Fastly India Core Network Specialist Interview: Rounds, Questions and Preparation

What the job involves

Core Network Specialists at telecom and internet companies like Fastly India design, deploy, and maintain the high-speed backbone that carries internet traffic. Day to day, they configure routers and switches, troubleshoot BGP and MPLS issues, and monitor network health to ensure low latency and high availability for content delivery. Freshers in this role often start with network operations, incident response, and gradual involvement in capacity planning and peering.

Role and Technical Knowledge

1. 1

   Explain the difference between a router and a switch. Where would you use each in a telecom backbone?

   Cover OSI layers, MAC vs IP addressing, and use cases like core routing with BGP vs access switching in data centers.

2. 2

   What is BGP and why is it critical for an internet company like Fastly?

   Discuss autonomous systems, peering, path selection, and how BGP enables global traffic routing and failover.

3. 3

   How does MPLS work, and what benefits does it offer for telecom networks?

   Explain label switching, traffic engineering, and how MPLS supports VPNs and QoS for latency-sensitive traffic.

4. 4

   Describe the TCP three-way handshake and how it differs from UDP.

   Mention SYN, SYN-ACK, ACK, reliability, and use cases like HTTP (TCP) vs DNS or streaming (UDP).

Practical Scenarios

1. 5

   A customer reports high latency to a specific website. How would you troubleshoot this?

   Outline steps: ping/traceroute, check routing tables, verify BGP announcements, and inspect peering links for congestion.

2. 6

   You notice a BGP session flapping between two routers. What could cause this and how would you fix it?

   Discuss hold timers, MTU mismatches, interface errors, and solutions like adjusting timers or fixing physical links.

3. 7

   How would you design a network to ensure 99.99% uptime for a content delivery network?

   Mention redundancy, diverse paths, anycast, load balancing, and monitoring with automated failover.

4. 8

   What steps would you take if a DDoS attack is overwhelming your network?

   Cover traffic filtering, rate limiting, blackholing, scrubbing centers, and coordination with upstream providers.

Tools and Technologies

1. 9

   Which Linux networking commands do you use to diagnose connectivity issues?

   List tcpdump, netstat, ss, ip, traceroute, and explain what each reveals about packets, sockets, or routes.

2. 10

   How does SNMP help in network monitoring, and what are its limitations?

   Explain polling, traps, MIBs, and limitations like security and scalability, then mention alternatives like NetFlow.

3. 11

   What is the role of DNS in content delivery, and how does anycast improve it?

   Describe DNS resolution, caching, and how anycast routes users to the nearest server for lower latency.

4. 12

   Explain how you would use Wireshark to analyze a slow application.

   Focus on capturing packets, filtering by protocol, identifying retransmissions or delays, and correlating with logs.

Behavioural and HR

1. 13

   Tell me about a time you worked in a team to solve a technical problem.

   Use STAR method: describe the situation, your role, actions taken, and the positive outcome, emphasizing collaboration.

2. 14

   How do you handle stress during a network outage?

   Show calm prioritization, following incident response procedures, communicating clearly, and learning from post-mortems.

3. 15

   Why do you want to work in telecom and internet infrastructure, especially at a company like Fastly?

   Express passion for networking, mention Fastly's edge cloud and CDN work, and align with your long-term growth in the sector.

4. 16

   Are you comfortable with 24/7 shift work and on-call rotations?

   Be honest and positive; mention adaptability, time management, and willingness to learn in a dynamic environment.