CCNA Blog and Study Guide

The New Year is here and with it the holidays are over.  I’ve been on a nice long 2 week break from work.  But its over when this night is done.  Over these past two weeks I’ve come to realize a few things.  Number 1, its time for a change.  I enjoy aspects of my job but overall I need a reboot.  Times are tough but if there is one thing I’ve learned over the past few years is opportunity is all around us.  But you have to bust butt a little to get results and find the opportunity.  Play the percentages.  Through enough crap at the wall, something will stick…You get the point.

Number two, I am hell bent on upping my certification status in networking and systems.  CCNA is the 1st Quarter goal along with updating my Microsoft stats with at least an MCSA in ‘03.

Number three, just be happier and don’t take everything so seriously.  I had a loss in the family over the holidays and as I sat at the funeral I just thought over and over that it could be me in the casket.  Death can’t be controlled.  And I don’t want to die unhappy.  I want to pass knowing I brought joy and support to those around me, both in family and professionally.  One of my uncles is a prime example of living a happy life with the cards you are dealt.  He is not rich but has made a good life for himself and his family.  He is happy and always with a smile to share.  I want to be that person.

By weeks end I schedule my 640-822 and get the ball rolling for 2009.  I’ll be reflecting back to this post to see where I stand through out the year.

Thoughts

While reviewing my notes, I realized I should add a small addition to the last post on subnetting.  I showed all the examples using a /n notation but nothing if a subnet mask in decimal format is given.  With the steps below, it actually is even quicker to big out the network blocks.

Example

Determine the subnet of IP address 195.17.23.17 subnet mask 255.255.252.0

1. What is the IP address block size?
   Subtract the last non-zero octets value from 256.  If there is no octet with a zero, work with the 4th octet. (ie. 255.255.255.248)

   256 - 252 = 4 is our block size

2. How do you build out the IP address blocks?
   Just as before, work in the last octet that is a non-zero in the subnet mask.

   195.17.0.0
   195.17.4.0
   195.17.8.0
   195.17.12.0
   195.17.16.0
   195.17.20.0
   195.17.24.0  … We stop here

   The answer to what subnet 195.17.23.17 sits in is 195.17.20.0.

Subnetting subnet mask, Subnetting

With so many subnetting tutorials out on the Internet and published in books, it seems overwhelming to study this topic.  I definitely believe in what works for one person, doesn’t necessarily work for other.  Everyone learns in a different way.  I’ve spent a part of the day trying different techniques to solve questions related to finding the subnet a specific IP address belongs to when given the subnet mask.

To use this technique, several things need to be understood.

• IP Address Classes
• CIDR (Classless Inter-Domain Routing) [see prior post]
• Powers of 2

It is also important to know any easy way to determine what bit each octet ends with.  For example:

32-bit IP Address:   11111111.11111111.11111111.11111111

Each . (dot) represents the 8th bit in the octet.  Therefore the first . is 8, the second . is 16, the third . is 24 and the “invisible” . at the end of the last octet is 32

First Example

Determine the subnet of IP address 195.17.23.17 /22

1. What octet are we working in?
   This is done by looking at the important end bit for each octet.  Think of it as a boundary.  Find the largest numbered boundary less then the subnet mask given.
   Since 22 is less then 24, we are in the 3rd octet.
2. What is the IP address block size?
   Take the value of /n and subtract from the next highest octet boundary found in Step 1. Take the result and apply it to the power of 2.
   24 - 22 = 2
   2 ² = 4 is our block size
3. How do you build out the IP address blocks?
   Because we know from Step 1 the octet we are working in, write out the starting subnet address in that octet and continue until we pass the address in that octet.  For this example that would be 43.
   To determine the next block of IP addresses, take the block size and add it to the number in that octet.  In this example it would be adding 4 in the 3rd octet.195.17.0.0
   195.17.4.0
   195.17.8.0
   195.17.12.0
   195.17.16.0
   195.17.20.0
   195.17.24.0 … We can stop here
   The answer to what subnet 195.17.23.17 sits in is  195.17.20.0.

Second Example

This next example just works the problem out with the commentary.   This should show how little work really needs to be done to get to the answer.

Determine the subnet of IP address 187.21.36.180 /19

1. What octet are we working in?
   19 < 24 (the boundary of the 3rd octet)
   Answer: 3rd octet
2. What is the IP address block size?
   24 - 19 = 5
   2 ⁵ = 32
3. How do you build out the IP address blocks?
   187.21.0.0
   187.21.32.0
   187.21.64.0 …We can stop here
   The answer is subnet of 187.21.32.0

Third Example

Determine the subnet of IP address 12.78.80.80 /14

1. What octet are we working in?
   14 < 16 (the boundry of the 2nd octet)
   Answer: 2nd octet
2. What is the IP address block size?
   16 - 14 = 2
   2 ² = 4
3. How do you build out the IP address blocks?
   12.0.0.0
   12.4.0.0
   12.8.0.0
   12.12.0.0
   (remaining blocks skipped for brevity)
   12.72.0.0
   12.76.0.0
   12.80.0.0 …We can stop here
   The answer is subnet of 12.76.0.0

With this simple technique, you will be determining IP blocks rapidly in no time.  But like anything else, its all about practice.

In order to check your answers, I highly recommend the Online IP CIDR Calculator to help check your answers.

Subnetting host, ip address, Subnetting

CIDR (Classless Internet Domain Routing) is a way to assign IP addresses without using standard IP classes such as A, B, or C.  Using CIDR, IP addresses are displayed using a ‘Slash Notation’ /n where /n is the network prefix.

The network prefix identifies the number of bits that are used to identify a network.  Using the chart below, the network is identified with 1’s and the host is identified with orange colored 0’s.

I color coded the chart to make it easier to see the pattern that develops as the network prefix decreases in its number.  Basically more bits are flipped to become host bits and less are assigned for the network.

Another pattern that can be seen in this chart is in the Netmask.  255, 254, 252, 248, 240, 224, 192, 128 represent the part of the octet assigned to the subnet mask.  Further down the page, is another chart displaying how the resulting numbers come about with decimal to binary conversion.

CIDR - Slash Notation Reference Chart

Decimal - Binary Conversion Chart

Hopefully this layout makes the conversion of decimal to binary for the important numbers in subnet masking easy to memorize.  Each of the 8 bits represent the bits in an octet with the 1st bit being 128 down to the 8th bit being a 1.  Everything is based on the power of 2.

For each ‘1′ bit in an octet , add its decimal equivalents together to get your result.

Subnetting CIDR, decimal to binary conversion, slash notation

I passed the 70-290 exam from Microsoft, Managing and Maintaining a Microsoft Windows Server 2003 Environment.  Scored a 920 out of 1000.  With that done and out of the way, its back to working on the CCNA starting tomorrow.

I plan to take the next two days refreshing my brain with the material I already studied including subnetting.  By the weekend I will commit to a test date and schedule it.

General

While I don’t have any plans to stop the CCNA pursuit, I will be deviating a little bit to work on updating my Microsoft credentials.  Its been awhile since taking a Windows exam.  I am going to put some study time into taking the 70-290: Managing and Maintaining a Windows Server 2003 Environment exam on December 27 during my Christmas vacation.  Prometric and Microsoft have a 2nd chance offer to retake the test for free if not passed on the first try.  I figure why not.  What do I have to loose.  I work with 2003 practically everyday.

This does not mean I’m ending the CCNA route, just delaying it until probably January.  But I will continue to study it in parallel.  My lab is going to get a revamp with a few changes….mixing in Win2k3 domains to span over my routers to act as remote offices / branches for the domain.

I will also continue to post here my CCNA notes as I continue my studies.  I have a couple draft posts waiting to be cleaned up on subnetting and use of RIP v1 and v2.

General

Cisco Feature Navigator is a great site to search for IOS versions available for a router or switch.  The part I find invaluable is the information on the necessary memory needed to load the appropriate IOS.  I have several routers that I’ve picked up over the past week with different amounts of RAM in each.  Over the holiday weekend, I’m planning to upgrade to the best available IOS that I have in my collection based on the memory installed.

General

I have to give credit to the book CCNA Intro Exam Certification Guide by Wendell Odom for the table below. Its a nice condensed view of Layer Names, example protocols and devices relating to those layers.

Study Notes

I’m a very reflective person.  I guess I’m trying to say that I tend to frequently look back a period of time and review what has occurred and analyize the good and the bad.  Hence the reason for this post and the look back at my first week of actually getting myself in gear to get my CCNA completed.

Got a good amount of time in during the work week for reading, labs, and video watching.  Though as I figured, the weekend was a different story.  Between working on the basement, outdoors, a Devils hockey game, my daughters soccer, and a few other things here and there, the weekend is a challenge.

Seems like Sunday night has been the best chunk of time.  This coming week I want to plow through the “dry theory” stuff just to brush up on the OSI layers, TCP/IP and LAN fundamentals.  I’d like to know alot of those topics cold and without having to think about the definitions.  Then hopefully the following week it will be onto routers.

Thoughts

Tweaking the CLI

While this is not exactly a lab pertaining to the CCNA exam, the tips below are a good way to “customize” the command line interface to make it easier to work with.

Logging Synchronous

Session Timeout

Lab Work