Troubleshooting 1

[helpdeskdan]

I got killed on troubleshooting section on the #*@& CIT. (803/804 for those who didn't hear)

Let's say you are telnetting to port 25 to test your email server connectivity. (NOT an actual question on the exam - pls no sue me, no $ anyway - all gone on exam retake) What did you just test - layer 4 right? It's a TCP port. Or, did you? Telnet is layer 7 application - so maybe you just tested through layer 7. See how confusing it gets? I understand the layers and the protocols well, but, a question like this really gets me. It's easy to say that this will verify connectivity to the mail server and that success would mean a defective client. But the answer to a question like this.... ARG!

 

[techkiwi]

Understand where you're coming from, and I don't know if my way of looking at these questions is right or not, but here goes.

When trying to interpret a Cisco question, you have to use every bit of information they provide and look at what you are trying to do at the far-end. So to use your example, if the Cisco question talks about telnetting to port 25 to test your email server, I would say you are testing layer 4, because you're telnetting to a layer four port. You're not working at layer 7, because you are not using the actual email application. You are simply proving that port 25 can be opened.

Although you are using Telnet in this instance, my gut feeling here is that it's NOT layer 7 you're testing, because the telnet application is on the router itself - not at the far-end. And because you're telnetting to a specific port, you're NOT testing telnet itself, but rather that particular port AT THE FAR END. It just so happens you're using Telnet to run this test. The telnet application itself is on the router, so it should just work (unless the router itself is stuffed).

If the Cisco question is looking for an answer of layer 7, I would expect the question to talk more about application-specific information. For example, a user comes to you and complains that her email is not working. Let's take the question two different ways. If the question talks about telnetting to port 25, you're testing at layer four because (as above) you're not testing the actual application. If the question states, "you know everyone else on her LAN segment can use email, which layer would you suspect" then I would pick layer 7. If everyone else on the LAN segment can use email, then the email server is obviously up and working.

Does that make sense?

Graham M. CCNP

 

[helpdeskdan]

Hm... yes, that does make sense. Thanks techkiwi.

 

[lerdalt]

I just found this in the cramsession for CIT (

http://www.cramsession.com/certific...p?product_id=10341&product_type=study+guides)

"Layer 4 - Transport
In this layer, we are primarily concerned with verifying that TCP & UDP can flow, using the port numbers for the applications in question.
-On the End-use system (client)
--As normal HTTP web applications use port 80, you should be able to telnet to the web server in question with port 80. For Example:

telnet

http://www.cramsession.com

80

You should be able to connect to the web server. If this fails, try it with the IP address. If that fails, try to connect to a server on your LAN to see if it is the fault of the router or the Internet connection."

I've just started to read the cramsession for CIT, usually I can pull one or two good pieces of info out of them. Hopefully this is one of them.

TL

 

[helpdeskdan]

Thanks lerdalt! I understand that perfect - it's the way Cisco phrased the question that had me stumped! It drives me nuts; I understand the material perfectly, it's trying to figure out what they are SAYING that is hard!

 

[lerdalt]

I think together we will get through this exam yet. I'm thinking about making another attempt on Friday. I went in kind of cold the first time I took it. Didn't score as well as I'd hoped, but the more I thought of it, the more I realized there was material tested in it that was not covered in anything I had read so far.

So far that was the ONLY thing I pulled out of the cramsession. I've also got the CCIE routing and switching cramsession that I'm going to review before taking the test. Reading the table of contents on it, it looks to be a good review of all the technologies covered in CIT.

Something with ISDN that I pulled out of BCRAN cramsession (am I starting to sound like a broken recored). is the reference points:
R = Rate
S = System
T = Terminal
U = User
V = local Exchange

I haven't come up with a good way to remember them all just yet, but am working on my little 'cheat sheet' for the exam and have it down for now.

I know this isn't going to make any of us feel any better, but I've taken tests from Novell, and they read the same way. Almost like they are trying to confuse you with the wording. I've had a little fun with it between a co-worker and I when we were both working for the CCNA. We'd throw a practice question up on the white board that one of us was having problems. To help him out, I started crossing out the garbage in the question to get down to the key information.

 

[chuck0965]

It is confusing! I think what they are looking for when they ask these type of questions is what's the highest layer you are testing.

Ping tests up to the network layer.
Telnet tests up to the application layer.

 

[helpdeskdan]

That was my original thought. On the CCNA, that would be the correct answer. However, I believe lerdalt and techkiwi are correct in their explanations above.