Solved try to understand the answer to question

August 1, 2012 at 11:53:20
Specs: Windows 7
A technician is troubleshooting a network connectivity issue with a user's desktop configured to use a static IP address. The technician notes the following configuration:

IP 172.16.2.0
NETMASK 255.255.254.0
DEFAULT GATEWAY 172.16.1.1
DNS 192.168.1.1

Which of the following changes will allow the desktop to communicate properly with remote networks?
a. Changing the DNS to 172.16.1.100
b, Changing the WINS server to 172.17.4.136
c. Changing the netmask to 255.255.255.0
d Changing the default gateway to 172.16.3.1

The answe is Changing the default gateway to 172.16.3.1
.
My question is why do we need to change the default gateway?


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#1
August 1, 2012 at 12:07:46
Did you copy the entire question from the book as it appears there?

I ask because there's a lot of information missing.

For instance, the answer you state as being correct......where did they get 172.16.3.1 from? I see no mention of it anywhere in the question.

While 172,.16.3.1 is part of the 172.16.2.0/23 subnet, there's no where in the question that I see it mentioned as being any kind of a gateway address for any network, much less a remote network.

From what I can see, there is no "right" answer listed because there isn't enough information given in the question.

This is a prime example of a question written by someone who has never worked in industry and has no practical experience in industry. This poorly thought out and poorly written question is sadly pathetic.

I hope for your sake, and that of your classmates, this particular question isn't typical of all your homework questions because if it is, you're going to finish the course you're taking and end up very confused.

It matters not how straight the gate,
How charged with punishments the scroll,
I am the master of my fate;
I am the captain of my soul.

***William Henley***


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#2
August 1, 2012 at 12:40:37
✔ Best Answer
d Changing the default gateway to 172.16.3.1

This is the correct answer, cause you need a working default gateway, to communicate with remote networks.
That's why it's called gateway.
If an ip address is not located in the local network, the default gateway is used to reach the network.
If it's also not reachable by using the default gateway, an error will be returned.


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#3
August 1, 2012 at 12:43:38
But, as CurtR says, what makes you think that 172.16.3.1 is a gateway, working or otherwise, rather than - say - a printer? It might, or might not, be a correct answer. We just don't have enough information to decide.

If this is the level of question asked nowadays on computer science courses then it explains a lot.


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Related Solutions

#4
August 1, 2012 at 13:00:00
I copied the question exactly as it was written

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#5
August 1, 2012 at 14:20:56
If this is the level of question asked nowadays on computer science courses then it explains a lot.

Amen!

I copied the question exactly as it was written

Is this from a text book, or some kind of question sheet your instructor made up themself? I suspect the latter. If the former, I'd request the school change to a different text book.

Here's what I see when I look at the original question you posted:

IP 172.16.2.0
NETMASK 255.255.254.0
DEFAULT GATEWAY 172.16.1.1
DNS 192.168.1.1

First, the IP and netmask combined give you the following network using CIDR notation:

172.168.2.0/23

Here are your available host IP's in that subnet:
First IP: 172.16.2.1
Last IP: 172.16.3.254
Broadcast Address: 172.16.3.255

There is no mention of a router, much less what networks any interfaces on said (missing) router may be on. Ergo the following: DNS 192.168.1.1 is useless and completely meaningless because you can not get to 192.168.1.1 from 172.16.2.0/23 without a router that contains minimum two interfaces with one on each subnet and static routes in between.

Therefore, clients on the 172.16.2.0/23 network CAN NOT communicate with the internet as they have no viable DNS address............period, end of story.

Also, if you take a look at 172.16.2.0/23 you'll see that DEFAULT GATEWAY 172.16.1.1 is not within the subnet so again, it's not a reachable IP address without some kind of a router involved between 172.16.2.0/23 and 172.16.1.1 so clients on 172.16.2.0/23 cannot reach that particular gateway IP and therefore cannot leave their own immediate subnet.

So, essentially, what you have is a closed LAN that has no external access of any kind. Therefore the question cannot be answered using any of the 4 supplied (incorrect) responses.

It matters not how straight the gate,
How charged with punishments the scroll,
I am the master of my fate;
I am the captain of my soul.

***William Henley***


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#6
August 1, 2012 at 14:45:47
The question pertains to understanding supernetting [cidr]

That subnet results in a range of 192.16.2.0 - 192.16.3.255

We know 192.168.1.1 is not valid for anything given the subnet mask. Thats the first clue.

The 2nd clue is the question; access a remote network. We know dns and wins has nothing to do with that. This leaves netmask and gateway.

We eliminate netmask because its doesn't include the ip range required.

This leaves only one answer the gateway which does fall within the subnet scope. Of course it could have been ANY number in the subnet scope range. They made that one easy for you.

Still comes down to knowing your supernetting.

Answers are only as good as the information you provide.
How to properly post a question:
Sorry no tech support via PM's


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#7
August 2, 2012 at 07:27:33
You can only assume that's the correct answer because it's the only IP within the range of the stated 172.16.2.0/23 subnet. As has been pointed out, due to lack of context and information, that IP could actually be any device. In fact, because we have no information, that IP could just as easily be an unused, unassigned address.

With no concrete "proof" that it's a gateway to a remote address, that answer is still wrong in my books. I suspect we'll have to agree to disagree on the veracity of said "correct" answer.

Regardless, I'm sure you can agree that it's an extremely poorly written "trick" question.

In real life, you would have a whole lot more information, and context, to base a decision on. At least I don't base decisions at work on "most likely possibilty" and I wager you don't either.....lol.

It matters not how straight the gate,
How charged with punishments the scroll,
I am the master of my fate;
I am the captain of my soul.

***William Henley***


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#8
August 2, 2012 at 09:44:34
like I said:

"This leaves only one answer the gateway which does fall within the subnet scope. Of course it could have been ANY number in the subnet scope range. They made that one easy for you."

Any ip in the range can be the gateway.

As Spock said: If you eliminate the impossible, whatever remains, however improbable, must be the truth

Answers are only as good as the information you provide.
How to properly post a question:
Sorry no tech support via PM's


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#9
August 2, 2012 at 10:35:52
I know Spock said it in the recent Star Trek movie, but wasn't he quoting Sherlock Holmes?

It matters not how straight the gate,
How charged with punishments the scroll,
I am the master of my fate;
I am the captain of my soul.

***William Henley***


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