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OSPF Packets : LSR

Let’s continue to dive deep in the remaining packets:

LSR:

  • LSR i.e. Link state request packet is used to request a specific prefix or route which is not present in the Link State Database.
  • LSR is type 3 message inside OSPF header as highlighted below
  • Once the DBD are exchanged and Database is compared, OSPF routers uses this LSR to request the missing info which is not present in its own Database.

The below is LSR header format:

LS Type- Type of LSA requested (4-bytes)
Link State ID- Depends upon the type of LSA (4-bytes)
Advertising Router- Router ID of the requesting router (4-bytes)

The following packet capture shows the LSR sent for Router-LSA (Type-1) to an OSPF neighbor after DBD packet exchange process is over.

For more detailed understanding LSA, please check the separate blogs on each and every LSA’s at ipinbits.com/knowledge-base

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