Had technical interview, feeling myself so stupid :/

Today I had a job interview (by phone) for the titled as "Network Engineer".(CCNA level)

First of all, I didn't have too much technical interview experience however I have read quite much about interview questions,books and so on.

I am currently working as a Network Admin(for 7 months,first job, very small company) and feeling(felt) myself pretty confident about "IPSec,L2tp,routing protocols,frame relay concepts, vlan... etc"

However, during interview I was not able to fullfill their expectations probably, and couldn't answer some questions, even some didn't have any idea. Interviewer was not happy from what i guess. I feel myself really bad, stupid. I am a fresh university graduate now and I didn't know i am that bad when it comes to theoretical knowledge.

Some questions and my answers :

What is OSI ?

I explained what is OSI in a very complete way, layer by layer what happens during a communication between 2 computers. I told him that i can go deeper, but he said that it is not necessary.

What is TCP and 3 way handshake

Here I explained again in a complete way, and I even told a little bit about flow control and windowing

What is the maximum packet size you can send in one window ?

Here, I didn't know the answer. And somehow i got stressed (not my style), I said: well i dont remember but MTU is 1500 bytes, for this specific question i will check it out. He said " 65535 bytes"

So if it is 65535 bytes, can u send this size of packet in one window at the beginning ?

Damn! I knew the answer but as a reflection of this stress: I said " why not"

( But of course that's not possible, main idea of windowing is to adjust the size of the sent data by the time which was told by me 10 sec ago to interviewer. So i screwed up!.) He said: " no, your answer is wrong"

Tell me what happens when you ping a computer from another laptop connected to switch (1 switch 2xcomputers)

I nailed it up! I told whole process from ARP to ICMP Echo request to Echo request and ICMP Echo Reply. step by step how it works. he said:"very complete"

What is DHCP ?

I explained what is DHCP, and very detailed definitions of Discover, Offer,request, pack processes. He said" very good"

Port number of DNS?

53, uses udp, sometimes tcp

When udp, when tcp ?

hmm, probably establishes connection with tcp then uses udp. oh no, I think uses tcp when udp is not available. ( he didin't make any comment)

What is vlan?

explained pretty okay.

so, 2 computers at different vlan but same subnet can communicate , or not without a router ?

no, unless if it is not a layer 3 switch ( no comment)

What is vlan frame taggin

I explained pretty well, he said your answer is right

so give me more details about trunking ?

Here he expected me to tell the differences between 802.1q and ISL but I couldnt understand his expectation

He said :"instead of adding additional header and trailer,802.1q embeds a 4 byte vlan id into layer 2 frame header. this increases the size of frame header.

Which ports are used by ftp ?

I said: 20 and 21

When 20 and when 21?

I screwed up again

You can choose any protocol you are good at it and i will ask ?

I said, it is better if he chooses the questions.

What is NAT

I explained what is NAt and what is PAT. and why do we need them. he said okay.

so what is the difference between NATting and routing? i am not asking about the technology behind

Again i couldnt understand his expectation, i felt like i am destroyed... for me those 2 terms are totally different. I explained what is routing and my previous answer was about NAT, but he said thats not what i am asking....

there were some more questions which i dont remember now.... But as a fresh graduate from the university This could be a great chance for me to learn the new technologies. Not everyone finds a chance to work with a Corp. at the beginning. We didin't talk about routing protocols, or STP, or other concepts...Probably that was enough for him to delete me

What are your suggestions and reviews?

P.S English is not my native language. sorry for the mistakes.

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Comments

YFZblu

It sounds like you did a solid job of representing CCNA-level knowledge. I wouldn't stress over one technical interview. You learn and move on. There will be others.

f0rgiv3n

From my previous experience with technical interviews this is usually how they go. The whole goal is to take you as far as you are able to go into a topic. Don't be so hard on yourself, from my point of view (based on what you said in here) you did awesome. And since when is TCP windowing, that deep CCNA level?! I think they were just testing your knowledge to see how wide and deep it is.

Again, don't be so hard on yourself

. If it happens, it happens!

NotHackingYou

Sounds to me like you did very well! Interviewers usually understand nerves play a big part in answers. Don't worry about it!

GOZCU

Thx guys, but this interview was not very good in my opinion. I never asked my self when ftp uses 20 or 21. Looks like i miss some important details here. Or never bothered myself about ISL trunking.

today i have started to read "[h=1]The TCP/IP Guide: A Comprehensive, Illustrated Internet Protocols Reference" by Charles Kozierok[/h]
again thank you, now I feel better. for whole day i felt very guilty

DPG

You did fine.

As an interviewer, I am not as interested in how many facts you can regurgitate as I am in your thought process.

atorven

Like others have said, don't be hard on yourself, you live and learn.

Ivanjam

@GOZCU - I think you did very well! You are being very hard on yourself because of your own high expectations - I doubt the interviewer will be this hard. Good luck on your next endeavor!

GOZCU

Thx guys

I feel myself much much better now

goldenlight

Wouldn't sweat it.. YOu are working in your field and gaining experience..

About7Narwhal

My first technical interview was rough as well, but I got the job. I think they might ask harder and harder questions to see how much you know, measure confidence / competency, and determine if you can apply theoretical knowledge to real world situations. Unfortunately, it is very hard to answer a question correctly when you don't understand it from the start. Job offer or no job offer, interviews are always a great learning experience.

KenC

I don't think you did too badly. The answer on the ftp question was poor though.

grechy

Questions like this

What is the maximum packet size you can send in one window ?
What is TCP and 3 way handshake
Port number of DNS?
Which ports are used by ftp ?
When udp, when tcp

Would have no relevance in the day to day operation of a network. Sure I can think of situations when deep diving into a problem you might check MTU size by using don't fragment ping sweeps or wireshark looking for synack retries but it would be rare. I rarely commit things like common ports into my memory as they can be easily goggled.

100k

I had the same issue today with my phone interview. Don't think I gave the response as well as I knew I could. There are 7 positions to fill and 5 candidates hopping that by some slim chance I get the job. This will be a major for me because this company is known across the world. Hang in there champ

W Stewart

I think your answer were pretty solid for the most part. Unless it's for a real advanced position then I think he may have just been taking the questions a little further to test you and see where you were at but it may not necessarily be his expectation for you to answer them all perfectly. As long as you were clear about your experience and knowledge prior to the interview then I'm sure he got at least everything he expected from the interview. I would say just try not to worry about the interviewing process. You have a network admin gig now so you at least have a little bit more control over your career than if you had nothing and were trying to get your foot in the door. Keep learning as much as you can and making the most of your current position until you get a call back for a better gig.

My first IT interview was much worse. It was the only one I ever went into and completely bombed. I was studying for my CCNA which is why they interviewed me in the first place since it was an ISP. During the interview they started asking me some basic A+ and Net+ level stuff like common port numbers and the event viewer. I had no idea about any of that stuff and I failed that interview horribly. I dropped the Cisco material and got my A+ and Net+ so I would have a good foundation for my career. I've only not gotten the job in two other interviews that I can think of. One of them was because I had no real experience outside of a Dell call center and the other one I can only assume is because it was a NOC job where they said I would be sitting around doing nothing and would only be able to escalate issues to the real admins. I may have come across as too ambitious for that job. They didn't even ask me any technical questions. They just asked me if I understood that green means good and red means bad.

Bottom line is we all get nervous during those first few interviews especially when it might be our big break. You'll get that break so long as you keep learning and gaining experience.

deth1k

What is the maximum packet size you can send in one window ?

65K is the window size negotiated between two hosts, that is not however packet size you will be sending, it still has to be broken down to your MTU size driven by media type i.e ethernet MTU 1500 bytes. Also 65K is common to windows hosts, its much larger on Unix type systems. So your answer would of been right...

Cheers

GOZCU

wow guys, i have learnt a lot from this post here. I was hesitating to write about the interview, good that i decided to share the process.

gbdavidx

isn't network address translation the process of tranlating an external IP to an internal ip and then PAT is when it sends it to the correct the window/application on the computer?

instant000

It shows a lot about your character that you don't want to be unprepared for the next interview.

I also advocate the TCP/IP Guide, if only because it's very low-cost to read online

http://www.tcpipguide.com/

I went through that one around the time I was doing CCNA.

Now I'm going through Volume 1 of TCP/IP Illustrated for a slightly different look at things.

skinsFan202

I'm no longer a big fan of trivia style interviews. Anyone fresh from a certification study period could ace it but it still doesn't tell you much about how effective they could be in your live environment

instant000

skinsFan202 wrote: »

I'm no longer a big fan of trivia style interviews. Anyone fresh from a certification study period could ace it but it still doesn't tell you much about how effective they could be in your live environment

Agreed.

Trivia can get ridiculous.

I've rarely had a day where knowing trivia helped on the job. On the other hand, knowing how things work at a fundamental level comes in handy every single day.

Also, trivia in a phone interview, if the person you're interviewing is unethical, what prevents their looking up the answers?

cisco_trooper

Agree with the above comments. Being an engineer isn't about knowing everything written in some book some guy read. It IS about being able to solve problems that land on your desk. There is a fine balance between all the theoretical junk in books and experience. You need both. If you get out of balance you will start to fail as your experience outweighs your theoretical knowledge or vice versa with your theoretical knowledge outweighing your experience. Also don't forget that the people interviewing you may be inexperienced in their current role, ie. they don't know how to conduct an effective interview yet and may just be doing their best. On the other hand, they may have been doing this for years thinking that this is what they actually need. If I encounter the latter I usually run as it seems to be a key indicator of incompetence within an organization.

Did you get any behavioral type questions? Did they ask you to solve any problems to get a glimpse of your thought process and problem solving skills? Did they ask about past tough situations and how you dealt with them? These are the questions people hate, but they are also very effective in exposing people who padded their resume. I come across a lot of people who can't answer the trivia questions but can still solve problems and get things fixed at a rapid rate. It is all subjective, as much as people try to make it objective, it really never is the case.

kurosaki00

wow they pulled the packet size question lol
do people really memorize that stuff?
Most ppl would say something like its "65k something"

You will always get questions like this
Once I got a question that went like whats the frequency range for the 802.11g or something like that

Maybe its me, but do someone usually know that kind of stuff?
The interview was for a sys admin position, but you had networking duties too like setting up APs
Id like to think like others have said and its just to test how far you can go, and not that they prepare random "prank" questions to see if they can get you

anyways, no worries man. Just keep trying, keep studying, keep applying!

Zartanasaurus

skinsFan202 wrote: »

I'm no longer a big fan of trivia style interviews. Anyone fresh from a certification study period could ace it but it still doesn't tell you much about how effective they could be in your live environment

Ethan Banks agrees with you for that exact reason.

Four Interview Questions I Have Asked Network Engineering Candidates

I think some basic trivia is good for weeding people out in the phone interview phase, but that's about it.

GOZCU

Wohoo ! i have passed the interview ! I do have a face to face interview tomorrow with HR manager

coreyb80

GOZCU wrote: »

Wohoo ! i have passed the interview ! I do have a face to face interview tomorrow with HR manager

Congrats!

lsud00d

Congrats and good luck Gozcu!

I think it's good to be critical of yourself and hopefully this will give you more confidence in your abilities!

charlemagne

GOZCU wrote: »

Thx guys, but this interview was not very good in my opinion. I never asked my self when ftp uses 20 or 21. Looks like i miss some important details here. Or never bothered myself about ISL trunking.

today i have started to read "The TCP/IP Guide: A Comprehensive, Illustrated Internet Protocols Reference" by Charles Kozierok

again thank you, now I feel better. for whole day i felt very guilty

First, I want to say that you have a LOT to be proud of. You state that English is your second language. I've lived in or visited over 17 nations in Europe and realize that it takes a lot of courage and determination (amongst other characteristics) to learn another language as well as you have and network with people in a second language. Do your own research to verify my next statement but: It is a fact in the USA, a sad one, that more often than not it is not the most qualified that get the job but someone else. Hence, the importance of networking amongst people in your target industry as we still live, unfortunately, in a world of "it's who you know, not what you know." Statistics vary but considering that anywhere between 60-90% of communication is NON-verbal (i.e. "body language") many HR managers pick up on subtle things that shouldn't matter but do.
It's easy to doubt oneself. We all do it. Communication in all its forms means so much and often can make a big difference. Really, it's difficult but don't think you did anything "wrong." You know your stuff. If there exists any characteristic to have above all, I would agree with President Coolidge, that it is "Persistence." He said:
"Nothing in this world can take the place of persistence. Talent will not; nothing is more common than unsuccessful people with talent. Genius will not; unrewarded genius is almost a proverb. Education will not; the world is full of educated derelicts. Persistence and determination alone are omnipotent. The slogan "press on" has solved and always will solve the problems of the human race.”
I'm no expert. Yet, I think the ability to believe in yourself (only you really know yourself) along with persistence will, ultimately, pay off and you'll gain valuable wisdom along the way. Good luck!

charlemagne

Just read all the posts and see you have an interview tomorrow.

Good luck!

FloOz

GOZCU wrote: »

Wohoo ! i have passed the interview ! I do have a face to face interview tomorrow with HR manager

Congrats!!! Let us know how it goes

Zartanasaurus

GOZCU wrote: »

Wohoo ! i have passed the interview ! I do have a face to face interview tomorrow with HR manager

Congrats. I didn't think you did poorly on your answers. They weren't perfect, but you definitely displayed some knowledge. You are just hard on yourself, which is a good trait IMO.