the network, using the best possible paths. No user data is passed during convergence.

Default Route: A "standard" route entry in a routing table which is used as a first option. Any packets sent by a device will be sent first to the default route. If that fails, it will try alternative routes.

Static Route: A permanent route entered manually into a routing table. This route will remain in the table, even if the link goes down. It can only be erased manually.

Dynamic Route: A route entry which is dynamically (automatically) updated as changes to the network occur. Dynamic routes are basically the opposite to static routes.

We start off with the explanation of the IP routing process and move onto routed protocols, then tackle the routing protocols and finally the routing tables. There is plenty to read about, so grab that tea or coffee and let's start!

Windows 2000 Server

This category contains articles covering the installation and configuration of Windows 2003 Server services. All articles contain step-by-step screenshots to make them easier to follow. No matter how novice or advanced your knowledge on Windows 2000 Technologies is, following the provided instructions is very easy and straight-forward.

We hope you enjoy the provided articles and welcome your feedback and suggestions.

Windows Server 2016 – Hyper-V Virtualization Update

windows-server-2016-new-hyper-v-virtualization-features-1The new Hyper-V virtualization features offered by Windows Server 2016 are planning to make major changes in the virtualization market. From Nested Hyper-V, revolutionary security, new management options to service availability, storage and more.

Learn all about the new hot virtualization features offered by Windows Server 2016 by attending the free webinar hosted by Altaro and presented by two Microsoft Cloud and Datacenter Managerment MVP’s Andy Syrewicze and Aidan Finn.

To learn more about the free webinar and register click here.

Articles To Read Next:


Cisco Routers

  • SSL WebVPN
  • Securing Routers
  • Policy Based Routing
  • Router on-a-Stick

VPN Security

  • Understand DMVPN
  • GRE/IPSec Configuration
  • Site-to-Site IPSec VPN
  • IPSec Modes

Cisco Help

  • VPN Client Windows 8
  • VPN Client Windows 7
  • CCP Display Problem
  • Cisco Support App.

Windows 2012

  • New Features
  • Licensing
  • Hyper-V / VDI
  • Install Hyper-V


  • File Permissions
  • Webmin
  • Groups - Users
  • Samba Setup