1.  What the Hello packet carries when we enable OSPF?
  2.     What are LSA types?
  3.     What are area types? Why there are different area concepts?
  4.     What is the main importance of STUB network? Why it is been developed in OSPF?
  5.     What will happen if we redistribute between different process ?
  6.     How to generate default route in OSPF?
  7.     How external routes are advertised generally(E1 or E2)? How to change from E2 to E1?
  8.     What are the LSA’s available in STUB and totally stub network?
  9.     What is OSPF super Backbone area?
  10.     What is the concept of auto-cost in OSPF?
  11.     IS there any DR and BDR concept in /31 network?
  12.     What are the different network types in OSPF?
  13.     What are EXSTART and EXCHANGE states? Explain the difference with help of   information exchanged in each state.
  14.     If Router-ID are same between OSPF enabled routers will they form adjacency or not?
  15.     What is LSA 7 and when it is be seen?
  16.     How we can connect a normal area to a backbone area if they are not directly connected?
  17.     Which LSAs are permitted in Totally NSSA?
  18.     Which LSAs are permitted in Stub, Totally Stub, and NSSA?
  19.     How will you generate a default route in an NSSA?
  20.     Kindly explain the concept of Forward-address in OSPF LSA 5.
  21.     What is forward-metric and when is it used on OSPF?
  22.     In which state of OSPF, DR/BDR is elected?
  23.     When does the OSPF router move from Idle to Two-way state?
  24.     What is sham-link. How sham-link helps in preferring the provider-path as primary?
  25.     Explain the loop-avoidance methods using down-bit and domain-tag in MPLS-VPN?
  26.     What is DNA bit in OSPF? Where is it seen in OSPF?
  27.     In which OSPF state a peer stuck if we set the priority 0 on all routers in the shared network?
  28.     How will you filter LSA5 in OSPF?
  29.     Can we filter LSA 1 in OSPF?
  30.     Who generates LSA2 in OSPF?
  31.     Who generates LsA4 and what is purpose of LSA4?
  32.     What indicates an ABR generate to generate LSA4?
  33.     Explain the difference between DBD messages is sent Extart and Exchange state.
  34.     Explain the fields of an LSA hearder.
  35.     Explain the Attempt state in OSPF. When is it seen?
  36.     Can two OSPF routers become neighbors if network-type is different on both ends?
  37.     What is criteria to make two OSPF routers neighbors have different network types?
  38.     How can we set OSPF cost for a Gig or a 10 Gig Link?
  39.     In which LSA do we find V|E|B flags. What are their meanings?
  40.     Explain the difference b/w a STUB area and NSSA besides LSA5 and LSA7s?