The Telephone Interview

A few months ago, I had a telephone interview for a senior networking position. The interview lasted for approximately forty-five minutes, three of us were on the call, me, the company’s technical director and an existing network engineer at the company.  

I have to admit, I stumbled on a couple of the questions they asked me, mostly due to my nerves, and lack of recent interview experience. Here is a review of some of the questions asked, and my responses.  

Q – Tell me a little bit about yourself and how you got into IT?

The opening question and I suppose a good ice breaker. It gets me talking a bit about myself and gives them an idea of how I communicate, how confidently I come across and present myself to customers and colleges should I get the position.  However, having researched this a bit further, it’s far more than that. I’d recommend having a read of the article on, it may help you a lot going forward. 

Q – Tell me why you want this position? 

You know what, I found this one at this stage in the process really hard to answer. I knew little about the company (apart from what had I read from their web site, and gleaned from numerous conversations with the recruiter), the culture, the people, the benefits, or the role and its responsibilities. As with a lot of company websites, there was a whole host of services and software the company provides, however, the interviewers were not that interested in discussing these with me and when I pressed them into why they tended to dodge the question and immediately moved on to more questions for me. 

Q – Describe HTTPS and what it is used for?

Yep, got this one. A communications protocol used to secure communication over computer networks. Commonly used on the internet. 

Q – Would HTTPS secure the information stored within a database?

My answer was no. HTTPS would secure the transmission of data to and from the database across the network, however, once the database has been updated, it’s down to the database technology to secure the data stored within it. 

Q – DNS & records, A, MX, can you have multiple MX records?

Answered this ok, explained what DNS is used for (resolving user-friendly names for computers and services to IP addresses, and vice versa), and described what A & MX records are used for. To follow on from this I was asked if you would ever have multiple MX records? I have to admit I was not sure and explained that the only time I could see this configuration being implemented was for redundancy, if the primary mail server were to fail, the backup could be used by adjusting the records preference. 

Having researched this a little, it seems that you can also use multiple MX records for load balancing. For more information see the following article at 

Q – Explain what the purpose of a DMZ is? 

A physical or logical sub network which exposes a company’s external facing services to an untrusted network.  

Q – What would you typically place in a DMZ?

Mail servers, Web servers, FTP servers, & VoIP Servers. 

Yes, answered this one, have to admit I did not mention VoIP servers, however, I listed the other three.  

Q – What is VLAN tagging and what would you use it for? 

Okay, I stumbled on this one and my answer was rather vague, however having done some research post interview, here is what my answer would and should have been. 

VLAN tagging is used to identify which VLAN a packet is destined for. A Tag is added to a packet when it traverses a trunk link, and removed at the end of the trunk link and forwarded to the correct link port on the switch. The tag is removed so that the receiving end is unaware of any VLAN information. 

The website has a very good article on VLAN tagging, which is well worth a read.

Q – Tell me about the two parts to a VPN tunnel and why would you use an aggressive VPN? 

Well, VPN was bound to come up, after all being able to setup and debug a VPN is a network engineer bread and butter. So, I answered this one ok, explained phase 1 and phase 2 of the VPN tunnel and what happens at each phase. I did struggle with explaining an aggressive VPN, just something I’d not come across or configured before. 

Having researched this post interview, main mode or aggressive mode is configured at phase 1. Main mode is most common and is more secure, as the two peers exchange identities with encryption. With aggressive mode, the peers do not use encryption, hence it’s faster but less secure. Aggressive mode is commonly used when one or both of the peers have dynamic IP addresses. 


Make no mistake, this was a tough interview, a technical grilling. I came off the phone exhausted, the call only lasted forty-five minutes but if felt like longer. Looking back now though, it was a great experience, and I don’t think I will get another telephone interview tougher than this. Next time I’ll be better prepared, have some of the generic questions answered, and I’m up for the challenge. Writing about the experience will keep it fresh in my mind, and I’ll always have it available as a reference, one of the main reasons for starting this blog in the first place. 

Thanks for reading 

TSP Admin