Tough interview questions

Unanswered Question
Sep 22nd, 2008

I am not sure if I'm in the right forum but Ill ask all the senior engineers and experts here... If you are going to conduct an interview for an applicant, what are the TOUGH questions you will ask?

Lets say the interview covers the following:


routing protocols


layer 2 questions


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Overall Rating: 3.1 (16 ratings)
compsolv Mon, 09/22/2008 - 19:51

I think that a great one, if you are talking to a candidate that is supposed to be CCNA level, would be:

1 - Describe, in detail, how a host system knows to send traffic to the default gateway, instead of to a local system in an IPv4 network.

2 - Also, describe the layer 2/layer 3 resolution process when a system needs to communicate with another system in a remote subnet of an IPv4 network.

Anthony J. Sequeira, CCIE #15626, CCSI #23251

Senior CCIE Instructor

[email protected]

Internetwork Expert, Inc.

Toll Free: 877-224-8987

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ariesc_33 Mon, 09/22/2008 - 22:18

good questions for a ccna level. how about for the higher level like ccnp, ccip or ccsp?

jim_berlow Mon, 09/22/2008 - 21:38

In our environment, we sit the candidate down in front of a rack of gear and ask them to configure a network that we have drawn on the white board.

We tweak the diagram according to the experience requirements of the job. We don't setup "trick" questions or anything like that, but real tasks that the person may perform on the job. For our entry level candidates, it may be as simple as set up 2 lab PC's on different subnets to ping each other across these couple of routers. For the more advanced interviews, they may be asked to intermingle a couple routing protocols and show bgp configurations. Again, we don't setup candidates to fail but we like to see how they approach network challenges.

We have had great results using this method and it weeds out those who have simply read an article in their fav tech magazine about MPLS.

I hope this helps!


ariesc_33 Mon, 09/22/2008 - 22:23

i wonder if the applicant can browse during the lab config?

because i know that there are good engineers out there that knows what to do but may not know what the exact commands are..

Danilo Dy Mon, 09/22/2008 - 21:47

Very simple, if I need a network engineer, I provide the qualification I need to post in the ad.

The network engineer applying for the job should know the qualification and of course highlight those qualification in their CV.

During the interview, to determine if the applicant really has the qualification I'm looking for (i.e. OSPF), I ask him two or more questions regarding OSPF. To put it simple, I'm asking the applicant questions from what they put in their CV.

If the applicant cannot answer a simple question, they are lying in their CV. I don't want to hire people I can't trust.

dwgray0422 Tue, 09/23/2008 - 04:01

I don't think any of my interview questions are tough, and an applicant who is qualified wouldn't think so either. I'm looking for a qualified individual to hire after the interview not to test them on trivia. I tend to start with a few questions on theory, move on to layer 2 and 3 fundamentals. I don't ask anything that we are not using on a regular basis... (why would they need to understand Traffic Engineering if it's not in use?) I ask straight forward questions, but I look for ease and depth of answer from the candidate.

ariesc_33 Thu, 09/25/2008 - 22:36

this is great! simple questions to be asked but need depth on the candidates answer...

Danilo Dy Tue, 09/23/2008 - 04:38

There are interview also that asks the applicant to solve the problem the interviewee currently experiencing in their network. Even showing the network diagram and some config and debugging output commands. Don't laugh, I did encountered this once as a job applicant. I was offered the job but I didn't take it, I'm not going to work for a company who is so desperate as to ask the job applicant how to solve their current network problem, I view it as unethical :)

davehartburn Fri, 09/26/2008 - 03:39

Give them a login on a cisco router (live if you dare risk it) and ask them to tell you something about it.

I had an interview where they similar with a Solaris box. Apparently they had employed people with certifications in the past, who just could not do the basics.

In such a situation, I'd expect the candidate to probably tell you the model of router before doing a 'show run' and talking through that. They may then go on to tell you who the BGP neighbours are, or something like that. That is why a live router may be better than one sitting on the desk.

babatunde_sanda Sat, 09/27/2008 - 07:09

The question I will put out to you is. How many practising technician/ engineer knows all needed syntax / command lines to get things done always? A good engineer knows how to approach a problem or senario and explain his approach to how he intends to solve it. He necessarily might not remember the commands to get it done. But when he touches the device, he knows what to do. Using only questions to weed out applicants is a big mistake in my opinion. Picking just one of your interview topics. Can you say you know off the top of your head all the commands it takes to configure a site to site vpn tunnel? if you are good you will know the pieces and how to combine them to work not all the syntax and not to mention how diffent it is on various platforms i.e a router versus a pix. If you have to ask just theory I think asking realistic questions as to how he/she will approach a problem or at least things like what will you do to achieve this result is ideal.

Scott Cannon Tue, 09/30/2008 - 20:32

Having interviewed technicians in the past I would suggest you focus on their ability to problem solve, how they approach a problem and how they deal with difficiencies in their knowledge.

If you want to test specific areas of knowledge, have the recruiting agency/your HR dept give them a list of technical questions and forward the responses to you with their CVs.

But in the interview I would suggest laying down problems that are on the easier end of the scale of knowledge you are looking for.

This not only allows you to more clearly evaluate their approach to the problem but also ensures the applicant doesn't get tied up in the minute detail.

I've typically laid out short and concise issues and more often than you might expect, many people still fail to answer all the questions. And sometimes these are the people I've hired.

The asnwer is not the most important issue, the approach to the problem is.


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