Networking 101

Networking 101 is written for those who have basically never heard of networking before and want to know what it’s about. After reading this, you will have a better idea of what to expect to learn in a post-secondary networking program.

 

What Is A Network?

 

You may never have considered this before, but when you’re at home browsing the Internet with your laptop, how does the website get to your screen? As far as most us know, it just appears and that’s all there is to it. The reality is, electrons are literally travelling from your laptop to the server that is hosting the website.

The medium on which these electrons are travelling on is the network.

networking-101-figure-1a

 

What Is Cisco?

 

Cisco is a company that develops network operating systems and manufactures network hardware that use the same. They are dominant in enterprise networking and learning how to configure their software is what your network career will be all about, as knowledge and experience with their products are in high demand.

 

Network Components: Physical

 

Networks are comprised of common hardware devices, which include:

 

Switches

switches-catalyst-3850-48t-s-switch

Switches connect computers together so they can communicate in the Local Area Network (LAN). For example, if you have an office with multiple computers and a printer, plugging them all into the switch will allow the computers to talk to each other and the printer.

 

Routers

cisco-4331-router

Routers allow you to communicate with a Wide Area Network (WAN), which is a larger network outside of your LAN. The most common use for a router is for accessing the Internet.

 

Access Points

cisco-1700-ap

Wireless access points are used when you need to extend your LAN to areas where wiring isn’t possible, and for accommodating wireless devices.

 

Clients

Dell PowerEdge 12G family image, featuring PowerEdge M520 blade servers in a PowerEdge M1000e modular blade enclosure, a PowerEdge T320 tower server, and PowerEdge R320, R420, and R520 rack servers.

Clients are network devices such as computers and phones that access and utilize the network. Without them, you wouldn’t need a network. It would be like building a road that no cars would ever drive on.

 

Network Components: Logical

 

All network hardware have a logical (software) component to it. Things don’t just work because they’re physically compatible. There are end to end communication protocols that instruct data on how to behave. Understanding how things work logically and configuring network devices to act accordingly is the primary job of network specialists.

To provide an example, let’s consider how two computers connected to a switch are able to logically communicate with each other.

 

networking-101-figure-2a

 

When sending mail, you specify the return address and destination address on the envelope so that the post office knows what to do with it. In the same way, computers attach the return and destination addresses on their data before sending it out to the switch. In networking, there are IP addresses and MAC addresses.

IP addresses are logical addresses assigned to PC’s. It can be configured manually, or automatically.

MAC addresses are a hardware address that is “burned” into the network card of the PC and is globally unique (no other network card will have the same MAC address). Having a unique IP and MAC address is necessary within the LAN for the same reason that two houses don’t have the exact same address. Because the person delivering the mail wouldn’t know which house to bring it to.

In order for PC-A (the source) to communicate with PC-B (the destination), it needs to know 4 things:

  • Source IP Address and Source MAC Address (return address)
  • Destination IP Address and Destination MAC Address (destination address)

networking-101-figure-2b

As you can see from Figure 2b, PC-A already knows three of the four addresses it needs to be able to send data to PC-B. The source IP and MAC address are known because they belong to itself. The destination IP is known because something (a directory, an application, or the user himself) told you.

In order to find the missing piece, the destination MAC, PC-A will use a protocol called Address Resolution Protocol (ARP). It works by sending a broadcast to everyone on the LAN that asks “Who is 192.168.1.2?” This is the equivalent of finding someone in a room by shouting so that everyone in the room can hear you.

Everyone who is not 192.168.1.2 will ignore the message, however PC-B will reply saying “That’s me. Here is my MAC address”.

You might be wondering how PC-B is able to reply if he’s missing the destination MAC address of PC-A. He is able to reply because when he received the ARP request (or heard the shout), it contained PC-A’s MAC address, thus he has all four pieces of information.

networking-101-figure-2c

 

Now that PC-A has all four pieces of information, he can now communicate with PC-B.

 

Summary

 

This concludes the brief introduction into networking. There is so much more to this, but that’s as far as we go. I hope this was somewhat insightful for you. If you’re interested in learning more, I recommend signing up for a free trial of CBT nuggets and watching their videos.

To learn how to start your network career, click here.