Components of a Packet

Daniel333

wow, I am on chapter one of the Sybex CCNA 5th edition. To what extent to I have to memorize the components of a frame for the CCNA?

FCS, paritiy bit and their sizes and such. Seem awefully pointless. But then again, I am new to this.

Webmaster

It may seem pointless at first, but it's an important part of the foundation. I wouldn't spend time on memorizing them though, you will get to know them while studying other topics. What you could do, is take a close look a couple of times, and then draw it on a piece of paper, look at the original if you need, and then try to draw it again without looking at the original.

Paul Boz

On the INTRO exam I took this week, I was presented a frame layout and had to ID the frame type based on the included information. So long as you know what parts are in a frame you'll be fine. Just have a general understanding of how it all works and you won't have a problem.

It's definitely work paying atention to, though.

Daniel333

Dang, alright. thanks for the quick replies.

I thought I knew enough to blow through chapter 1, but I guess not. Turns out I generated about 40 flash cards already, now all these.

But my job has said, they will help me work with the routers a little at work. so that should help with my hands on experience. Just gotta get the trivia down.

Paul Boz

When I was reading the Lammle book, I found it helpful to just read the book from front to back, without doing the practice questions or giving anything a second read (unless it was really dense). Then once I was familiarized with the material, I started the chapters over with the objective of actually obsorbing the material. That way, as I progressed through the material I had a general understanding and didn't become overwhelmed. All of the stuff makes a ton more sense when you can sort of see the big picture before you try to really learn everything in detail.

Kaminsky

A great help to my studying of packets and their structure is using a program called Wireshark (formerly known as Ethereal) which is a free packet analyzer. You can get it from http://www.wireshark.org/

Set it to capture on your ethernet card either at home or at work. (you get tons of all sorts of weird and wonderfull packets when you run it at work) Let it run for 30 seconds. Enough for you to open up IE and open a web page or two. Try opening a file on your network, or ping / tracert etc. Then stop the capture and see all the packets that have been coming to and fro.

You can open up individual packets and see the headers of all the different layer encapsulations and the fields in each... Very flexible.. I recomend anyone studying CCNA give it a try.

Really interesting when your learning this topic. Really brings the theory home.


PS: Your not really sniffing the network as you will probably be connected to a switch which means you will only actually be listening to what is happening on your own wire. If you were plugged into a hub you would see everything connected to that hub, etc.

Paul Boz

Ethereal/Wire Shark is a great program for diagnosing what's going on on your network, too. I use wire shark and MRTG to monitor bandwidth on my network. I can give you accurate details about all traffic going through my equipment. It's good to learn the tools used to administer a network early on.