NAT Terms and a Sample ICND1/CCENT Question

Wow - since I reposted on Monday my quick survey of where ya'll want to take the blog discussions, we've had a ton of votes - ok, a relative ton, but a lot more than before - thanks much. No surprise, NAT's still the top vote getter, so I'll focus on NAT for a few weeks - at least the part when I'm blogging. (We'll have a guest next week, but I'll pick it back up the week of October 29th.) Anyway, I think I can fit in a quick ICND1-level question this week, though - I'll post the question today, and get some explanations out there before the week's up.

I built this question to reinforce the concept that the ICND1, ICND2, and CCNA exams today rewards those who both know the facts and can apply the facts. In the old days, the exam might have had a question that just asked "what's the term inside local mean?", with some suggested answers. The question I'm listing today makes you think about those definitions in context, and apply the definitions to the given internetwork, to find the answer. It takes longer if you only understand the basics, which then feeds in to the possible time pressure on these exams.

I've not given you the chance to answer a survey on how long it took you to find your answer, so I'll offer one today. I'd say that you should shoot to meet the goal of 1:10 per question. If you didn't happen to see my blog post from last month in which I (laboriously) gave reasons why that's a good time goal for a multichoice question, feel free to click here. So, here's the poll:

So, here's the question. Although the real exam tells you how many right answers there are, I'll withhold that info, just to make it a little more interesting. OK, start your timers!


In the figure, packet A passes from PC1 to the web server, followed by packet B, which is a return packet sent by the web server to PC1. The figure shows text "A1" and "A2" refer to packet A at two different points in its life, while "B1" and "B2" similarly represent packet B, again at two different points in its life. Router R1 performs source NAT only. Which of the following answers is true regarding these packets?

A) The source address of packet B1 is PC1's inside global address.

B) The source address of packet A1 is PC1's inside global address.

C) The destination address of packet B1 is PC1's inside global address.

D) The source IP address of packet A2 is PC1's inside local address.

E) The destination IP address of packet B2 is PC1's inside local address.

As usual, feel free to post ideas and suggestions, but for the other readers, try not to post the answer in your blog title. That'll help prevent people from seeing the answer so quickly before they get a chance to read the question and take a crack at it. But I'd be interested to hear your thoughts, so post away!


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