technical interviews

All posts tagged technical interviews

I’ve wanted to kick off a series for a while now on technical interviewing. Let me begin with a story.

My first job interview for a full network engineering role was at the San Francisco Chronicle in 2000. I had been working for five years in IT, mostly doing desktop and end-user support. I then decided to get a master’s degree in telecommunications management, which didn’t help at all, followed by a CCNA certification, which got me the interview.

My first interview was with the man who would be my boss. Henry was a manager who had almost no technical knowledge about networking, but I didn’t know that at the time. “Do you know Foundry switches at all?” Henry asked.

“No.” I was already worried.

“I doubted you would. That’s ok because we want to replace them all with Cisco and you know Cisco.” He pulled out a network diagram and handed it to me. “If you look at this, do you see a problem?” he asked.

I had never worked on a network larger than a couple switches, and now I was staring at a convoluted diagram depicting the network of the largest newspaper in Northern California. I was looking at subnet masks, link speeds, and hostnames, trying to find something wrong.

“I’m not sure,” I had to reply meekly.

He pointed at the main core switch for the network. There was only one, with no redundancy.  “There’s a huge single point of failure,” he said. I felt stupid missing the forest for the trees.

Henry brought me upstairs to interview with Tom, who was an on-site project management contractor from Lucent. I was extremely nervous–Lucent (later Avaya) was a big name in the industry and this guy worked for them! Henry left me with Tom. Tom pulled out a copy of the same diagram Henry was showing me earlier.

“Do you notice anything wrong with this?” he asked.

“Wow, that’s a huge single point of failure,” I replied.

He nodded his head in approval. “That’s right–very good.” He asked me a technical question about supernetting. I answered nervously, although it quickly became clear I knew more than he did.

The door flew open and another guy named Vincent walked in. He was the desktop support contractor, but again I didn’t know that. “Ask Jeff a few technical questions,” Tom said.

“Question number one,” said Vincent. “If you were running a network this size, would you subnet it?”

Now the answer seemed obviously to be “yes”, but I was trying to figure out if this is a trick. “Yes,” I answered, deciding to play it safe.

“Good! Next question: Can you route NetBios?” My desktop years were almost exclusively dedicated to Macs and I didn’t even know what NetBios was. I figured it was a 50/50 shot, and the way he asked it seemed to suggest the answer.

“No,” I said, trying to sound confident.

“He’s good,” said Vincent.

Next, the door flew open again, and in walked Bing. Bing was carrying some sort of network device with her. She handed it to me. “Is this a switch or a hub?” she asked. There was no obvious labeling on it, and as I turned the device over and over again in my hands, I had a sinking feeling.

“I don’t know,” I replied.

“Look at this,” Bing said. She pointed to a collision light. “Since there is one on each port, you can tell this is a switch.”

We don’t have collision lights on switches any more, but at the time we did and she had a valid point. Realizing this, I explained to her that a since a hub has a single collision domain, it would only have one collision light. I explained to her the concept of a collision domain, and how a switch worked versus a hub. It turns out she was a project manager for desktop support and she didn’t know any of that. Someone had just shown her the collision light thing and she thought it would be a good question.

“He’s good,” said Bing.

Tom had told me my next interview would be with a CCIE from Lucent. Now that was definitely intimidating. I knew of the reputation of CCIEs, and I didn’t expect to do well. The CCIE guy never showed up. As Tom was walking me to the elevator, however, we ran into him in the hallway. It turns out that Mike, who is still a friend of mine, and who later got three CCIE’s, had not passed the exam yet. We ended up talking about his home lab for a few minutes.

“He’s good,” said Mike. And a good thing too, as I’ve been in a couple of interviews with Mike and I’ve seen him grill people mercilessly.

I got a call with a job offer a few days later, and ended up working there five years.

For a while now I’ve had several posts in my drafts folder on the subject of technical interviewing. As you can see from the above story, interviews are often chaotic, disorganized, and conducted by unqualified people who have no plan. In the case of the San Francisco Chronicle, they made the right decision on me, and I don’t think anybody there would dispute that. I was thankful to begin my career in network engineering.

That said, I’ve had other interviews that didn’t go so well. Over the next few articles, I’d like to cover technical interviewing. Why do we interview people? How can we select good people from bad people? How worthwhile are the typical technical questions? Are gotchas worth throwing out “just to see how the candidate reacts”? Are interviews purely subjective or can we make them data-driven and objective?

I’ll throw out a few more anecdotes from my own experience to illustrate my points–feel free to comment with some of your own!

I feel a bit of guilt for letting this blog languish for a while. I can see from the response to my articles explaining confusing Juniper features that my work had some benefit outside my own edification, and so I hate to leave articles unfinished which might have been helpful. In addition, WordPress is not easy to maintain and I keep losing notifications of comments, which means that when I am not logging in, I miss the opportunity to respond to kind words and questions.

As it is, my work explaining Juniper to the masses will have to be put on hold, as I have left Juniper after six years and returned to my old employer Cisco! I worked at Juniper longer than I had anywhere else, and it’s amazing to consider that I just closed the door on half a decade. But, I even after attaining my JNCIE I always felt like a Cisco guy at heart, and so here I am again. A few random thoughts then:

1. I interviewed for a number of jobs, and now that I am hired I can say that I really hate interviewing. My interviews at Cisco were very fair and reasonable. Just for the heck of it I did a phone screen with Google and completely bombed it. I’m not ashamed to admit that. I’m not supposed to reveal their questions, and I won’t, but they were mostly basic questions about TCP functionality, and MAC/ARP stuff, and it’s amazing how you forget some of the basics over the years. I wasn’t really interested in working there so I did no preparation, and in fact the recruiter warned me to brush up on basics. I just figured my work and blog show that I am at least somewhat technical. I plan to write some posts on the art of technical interviewing, but I was certainly underwhelmed by Google’s screening process, as I’m sure they were by my performance. I really wanted the Cisco job, and what a difference attitude makes! (Oh, and I completely munged an MPLS FRR/Node & Link protection question, less than a year after passing the JNCIE-SP. Uh, whoops.)

2. I bear Juniper no ill will. It was an interesting six years. When I came on board, during the Kevin Johnson years, it was all rah-rah pep talks about how we were going to be the next $10 billion company (errr, no…) followed by a plethora of product disasters. Killing off Netscreen gave the firewall market to Palo Alto, Fortinet, and amazingly resuscitated Checkpoint. Junos Space was a disaster, and Pulse slightly less so. QFabric was not a bad idea, but was far too complex. You needed to buy a professional services contract with the product, because it was too complex to install by itself. And yet it supposedly simplified the data center? There was a fiasco with our load balancer product. And then came the activist investors with their Integrated Operating Plan. I will permanently loathe activist investors. Juniper was hurting and they just magnified the hurt. There’s nothing worse than a bunch of generic business-types who wouldn’t know a router if they saw one trying to tell a router company how to do its business. They thought they could apply the same formula you learn in B-school to any company no matter what it manufactures or does. Then we had the CEO revolving door.

Despite all of this, as I said, I like Juniper. I did ok there, and there are a lot of people I respect working there. Rami Rahim is a good choice for CEO. I left for personal reasons. They still have some good products and good ideas, and I think competition is always good for the marketplace. For the sake of my friends there, I hope Juniper does well.

3. If you read my bio, you will see that I was THE network architect for Juniper IT, meaning I covered everything. This included (in theory at least) campus LAN, WAN, data center, wireless, network security, etc. I did something in all of these spaces. It was a broad level of knowledge, but not deep. That’s why I did my JNCIE-SP–I was hungering to go deep on something. My new job at Cisco is principal technical strategy engineer for data center. This is an opportunity to go deep but not as broad, and I’m happy to be doing that. The data center space is where it’s at these days, and I can’t wait to get deeper into it.

4. Coming back to Cisco after an eight year hiatus was bizarre. It was cool to pull up all my old bugs and postings to internal aliases to see what I was doing back then. Heck, I actually sounded like I knew a thing or two. I was thrilled to find out I am on the same team as Tim Stevenson, whose work as a Cat 6K TME I admired when I worked in TAC. Just for fun I walked though my old building and floor (K, floor 2) and nearly fell over when I saw that it looked identical. I mean, not only the cubes, but there were these giant signs for the different teams (e.g. “HTTS AT&T TEAM”) which were still hanging there as though the intervening eight years had never happened.

Unfortunately, I have to leave a few in progress articles in the dustbin. First, I shouldn’t really be promoting Juniper now that I am working for Cisco. And second, I’ve lost access to VMM, the internal Juniper tool I used to spin up VM versions of Juniper routers. However, I hope to start posting on Cisco topics now that I have access to that gear. Cisco’s products are generally better documented than Juniper’s, but I promise to fill any gaps I might find. And I will leave my previous articles up in hopes that they will benefit future engineers who struggle with Junos.

Onwards!