Preparing for a Network Engineer role in the Service Provider domain?

Here’s a comprehensive list of interview questions.

OSPF:

1️⃣ What is OSPF?

2️⃣ What is the Backbone Area in OSPF, and why is it important?

3️⃣ Why are loopbacks advertised as /32 host routes in OSPF?

4️⃣ What is OSPF’s metric? How is it identified in the routing table? Does it support redistribution?

5️⃣ Explain LSA (Link-State Advertisements) and its types (LSA 1, 2, 3, 4, 5, 7). When do we use LSA type 6?

6️⃣ What is the concept of “auto-cost reference-bandwidth,” and in what scenarios should we use it?

7️⃣ How do you change the reference bandwidth in OSPF?

8️⃣ How does OSPF calculate its metric or cost?

9️⃣ What are the states used in OSPF when forming neighborship?

🔟 What is OSPF Router-ID?

🔷 What are the conditions for forming adjacency in OSPF?

🔷 What are the multicast IPs used by OSPF? What multicast IPs do DR/BDR and non-DR use?

🔷 What are the packet types used by OSPF (e.g., Hello, Dead Timers, LSA, LSU, LSR packets)?

🔷 What is the role of topology and routing tables in OSPF?

🔷 What is the purpose of the link-state retransmit interval, and how is it set?

🔷 What is the purpose of the variable IP-OSPF-Transmit-Delay?

🔷 What algorithm is used by OSPF if equal cost routes exist?

🔷 What is the concept of Virtual-Link in OSPF? Can virtual links be formed through stub areas?

🔷 What is the importance of a stub area? Where is it used, and where is it not used?

🔷 What is NSSA (Not-So-Stubby Area)? Explain its importance.

BGP:

1️⃣ Explain the BGP best path algorithm with a real-time scenario.

2️⃣ What is AS path prepending, and how is it used?

3️⃣ What are BGP states? Why is BGP preferred for large-scale networks?

4️⃣ How do you troubleshoot a BGP adjacency down issue?

5️⃣ Describe BGP path selection criteria.

6️⃣ A router receives the same route from two eBGP peers. How can you prefer one peer over the other?

7️⃣ What is a route reflector, and why is it required?

8️⃣ What happens if a route reflector does not receive proper updates?

9️⃣ What is route dampening, and why is it important?

🔟 Which routes are affected by route dampening?

🔷 What is synchronization in BGP? How is it used?

🔷 How do you troubleshoot when BGP is stuck in the "connect" state?

🔷 What is recursive lookup in BGP, and how does it work?

MPLS:

1️⃣ How many types of VPN exist in MPLS? Explain.

2️⃣ What is MPLS VPN Option A, B, and C? When should each option be used?

3️⃣ What is the concept of penultimate hop popping (PHP), and why is it important?

4️⃣ What is the MPLS label structure?

5️⃣ What are the label types in MPLS Option B and C?

6️⃣ What is the difference between VPNv4 and IPv4 address families?

7️⃣ What is the difference between Route Distinguisher (RD) and Route Target (RT)?

8️⃣ What is VRF Lite?

9️⃣ How many types of routes exist in BGP?

🔟 What is the difference between MPLS VPN Option A, B, and C?