As they become more complex and traffic volumes increase, networks take more than great technical skills to design and maintain. So, infrastructure engineers need a designer’s mindset and approach to problem-solving, believes Ethan Banks, senior network architect for Columbus, Ohio-based Carenection and co-founder of Packet Pushers Podcasts. “When I interview candidates, I’m looking for someone who will step outside their comfort zone, dig into problems and design creative solutions,” he says. Click here to find network infrastructure engineering jobs. Here are some of the questions Banks asks to assess a network infrastructure engineer’s technical knowledge and critical thinking skills. You’re designing the routing infrastructure for a large enterprise spread over several campuses, interconnected with a carrier-provided WAN. Would you choose EIGRP or OSPF as the interior gateway routing protocol?

• What Most People Say: Most choose one or the other based on their personal preference and experience. What You Should Say: “Both OSPF and EIGRP are scalable. Both can be configured for equal cost multipath, and both can be tuned for sub-second failover. EIGRP is usually found in heavy Cisco environments. OSPF is found across all networking vendors. However, the choice between OSPF and EIGRP depends on the routing infrastructure requirements and interoperability concerns. I need more information to make a recommendation. May I ask you a few questions?”
• Why You Should Say It: “This isn’t a multiple choice question even though it sounds like one,” says Banks. “Don’t take the bait. Showcase your design mentality and architectural approach by clarifying the situation before recommending a solution.”

Your resume says you're a Spanning Tree expert. What can you tell me about it?

• What Most People Say: “I don’t know how to describe Spanning Tree. We were running it on our network but the consultants set it up.”
• What You Should Say: “Here’s a high-level overview: Spanning Tree is a loop prevention protocol that detects physical loops in an Ethernet network and blocks links to prevent those loops. It should be configured with specific primary and backup root bridges. Spanning Tree comes in several flavors, including rapid and multiple. Rapid per-VLAN generates a unique Spanning Tree per domain, while multiple maps specific VLANs to specific Spanning Tree instances. Spanning Tree ports can be put in various modes, but not all modes are appropriate for all ports. Spanning Tree has various guards that are used to enforce the spanning-tree topology, including root guard and BPDU guard. Would you like me to explain what these guards do and where they should be placed?”
• Why You Should Say It: Experts on specific protocols should be able to explain what the protocol is used for and how it should be deployed. Furthermore, they should be able to describe the protocol’s sub-features, how they should be configured and any major concerns related to using the protocol in a production environment. For instance, they should be able to explain point-to-point mode vs. edge mode. Bottom line, says Banks: “Don’t claim to be an expert unless you really are an expert.”

How do you find answers to difficult questions?

• What Most People Say: “I go to my technical leader for answers when I’m stumped.”
• What You Should Say: “I love a challenge. So I’ll search the Internet, wikis and dig into books when I encounter a difficult problem. In fact, I’ll research every available resource before escalating a problem to someone else in the organization.”
• Why You Should Say It: Technical leaders have enough on their plates. They’re looking for curious and motivated self-starters who want to learn and grow. “Represent yourself as a contributor to ace the interview,” says Banks. “The ability to solve difficult problems and work independently not only appeals to managers, it increases your value as an engineer.”

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