Interview Hints

[that1guy15]

Oh I am in the middle of them...

If you walk in to Jr level or higher position please know these:

Difference between VLAN and subnet and VTP
Difference between a router and switch and when to use them
What is ARP and explain how traffic makes it from A to B ( so many "CCNPs" dont know this...)
How do you locate a device in your network if given an IP address
What is the difference between a trunk port and access port (cisco land) or non-tagged and multi tagged ports (Everyone else)
What is a LAG or Ether/Port-channel (cisco land). What protocol is used for this.
  Explain the untaged vlan in this.

[NetworkGroover]

Hrmmm... VTP is proprietary to my knowledge.. but a fair question if walking into a Cisco shop.  I wouldn't even run it personally (I think even Cisco recommended configuring all switch in transparent mode?), though I haven't played with VTPv3.  I'd probably break that off as a different question from the diff between a VLAN and subnet...

I think Juniper? doesn't have the concept of a "native" VLAN... at least not directly - think you have to explicitly configure it.  It's been too long I don't remember.

There are two negotiation protocols out there for LAGs .

Those are some good general knowledge questions though.

Some more general knowledge questions I also like to ask:

- If I have a 10G interface, and I add another 10G interface to create a port-channel, did I just double my bandwidth?  Why or why not?

- I need to create an OSPF adjacency across a VLAN trunk.  Is this possible?  Why or why not?

- Explain buffering in a switch.

- What VLANs do routed interfaces on a switch get assigned to?  <<  I like this one a lot.  You get a lot of "Deer-in-the-headlights" looks from that because it just sounds weird.... though I'm not sure if this is specific to a few vendors.

- Bonus just for S&G: What is Cisco's Shared Spanning Tree Protocol and what is it's purpose?  << I didn't find out about this until I started digging into interoperability between vendor's protocols.

[NetworkGroover]

I don't know why I chose to respond to this post this way.... must be the Norco I'm on...

Anyway, yes, you would expect them to know these things... I think the tough part is though in order to even have a decent shot at getting a job in even a Jr. spot it's like you have to have a CCNP.  That puts a lot of pressure on folks to get it knocked out quickly and in turn, possibly not having all the "real world" experience a CCNP should have.  I'll definitely say I fell into that boat.  I'm just really glad I worked at a Web Security company that involved looking at a lot of packet captures which helped a LOT with understanding how things like that worked, or were supposed to work anyway....

[deanwebb]

If you're applying for a security job, please know about recent security breaches and what allowed them to happen.

Also know how to prove it's not the firewall.

[that1guy15]

@AspiringNetworker

Nope all good and valid responses. With me Im not looking for a test answer but what you just provided, a discussion on the subject.

With the past couple rounds of interviews my boss and I decided to shift from a round-robin fire of pointed questions to an open-ended whiteboard session. This keeps the candidate relaxed and fuels more discussion. Which leads to deeper visibility in what they know. The interview is based around asking them to design a network on the whiteboard with a handful of specs. Very open ended and then we throw in questions as we go. Either side of the table can take a subject as deep or shallow as they want.

[packetherder]

@AspiringNetworker

Nope all good and valid responses. With me Im not looking for a test answer but what you just provided, a discussion on the subject.

With the past couple rounds of interviews my boss and I decided to shift from a round-robin fire of pointed questions to an open-ended whiteboard session. This keeps the candidate relaxed and fuels more discussion. Which leads to deeper visibility in what they know. The interview is based around asking them to design a network on the whiteboard with a handful of specs. Very open ended and then we throw in questions as we go. Either side of the table can take a subject as deep or shallow as they want.

Came across a really good article on this recently that cites some research done on the efficacy of various interview techniques. tl;dr of it is unstructured interviews are bad and work-sample tests and structured interviews are good.

http://www.wired.com/2015/04/hire-like-google/

[deanwebb]

We check to see if they can spell TCP/IP. If not, the interview ends then and there.

"Can you spell TCP/IP?"

"Uhh... T..."

"Good."

"Ummm... R?"

"That'll be all for now. Your recruiter will contact you later about next steps. Thanks for coming by."

"Did I get the job?"

"Your recruiter will let you know about next steps. Let me escort you out."

"Wait! The second letter! It's Q! No - it's W!"

"OK, please stop grabbing the table base, or I'll have to call security."

[Nerm]

With the past couple rounds of interviews my boss and I decided to shift from a round-robin fire of pointed questions to an open-ended whiteboard session. This keeps the candidate relaxed and fuels more discussion. Which leads to deeper visibility in what they know. The interview is based around asking them to design a network on the whiteboard with a handful of specs. Very open ended and then we throw in questions as we go. Either side of the table can take a subject as deep or shallow as they want.

As someone that has sat on the other side of the table in the last couple years I completely agree with this form of interviewing candidates. In our industry I think the "20 questions" approach just doesn't work.

@deadwebb haha if you are that hard up for talent maybe I should move to Texas. I hear jobs there pay a whole lot more than in Indiana lol.

[icecream-guy]

I've been giving this alot of thought as of recent.   my knowledge is a mile wide and an inch deep, Although I have a CCNP. I really don't use the technology too much. my current tasks take me working through a wide variety of industry products that I need not touch every day. I may not configure a router or switch for some number of weeks while I am knee deep in in other non-cisco related networking tasks. same for working with Cisco products while I forget how to use the other industry products.

so what I've been pondering, is that although network knowledge is good,  but it's all pretty much based on some sort of standard. Book knowledge is good, but the ability to evaluate and understand traffic flows in the network is more important than any book smarts. Understanding what devices an application communicates with,  the policy based routing, why they are configured and where things are routed to, how the reverse proxy works, and why it is needed, etc.  I think takes on more importance than knowing how to configure LAG groups on Cisco equipment, or knowing how to tell the native VLAN,  or why spanning tree roots are always your oldest slowest switch on the network by default. Things that can be Googled easily.

Reason I've been pondering this is because I just turned 50, make a good salary in networking,and have a few years left on my contract.   I'm scared $hitless, that when the time comes for me to find a new contract in a few years, That I will be overlooked because I can't retain all the details and spout them out during an interview, and some young noob with the book knowledge and half the salary requirements will get the jobs, and I will be forced into early retirement with a lifestyle that I can no longer afford.  The other solution is to remain relevant, making sure that I have knowledge in some modern technologies and can remain desirable in the workforce. But I think that may lock me into a specific technology

So the result of my pondering, where every other technology question answer would be like, yes I used that, I've done that like 8 years ago, and I don't the commands anymore. I don't know how well it would fly in an interview but my take would be more like..In this day and age, with technology so available. makes the ability to google the configuration commands quite easy, the experience I can provide is knowledge of why such configurations are needed, provide alternative solutions, to have and retain knowledge of the network, traffic flows, and applications that the rely on the network to provide the needed services... ( or something like that).

[deanwebb]

To build on Ristau's comments, I know I got my current job at age 45, with only a few months of *recent* network experience and 7 years of generalist IT from 1995-2002, because I was:

* Likable
* Able to show that I know about due diligence, business communication patterns, and other grown-up topics that the kids just don't get
* Able to show that I can troubleshoot my way out of a paper bag, with or without scissors
* Told them that if there was anything new to learn, I was the guy to learn it (See how fast I got my CCNP? That's how fast I learn in real life!)

The biggest key? Likability. There were four other candidates with more experience, but one started an argument in the tech interview and then there were three...

As an oldster, I know that the commands being used today are going to be slightly modified tomorrow and then EVERYONE will be using their Google-Fu to put a config on a switch. Demonstrating that I *can* learn and that I'm eager about being the guy that has to ramp up the fastest on stuff was a big plus.

But, at the end of the day... Likability is king.

[NetworkGroover]

To build on Ristau's comments, I know I got my current job at age 45, with only a few months of *recent* network experience and 7 years of generalist IT from 1995-2002, because I was:

* Likable
* Able to show that I know about due diligence, business communication patterns, and other grown-up topics that the kids just don't get
* Able to show that I can troubleshoot my way out of a paper bag, with or without scissors
* Told them that if there was anything new to learn, I was the guy to learn it (See how fast I got my CCNP? That's how fast I learn in real life!)

The biggest key? Likability. There were four other candidates with more experience, but one started an argument in the tech interview and then there were three...

As an oldster, I know that the commands being used today are going to be slightly modified tomorrow and then EVERYONE will be using their Google-Fu to put a config on a switch. Demonstrating that I *can* learn and that I'm eager about being the guy that has to ramp up the fastest on stuff was a big plus.

But, at the end of the day... Likability is king.

This this this this this.......

As I've said on a previous post, I didn't get hired at my current job because I was an expert who knows all.  I knew enough and displayed a tenacity for learning more, and I was personable.  Like the former VP who interviewed me said, "I tell my guys one simple thing - don't hire assholes."    He also said, "I'll invite an SE to dinner with my family sometimes.  If you can't avoid being awkward at dinner, I'm sure as hell not going to put you in front of a customer."

I'll never forget those statements.  If you're personable (likeable), and show a desire to learn and grow, lack of current skill set usually becomes a non-issue - at least with people interviewing you that know what they're doing.  Unfortunately it won't help you if you're interviewing with some HR recruiter reading off a checklist of questions and doesn't have a clue about networking at all.

Also, yes that1guy15 - open ended questions are the best in my opinion as well.  My last interview was like that and it was actually enjoyable.  It also showed me right off the bat that the company I was interviewing for was legit.

I remember a previous interview where someone asked what the ethertype was for something... I forget.  After admitting that I didn't know, I asked them what it was.  They said, "I don't remember - just curious if you knew!"  Ridiculous.  There were two instances of that in the same interview!

[NetworkGroover]

Reason I've been pondering this is because I just turned 50, make a good salary in networking,and have a few years left on my contract.   I'm scared $hitless, that when the time comes for me to find a new contract in a few years, That I will be overlooked because I can't retain all the details and spout them out during an interview, and some young noob with the book knowledge and half the salary requirements will get the jobs, and I will be forced into early retirement with a lifestyle that I can no longer afford.  The other solution is to remain relevant, making sure that I have knowledge in some modern technologies and can remain desirable in the workforce. But I think that may lock me into a specific technology

I *kinda* know what you mean... and it's even tougher now because I don't think you can really specialize so much anymore.. things are becoming more and more converged.

[AnthonyC]

I remember a previous interview where someone asked what the ethertype was for something... I forget.  After admitting that I didn't know, I asked them what it was.  They said, "I don't remember - just curious if you knew!"  Ridiculous.  There were two instances of that in the same interview!

Heh that's gold.

[NetworkGroover]

I remember a previous interview where someone asked what the ethertype was for something... I forget.  After admitting that I didn't know, I asked them what it was.  They said, "I don't remember - just curious if you knew!"  Ridiculous.  There were two instances of that in the same interview!

Heh that's gold.

Right?  Who does that?

[burnyd]

I think its not even worth asking people technical questions as they can be completely book smart and that is it.

Generally, I will do a phone interview with them and see where they are at.  Why they are leaving etc etc.

I will then do a in person interview and try to grasp what their environment is like then try to ask them what happens if you do this that or this and see how they think.  That is really the best way to find someone who can think and not just copy something into a router and call it a day.  So when it breaks they have to escalate to you because they cannot think on top of their head.