Your looking to add staff, a network engineer position, but how can you really tell that the candidate isn’t intentionally or unintentionally misrepresenting themselves from a knowledge or skill set perspective? You could look for those three and four letter acronyms right? I’m talking about the following, CCNP, CCNA, CCIE, CISSP, ACA, ACE, NCTS, NCTE, JNCIA, JNCIE, etc. Well unfortunately I’ve seen far too many folks with some of the previously mentioned certifications that don’t really know how to apply what they’ve learned or don’t have enough experience working with large complex networks. I met a CNE (Certified Novel Engineer) about 10 years ago that was booting a Netware 3.12 server from a floppy disk because he didn’t know how to transfer the MSDOS system files to the hard drive, that’s a true story honest! I will be the first to admit that I don’t personally hold any certifications beyond the claim that I’m a QNE (Qualified Network Engineer). That may or may not change in the future for me personally because I do see some value in holding a few professional certifications from a career growth perspective.
With the current very competitive job market and uncertain economic future employers are wary of taking a chance on new employees and want to be sure that they’ve done their homework. I recently received a few inquiries asking how I grade various candidates for highly technical positions. A few years ago I came up with a few non-vendor specific questions that I use when interviewing potential network engineers. The questions are vendor agnostic and are designed to probe the candidates fundamental understanding of how networking actually works (there’s an idea). Having a list of questions ahead of time allows me to be impartial and focus on the task at hand. I leave all the other issues at hand to the recruiter.
There are no absolute right or wrong answers to many of the questions nor is there any scoring metric… instead it helps me understand how strong a particular candidate is in one area or another. I originally had a question on there asking the candidate to describe a 10Base5 network but quickly realized that not too many of us have actually worked with 10Base5 so I dropped it from the list.
Switching
Q. Describe the different between the FDB/MAC and ARP tables and how they are used.
Q. Describe the differences between 802.1p and DiffServ/DSCP.
(Alternate: describe the differences between L2 and L3 QoS mechanisms)
Q. Describe the difference between a Unicast frame and a Multicast frame.
Q. Describe a broadcast storm and its effect on the network.
Routing
Q. Describe the terms OSPF and BGP and how they are used in IP routing.
Q. Describe a black hole route.
Q. Describe the term latency and it’s affect on networking.
Q. Describe the purpose of protocols such as HSRP/VRRP.
Security
Q. Describe how a stateful firewall works?
Q. Describe how a traditional IPSec VPN works.
Q. Describe a SYN flood attack and its affects.
Q. Describe the term NAT and how it’s used in networking.
Q. Describe a proxy server and how it works.
Optical
Q. Describe the term “dB loss” and its impact to network communications?
Q. What is the difference between singlemode and multimode fiber?
Wireless
Q. How many channels are available in 802.11b 2.4Ghz wireless networks in the USA?
Tools
Q. Describe how traceroute and ping work and how they are used in troubleshooting?
Q. What does SNMP stand for and how is it used in networking?
Other
Q. What is the maximum distance for CAT5 UTP cabling?
Q. Describe the term CIDR and what it’s used for.
Q. What is DHCP and describe its operation in the network.
Q. What’s the network mask for a Class B network in CIDR format?
What do you think? Can you answer the majority of questions above? Are you certified?
Cheers!
Great post. A couple of them stopped me in my tracks, but I felt comfortable with most. I’ll have to go do some reading on those topics that tripped me up a bit.
Do we have your permission to use these questions in part or in whole for our own interviewing purposes? In the next couple of months I’ll be hiring the first person I’ve ever hired and I’ve been trying to figure out a way to gauge their actual knowledge, and these questions are great.
Thanks again.
ChristianT
Hi Christian,
You most certainly have my permission, although I’m not sure that you really need it but it was very nice of you to ask. These questions have served me pretty well over the years although I will admit that I’ve held a few in reserve. Thankfully the folks that I’ve given my recommendation to have all turned out to be very successful.
Thanks for the comment!
We’ve actually taken to a small lab test. Two switches with two laptops serves quite well to test very basic principles like building a trunk or turning POE on a switchport. Even though the goals are very simple, the lab tests a candidate’s ability to learn a new CLI/GUI quickly and gives a good overview of their intuitiveness.
The best thing to see in one of those labs is someone just typing ? and working their way through a CLI. You can certainly learn a lot about someone’s actual thought process by watching them work in an unfamiliar setting.
There’s an idea… might be a little too aggressive for some organizations. How would I react? I would probably start probing the network, seeing what I had access to… suggesting some best practice configuration changes, etc. :)
I know some organizations that have a day long interview processes where they try to asses not just the technical abilities but the personality traits as well. I’ve enjoyed some of those but others left me wanting to literally run for the door.
I do see a problem with how some employers forget to “sell” the job to the candidate. While I understand the current job market is in the favor of the employers you still need to clearly define the job responsibilities and then sell the position to the strongest candidate. I had an interview a few years ago where I walked into a very simple one story office building with cubicles and offices. The offices had folding chairs and card tables… when they asked if I had any questions I should have asked if they bought the chairs and tables new or refurbished.
Cheers!
Michael,
A great post. Like you I once was a QNE, as in the early days you only needed 2/3 years experience to get a good Networking position. A good few years ago I found myself out of work and things had changed significantly, especially in the UK where you need the required certification to just be considered for the position. Luckily enough I had the foresight to get on the certification ladder and once you get through to the interview process then all those years of experience allow you to shine. Now adays when I get the chance and more significantly the time to do a certification, I find that I am always learning something new that I probably would not have had the chance to learn if I was not doing a certification?
CheerZ
You are very correct Flintstone… it’s definitely more about who you know today that what you know.
I think there’s a question in there for a good poll, it’s time to replace that Avaya poll anyway.
Thanks for the comment!
Great post, we just had a CV today that was practically all acronyms and it read like the exam objectives from a Cisco test. CVs like that almost always get rejected as they don’t show that you know how to apply what you’ve learnt
The picture on top of the post is really nice.
You can compare this with your candidates.
In my expierence it is also good to ask about some vendor specific stuff, it shows if somebody really have worked with some equipment or not.
Hi Dominik,
I stumbled across that picture and couldn’t resist… that was probably me at some point in my schooling.
I usually stick to vendor agnostic questions since not many people have worked with Avaya/Nortel equipment.
Cheers!
Often you get some people that are certified at a proffesional level and have no clue about the equipment at that they are certified.
It is very hard to find some candidates that have good skills for the hardware setup you have in your network. Especially if you have some equipment that is not from cisco…..