Once my resume was shortlisted, they scheduled the first telephonic round. I viewed this interview as an experience, though it was not pleasant.

I had been told to focus on STP/RSTP, L2 switching, and L3 routing. In my resume, I had mentioned that I had worked extensively on routing, multicast, and MPLS protocols. I was first asked to explain my work experience. Next, I was asked if I had worked on Layer 2. I gave an honest reply that I didn't get the opportunity to work with STP or L2 switches. I had told them I was familiar with basic terms, though not at a hands-on level.

They started with a meshed topology of switches, then asked me to explain how a packet traverses. I drew a diagram and began explaining source MAC learning, port VLAN mapping, and then proceeded with store-and-forward (if the entry was found in the table, otherwise flood on all ports). They didn't let me go with my flow; they kept popping more questions. It's acceptable to ask questions when a candidate gets something wrong or pauses and struggles. For example, if I had started to explain the MAC learning of switches (a, d, b, c), they would intervene and ask, 'Tell me the egress port mapping and MAC learning for these switches.' This vibe carried on until I was posed the next question.

My next question was on OSPF packets. I had answered the type of packet and its use. To my surprise, I was told, 'Can you explain it in just one line?' The next question was on the differences between iBGP and eBGP. When I had explained the major loop prevention done in the case of iBGP and eBGP, I was again told I needed a one-line reply.

The next question was again on the same meshed network: 'Explain VLAN-tagged packet traversal in the same meshed network.' Here, they expected me to go into detail and explain. They had asked if ARP was L2 or L3. I had replied that it gets encapsulated in an IP packet (L3) and requires a MAC for learning.

They were done with the interview and asked if I had any questions. I had asked about the role and their responsibilities.

I had an unpleasant experience. I just took this as a learning experience that not all interviewers will make you comfortable and assess your strengths. The matter of getting selected totally depends on four factors: your knowledge, your confidence, your willingness to learn, and the vibe during the process. Even if one fails, we can expect a neutral response.

You may dream of working in a good, helpful, challenging environment. It totally depends on the interviewer nowadays to get an offer. In my career, this was the first unpleasant interview experience. It's good to do self-assessment once the interview is over, no matter if you get selected or not. This helps you in future endeavors :)

1. Given a meshed network of switches with hosts connected, how do end-to-end devices communicate?

OSPFv4 states and packets?

Difference between iBGP and eBGP?