CCNA Networking Fundamentals: Part 3

Today we will look a little more closely at addressing, specifically network addressing (there are more categories we will discuss later on).  When you look at an Internet Protocol (IP) address, it can seem like a totally foreign language, mostly because it is not readily familiar.  One word to get used to with IP addresses is octet, which means “eight of something”, or “group of eight.”  The reason for this is that the smallest unit of the addressing, based on binary, is a bit (remember, which is either a 1 or 0), and there are eight bits in a byte.  Each decimal number is  byte or octet, hence the meaning of the word in this particular context.  Here is an example of an actual IP Address: 24.6.12.41. 

Each part of the address has significance, and refers to some part of a larger group of addresses belonging to some organization, which will also be part of a later discussion.  The hierarchy of numbers is similar to the way telephone numbers operate (it should be noted that with local number portability and cellular phones that some of these lines are blurred nowadays).  A random phone number illustrating this is as follows: 425-519-6476.  One of the somewhat invisible aspects of this set of numbers is the country code, which does not need to be used within the borders of a given nation, the US code is 1.  The whole number breakdown, with associated geography, map out this way:

1: United States

425: Washington State, Seattle Eastside Suburbs

519: City of Bellevue

6476: Unique/Individual Subscriber Number

When a person in another state pucks up the phone and dials the complete string of numbers above, the equipment knows how to send the call based on each of these numbers, moving from the most general (country) to the most specific (subscriber).  We do this often enough that at times we even know where someone is dialing to/from based on the area code.

Now let’s apply this to IP addressing, which to some extent is a little simplified, but still largely makes sense.  Here is the same type of breakdown of the phone number used previously, using the IP address 24.6.12.41.

24: Comcast Cable Communications (you can look this up at http://whois.arin.net/rest/net/NET-24-0-0-0-2/pft)

6:  Comcast San Francisco Bay Area

12.41:  Unique Customer Address

IP address usually follows this type of hierarchy, which is how Internet routers know where to send traffic.  Getting familiar with this type of concept will save you  lot of grief later, and help you in applying these concepts to the CCNA exam as well as in practical settings.

Next time we will review another foundational topic, the Open Systems Interconnection (OSI) Model

– Joe

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