Tejas Networks Network Engineer Interview: Rounds, Questions and Preparation

What the job involves

A Network Engineer in telecom and internet designs, deploys, and maintains IP and optical networks that carry voice, data, and video traffic. Day to day work includes configuring routers and switches, troubleshooting link failures, monitoring network performance, and supporting field teams to keep uptime high. At companies like Tejas Networks, you may work on products such as optical transport gear, broadband access systems, or carrier Ethernet switches.

Role and technical knowledge

1. 1

   Explain the difference between a router and a switch in a telecom network.

   A strong answer covers OSI layer differences (Layer 3 vs Layer 2), how routers forward based on IP and switches on MAC, and gives examples like core routers vs access switches in a carrier network.

2. 2

   What happens step by step when you type a URL in a browser, from a networking perspective?

   Mention DNS resolution, TCP handshake, HTTP request, routing through ISP, and how each layer encapsulates data. Keep it structured and avoid skipping the role of ARP and default gateway.

3. 3

   What is the difference between OSPF and BGP, and where would you use each in a service provider network?

   Explain OSPF as an interior gateway protocol for within an autonomous system, BGP as an exterior gateway protocol for between autonomous systems, and give examples like OSPF in enterprise core and BGP for peering with other ISPs.

4. 4

   What is DWDM and why is it important for telecom operators?

   Cover how DWDM multiplexes multiple wavelengths on a single fiber to increase capacity, its role in long-haul transport, and mention components like multiplexers and amplifiers. Relate it to cost and scalability.

Practical scenarios and troubleshooting

1. 5

   A customer reports that internet is slow but not completely down. How would you troubleshoot this?

   Start with checking interface errors, bandwidth utilization, and latency using show commands. Suggest tools like ping, traceroute, and iperf, and consider duplex mismatch, congestion, or routing loops.

2. 6

   You need to connect two branch offices securely over the internet. What technology would you propose and why?

   Discuss options like MPLS VPN, IPsec VPN, or SD-WAN. Compare cost, security, and performance. A strong answer may recommend IPsec VPN for low cost or MPLS for guaranteed QoS, depending on requirements.

3. 7

   How would you configure a VLAN trunk between two switches and verify it works?

   Explain 802.1Q tagging, trunk port configuration, allowed VLANs, and verification using show interfaces trunk and show vlan. Mention native VLAN and common misconfigurations.

4. 8

   What steps would you take if a fiber link between two sites goes down?

   Describe checking optical power levels, using OTDR if available, verifying physical connections, and testing with loopback. Also mention coordination with field teams and fallback to redundant paths.

Telecom and internet domain awareness

1. 9

   What is the difference between FTTH and DSL broadband?

   FTTH uses fiber to the home for higher speeds and lower latency, while DSL uses copper telephone lines with distance limitations. Mention typical speeds and use cases in Indian context.

2. 10

   What is MPLS and how does it help in traffic engineering?

   Explain label switching, how MPLS directs traffic along predetermined paths, and its use for VPNs and QoS. Mention benefits like fast reroute and traffic engineering in service provider cores.

3. 11

   What are the key differences between 4G and 5G in terms of network architecture?

   Cover 5G's use of higher frequency bands, denser small cells, network slicing, and lower latency. Mention that 5G core is service-based and supports edge computing.

4. 12

   What is the role of a load balancer in a data center network?

   Explain distribution of traffic across multiple servers, health checks, and high availability. Mention common algorithms like round robin and least connections, and layer 4 vs layer 7 load balancing.

Behavioural and HR questions

1. 13

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

   Use STAR format: describe the situation, your specific role, actions taken, and the outcome. Highlight communication and collaboration, especially if it involved a lab project or internship.

2. 14

   Why do you want to work as a Network Engineer in the telecom sector?

   Show genuine interest in networking and telecom, mention exposure to large-scale networks, and connect it to your skills or projects. Avoid generic answers about 'good company'.

3. 15

   How do you handle pressure when a network outage occurs and multiple people are asking for updates?

   Emphasize staying calm, prioritizing tasks, communicating clearly with stakeholders, and following a structured troubleshooting approach. Give an example if possible.

4. 16

   Where do you see yourself in three years in this role?

   Show ambition to deepen technical expertise, take certifications like CCNA or CCNP, and grow into handling complex network designs or leading small teams. Align with the company's growth areas.