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Link State Update packet:

  • Link State Update (LSU) packets are OSPF message Type 4 in the OSPF header.
  • The local router advertises LSA within an LSU packet to its neighboring routers.
  • LSU is like an envelope which contains multiple LSA’s, which is used in flooding. The local router advertises the LSU with all the missing info in response to the LSR packet.
  • LSA’s are link state advertisement which is used to exchanged information like metric, topology info and many things. There is separate blog on LSA which are explained in much more details with all the necessary information, please refer that blog.

# LSAs- Number of LSAs within an LSU packet (4-bytes)
LSAs- The complete LSA is encoded within this field. The LSU may contain single or multiple LSAs.

The below packet capture shows the content of LSU:

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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