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OSPF LSA and Types of LSAs

As we already know OSPFv2 uses LSAs (Link State Advertisements) as a medium for exchanging data between OSPF neighbors. By using LSAs, OSPF synchronize all routers database. Why we should have deep understanding of OSPF LSAs :-

  1. They are critical for understanding how OSPF works.
  2.  They are always asked in interview.
  3. They contain vital information in and between areas.

So, lets start with the OSPF LSAs. In Total we have 11 LSAs in OSPFv2. They are listed as below.

LSA 1 – Router LSA


LSA 2 – Network LSA


LSA 3 – Summary LSA


LSA 4 – ASBR Summary LSA


LSA 5 – External LSA


LSA 6 – MOSPF LSA


LSA 7 – NSSA External LSA


LSA 8 – Ext Attributes LSA


LSA 9 – Opaque LSA


LSA 10 – Opaque LSA


LSA 11 – Opaque LSA

Note that the LSAs contains the actual data which forms the OSPF database or OSPF LSDB. Since OSPF do not share the prefixes directly, LSA are vital to share the required information.

All the LSAs are shared in LSU packet. For OSPF packets in detail you can visit – OSPF Packets

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